OsPLS4 encodes aβ-ketoacyl carrier protein reductase(KAR).The role of OsPLS4 in rice sheath blight(Rhizoctonia solani)remains unclear.Our preliminary studies showed that premature leaf senescence mutants(pls4)were hi...OsPLS4 encodes aβ-ketoacyl carrier protein reductase(KAR).The role of OsPLS4 in rice sheath blight(Rhizoctonia solani)remains unclear.Our preliminary studies showed that premature leaf senescence mutants(pls4)were highly susceptive to sheath blight in the early stage of rice development.To explore the role of this gene in the development of rice sheath blight,the transcriptome profiles of the rice pls4 mutant and wild type were compared by RNA-seq.The results revealed 2,569 differentially expressed genes(DEGs).The down-regulated genes were significantly enriched in the defense response-related biological processes.These down-regulated genes included the chitinase genes and WRKY genes,which were significantly changed in pls4 mutants.Furthermore,467 genes induced significant alternative splicing(AS)events.Among them,intron retention(IR)affected gene expression levels and functions of the vitamin B6(VB6)metabolism pathway related to sheath blight.This result suggests that IR plays an important role in the sheath blight resistance of mutant pls4.Together,these results indicate that pls4 could be involved in the biological process of sheath blight via DEGs and the fine-tuning of IR.The present study provides a molecular basis for further investigation of the resistance of rice to sheath blight.展开更多
Sheath blight, a disease caused by the fungus Rhizoctonia solani Kuhn (anamorph), has been the most economically significant disease of rice. It was frequently reported that the disease was well-controlled in integr...Sheath blight, a disease caused by the fungus Rhizoctonia solani Kuhn (anamorph), has been the most economically significant disease of rice. It was frequently reported that the disease was well-controlled in integrated rice-duck system without the employment of fungicides. However, the effecting factors behind this phenomenon were rarely reported. In this research, experiment was carried out between two treatments, rice combined with ducks (RD) and conventional rice field without ducks rearing (CK) in early season rice paddy, to investigate the variations of sclerotia in floodwater and on rice plant, microclimate 10 cm above the waterline in rice paddy and activity of protective enzymes in rice plants. The results showed that the floating sclerotia in floodwater in RD was 86-91% lower than that in CK, and adhering sclerotia in rice plant in RD was 67-78% lower than that in CK. The relative humidity tested significantly lower and light intensity tested significantly higher in RD. The temperature in the early rice growth stages in RD was slightly lower than that in CK, but it was significantly higher (32.3-36.5~C) in the middle stage rice growth stages. The polyphenoloxidase (PPO) activity in RD were lower than that in CK, but the enhanced activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and Chitinase was observed in different stages of rice growth in RD, especially the Chitinase which showed higher activity in all investigating days.展开更多
Eight compounds were isolated from the fermentation cultures of rice sheath blight pathogen Rhizoctonia solani Kuhn. They were identified as ergosterol (1), 6β-hydroxysitostenone (2), sitostenone (3), m-hydroxy...Eight compounds were isolated from the fermentation cultures of rice sheath blight pathogen Rhizoctonia solani Kuhn. They were identified as ergosterol (1), 6β-hydroxysitostenone (2), sitostenone (3), m-hydroxyphenylacetic acid (4), methyl m-hydroxyphenylacetate (5), m-hydroxymethylphenyl pentanoate (6), (Z)-3-methylpent-2-en-1,5-dioic acid (7) and 3-methoxyfuran-2-carboxylic acid (8) by means of physicochemical and spectroscopic analysis. Among them, 2, 3, 5-8 were isolated from R. solani for the first time. All the compounds were evaluated for their biological activities. 4-6 and 8 showed their inhibitory activities on the radical and germ elongation of rice seeds. 1,4 and 7 showed moderate antibacterial activity to some bacteria. 4, 7 and 8 exhibited weak inhibitory activities on spore germination of Magnaporthe oryzae. 8 showed moderate antioxidant activity with the 1,1-diphenyl-2-picryhydrazyl (DPPH) andβ-carotene-linoleic acid assays. This is the first time to reveal compounds 5, 6 and 8 from rice sheath blight pathogen R. solani to have in vitro phytotoxic activity.展开更多
To construct the T-DNA insertional mutagenesis transformation system for rice sheath blight pathogen Rhizoctonia solani AG-1 IA,the virulent isolate GD118 of this pathogen was selected as an initial isolate for transf...To construct the T-DNA insertional mutagenesis transformation system for rice sheath blight pathogen Rhizoctonia solani AG-1 IA,the virulent isolate GD118 of this pathogen was selected as an initial isolate for transformation.The conditions for transformation of isolate GD118 were optimized in five aspects,i.e.pre-induction time,co-culture time,acetosyringone(AS) concentration at the co-culture phase,co-culture temperature and pH value of induction solid medium(ISM) at the co-culture phase.Finally,a system of Agrobacterium tumefaciens-mediated transformation(ATMT) for R.solani AG-1 IA was established successfully.The optimal conditions for this ATMT system were as follows:the concentration of hygromycin B at 30 μg/mL for transformant screening,8 h of pre-induction,20 h of co-culture,200 μmol/L of AS in ISM,co-culture at 25 ℃ and pH 5.6 to 5.8 of ISM at the co-culture phase.The transformants still displayed high resistance to hygromycin B after subculture for five generations.A total of 10 randomly selected transformants were used for PCR verification using the specific primers designed for the hph gene,and the results revealed that an expected band of 500 bp was amplified from all of the 10 transformants.Moreover,PCR amplification for these 10 transformants was carried out using specific primers designed for the Vir gene of A.tumefaciens,with four strains of A.tumefaciens as positive controls for eliminating the false-positive caused by the contamination of A.tumefaciens.An expected band of 730 bp was amplified from the four strains of A.tumefaciens,whereas no corresponding DNA band could be amplified from the 10 transformants.The results of the two PCR amplifications clearly showed that T-DNA was indeed inserted into the genome of target isolate GD118.展开更多
The transgenic rice, Zhongda 2, which was genetically modified from an indica rice line Zhuxian B by rice chitinase gene (RC24), had high resistance to rice sheath blight (Rhizoctonia solan!) in laboratory and a two-y...The transgenic rice, Zhongda 2, which was genetically modified from an indica rice line Zhuxian B by rice chitinase gene (RC24), had high resistance to rice sheath blight (Rhizoctonia solan!) in laboratory and a two-year field experiment. The pathogen could invade sheath of Zhongda 2 and induce symptoms of the disease. No difference was noted in time of penetration or incubation period between Zhongda 2 and non-transgenic rice control, Zhuxian B, but the hyphae lysate could be observed earlier than control. Its resistance expressed as to inhibit the growth of mycelium in host tissue. Fis from Zhongda 2(4) crossed with other five non-transgenic rice lines showed higher resistance than donor non-transgenic parents, but the resistance was different along with the different maternal parents.展开更多
To establish a standard system for geneticstudies on sheath blight resistance, a field testwas conducted at the experimental farm ofYangzhou University to compare several pro-cedures for inoculating rice plants with R...To establish a standard system for geneticstudies on sheath blight resistance, a field testwas conducted at the experimental farm ofYangzhou University to compare several pro-cedures for inoculating rice plants with R.solani Kuhn (RH9). The varieties used wereJasmine 85, Teqing (resistant or moderatelyresistant), and Lemont (susceptible). They展开更多
Trehalose metabolism is related to the sclerotial development of Rhizoctonia solani AG-1 IA,the causal agent of rice sheath blight(RSB).Here,we further elucidated the functions of three genes Rstre,Rstps1 and Rstpp th...Trehalose metabolism is related to the sclerotial development of Rhizoctonia solani AG-1 IA,the causal agent of rice sheath blight(RSB).Here,we further elucidated the functions of three genes Rstre,Rstps1 and Rstpp that encode three key enzymes trehalase(TRE),alpha,alpha-trehalosephosphate synthase(TPS1)and trehalose 6-phosphate phosphatase(TPP)in the sclerotial development of R.solani AG-1 IA.Due to the lack of a stable genetic transformation system for R.solani,the heterologous expression of these three genes in Pichia pastoris GS115 was performed.The results showed that reactive oxygen species(ROS)contents and enzyme activities in R.solani decreased significantly in the treatments of the fermentation broths of Rstps1 and Rstpp transformants,and that in the treatment of the fermentation broth of Rstre transformant visibly increased.Furthermore,the fermentation broths of the transformants of all the three genes were added to potato dextrose agar(PDA)medium for the cultivation of R.solani,as a result,the dry weight of sclerotia in each PDA plate containing the fermentation broths of Rstps1 and Rstpp transformants significantly increased compared with the control,and that of Rstre transformant obviously decreased.Finally,178 proteins were found to interact with RSTPS1,and 16 of them were associated with ROS.Taken together,the findings suggest that all these three genes related to trehalose metabolism play important roles in the sclerotial development of R.solani AG-1 IA,and can be used as new targets for the development of novel high-efficiency fungicides for the controlling of RSB.展开更多
Antagonistic bacterial strain 91-b possessedstronger antagonistic ability against SHBinfection. The control effects of the bacterizationagainst SHB were 58.1% in greenhouse and 45.1%in paddy. The effect of antibiosis ...Antagonistic bacterial strain 91-b possessedstronger antagonistic ability against SHBinfection. The control effects of the bacterizationagainst SHB were 58.1% in greenhouse and 45.1%in paddy. The effect of antibiosis JK-91-b exudat-ed by strain 91-b was studied in the present re-search.Bacterial strain 91-b was inoculated into展开更多
We have recently developed a systematic method for the study on the inheritance of resistance to sheath blight. The key of the system is an innovated method of inoculation and investigation along with the employment o...We have recently developed a systematic method for the study on the inheritance of resistance to sheath blight. The key of the system is an innovated method of inoculation and investigation along with the employment of the permanent population. This paper reported the procedure of the system and the result of its verification.展开更多
Sheath blight (SB) caused by Rhizoctonia solani is one of the three major diseases of rice, and now has become the most severe disease causing rice yield loss in China. Breeding and use of varieties resistant to SB ...Sheath blight (SB) caused by Rhizoctonia solani is one of the three major diseases of rice, and now has become the most severe disease causing rice yield loss in China. Breeding and use of varieties resistant to SB is crucial in controlling the disease, but the advances achieved have been limited due to the tack of highly SB-resistant rice germplasm. Genetic analysis revealed that the SB resistance in rice was a typical quantitative trait controlled by multi-genes. Although many QTLs conferring resistance to SB have been identified in recent years, most of the QTLs only showed small effects and few of them have been evaluated for utilization potential. Many R. solani-resistant resources have been found in wild rice species, microorganisms and other plant species. It is already known that the SB-resistance could be improved in transgenic rice plants by genetic transformation. This paper reviewed the genetic mapping of loci associated with resistance to rice SB, the evaluation of the potential of resistance QTLs, and the resistant resources found in various organisms besides rice. To develop SB-resistant rice varieties, it is important to develop and explore new resistant rice germplasms, fine map and evaluate resistance QTLs, and also to pay attention to various bio-resources showing resistance to R. solani.展开更多
The control effects of six kinds of reagents against rice sheath blight were compared in the test. The results showed that 24% thifluzamide SC 300 mL/hm2 and 20% Jinggangmycin ~ prochloraz WP 750 g/hm2 had good contro...The control effects of six kinds of reagents against rice sheath blight were compared in the test. The results showed that 24% thifluzamide SC 300 mL/hm2 and 20% Jinggangmycin ~ prochloraz WP 750 g/hm2 had good control effect against rice sheath blight, and their control effects after spraying for 7 and 14 d were 72.16%, 77.91% and 66.52%, 71.08%, respectively. The control effects of both reagents were significantly better than other test reagents and control re- agent Jinggangmycin, and they had no adverse effect on growth and development of rice. Considering from the aspects of control effect and economy, 20% Jinggang- mycin ~ prochloraz WP was suggested to be used to control rice sheath blight, its recommended dosage was 600 -750 g/hm2, and the reagent volume was 750kg with coarse spraying.展开更多
Rice sheath blight,caused by Rhizoctonia solani(Kühn),is a notorious soil-borne disease prevalent in many rice-growing regions.Although several sporadic studies of mycoviruses in R.solani AG-1 IA have been report...Rice sheath blight,caused by Rhizoctonia solani(Kühn),is a notorious soil-borne disease prevalent in many rice-growing regions.Although several sporadic studies of mycoviruses in R.solani AG-1 IA have been reported for single strain of R.solani AG-1 IA,there have been no reports describing the distribution and diversity of mycoviruses in natural populations.In this study,43 R.solani AG-1 IA strains collected from different locations in China were examined for the presence of ds RNA elements to confirm the presence of viral infections.Electrophoretypes showed that 16 of the 43 fungal strains(37.2%)contained ds RNAs that can be characterized as viruses.Furthermore,the species-specific reverse transcription PCR(RT-PCR)showed ds RNA bands with similar sizes do not always contain the same virus but exist as mixed mycoviral infections.Thus,our findings indicate mycoviruses infecting R.solani AG-1 IA in China are diverse,widespread and universal.展开更多
Sheath blight of rice, caused by Rhizoctonia solani AG 1. 1a, has become the most important disease and caused serious yield losses in some major rice-growing regions in China in recent years. In the present study, fi...Sheath blight of rice, caused by Rhizoctonia solani AG 1. 1a, has become the most important disease and caused serious yield losses in some major rice-growing regions in China in recent years. In the present study, field plot experiment was conducted to examine the relationships between disease intensity and inoculum density (ID), the seasonal disease epidemic dynamics, and yield reductions due to disease damages. Results from the experiment demonstrated that the areas under progress curves of disease severity and those of percent rice tillers diseased were positively and closely related to the relative initial ID of the pathogen. The inoculum density-disease (IDD) relationships were simulated and the impractical linear models were obtained. Both logistic and Gompertz functions could be used to simulate the disease progress dynamics in time, but the progress curves of the disease severity were modeled better by the Gompertz than by logistic function. However, the Richards function was found to be the best in simulating the disease progress curves when a most appropriate value was chosen for the shape parameter m by using the computer software Epitimulator. Sheath blight infection decreased rice yield very significantly and a yield reduction of 40% was recorded in rice crop with the highest inoculum density. Rice yield was linearly and negatively correlated with the disease severity and the percent tillers affected. The simulated models for all these relationships were computed through executing Epitimulator software and were presented in this paper.展开更多
Rice sheath blight pathogen,Rhizoctonia solani,produces numerous sclerotia to overwinter.As a rich source of nutrients in the soil,sclerotia may lead to the change of soil microbiota.For this purpose,we amended the sc...Rice sheath blight pathogen,Rhizoctonia solani,produces numerous sclerotia to overwinter.As a rich source of nutrients in the soil,sclerotia may lead to the change of soil microbiota.For this purpose,we amended the sclerotia of R.solani in soil and analyzed the changes in bacterial microbiota within the soil at different time points.At the phyla level,Proteobacteria,Acidobacteria,Bacteroidetes,Actinobacteria,Chloroflexi and Firmicutes showed varied abundance in the amended soil samples compared to those in the control.An increased abundance of ammonia-oxidizing bacterium(AOB)Nitrosospira and Nitrite oxidizing bacteria(NOB)i.e.,Nitrospira was observed,where the latter is reportedly involved in the nitrifier denitrification.Moreover,Thiobacillus,Gemmatimonas,Anaeromyxobacter and Geobacter,the vital players in denitrification,N2O reduction and reductive nitrogen transformation,respectively,depicted enhanced abundance in R.solani sclerotia-amended samples.Furthermore,asymbiotic nitrogen-fixing bacteria,notably,Azotobacter as well as Microvirga and Phenylobacterium with nitrogen-fixing potential also enriched in the amended samples compared to the control.Plant growth promoting bacteria,such as Kribbella,Chitinophaga and Flavisolibacter also enriched in the sclerotia-amended soil.As per our knowledge,this study is of its kind where pathogenic fungal sclerotia activated microbes with a potential role in N transformation and provided clues about the ecological functions of R.solani sclerotia on the stimulation of bacterial genera involved in different processes of N-cycle within the soil in the absence of host plants.展开更多
[ Objective] The paper was to confirm the best application period and frequency of 75% trifloxystrobin ·tebuconazole WG against rice blast and rice sheath blight. [ Method] Influences of different dosages and dif...[ Objective] The paper was to confirm the best application period and frequency of 75% trifloxystrobin ·tebuconazole WG against rice blast and rice sheath blight. [ Method] Influences of different dosages and different application periods of 75% trifloxystrobin · tebuconazole WG on control effects against rice blast and rice sheath blight, as well as their effects on rice yields were studied in the paper. [Result] The control effects of three different fungicides application treatments against rice sheath blight were 80.24%, 83.0% and 67.99%, and the control effects against rice blast were 56.4%, 49.11% and 61.1%, respective- ly. Advanced application of fungicide for two times had good prevention effect against rice sheath blight ; properly delayed application of fungicides for two times was conducive to improving the control effect against rice blast, and one time application of sufficient fungicide during middle booting stage had higher control effect than application for two times. Effective panicle number per unit area, total grain number, 1 000-grain weight and moisture content of various fungicide application treat- ments did not have significant difference with those of the treatments without fungicide application, but grain number per panicle in treatments applied with fungicide was higher than the treatment without application. [ Conclusion] 75% Trifloxystrobin ·tebuconazole WG has better control effect on rice blast and sheath blight, which helps to promote the formation of rice grain and increases yield significantly. The fungicide application against rice sheath blight should be appropriately ad- vanced, and application for one time against panicle blast after middle booting stage is helpful to improve the control effect.展开更多
Rice sheath blight disease (ShB), caused by Rhizoctonia solani, gives rise to significant grain yield losses. The present study evaluated the efficacy of Integral, the commercial liquid formulation of Bacillus subti...Rice sheath blight disease (ShB), caused by Rhizoctonia solani, gives rise to significant grain yield losses. The present study evaluated the efficacy of Integral, the commercial liquid formulation of Bacillus subtilis strain MBI 600, against rice ShB and for plant growth promotion. In greenhouse studies, four log concentrations of Integral (from 2.2×10^6 to 2.2×10^9 cfu/mL) were used as seed treatment (ST). After 25 d, seedlings were dipped (SD) into Integral prior to transplanting. At 30 d after transplanting (DAT), leaf sheaths were inoculated with immature sclerotia of the pathogen. At 45 DAT, a foliar spray (FS) with Integral was applied to some treatments. The fungicide control was 50% carbendazim at 1.0 g/L, and a nontreated control was also included. Overall, there were 10 treatments, each with five replications. ShB severity was rated at 52 DAT, and seedling height and number of tillers per plant were rated at 60 DAT. In 2009, two field trials evaluated Integral at 2.2×10^8 and 2.2×10^9 cfu/mL. Integral was applied as ST, and seedlings were produced in a nursery bed. After 32 d, seedlings were treated with Integral as SD and transplanted into 10 m^2 blocks. Foliar sprays were given at 45 and 60 DAT. There were seven treatments, each with eight replications arranged as a factorial randomized complete block design. At 20 DAT, the plots were broadcast inoculated with R. solani produced on rice grains. Seedling height before transplanting, ShB severity at 90 DAT, and grain yield at harvest were recorded. Integral at 2.2×10^9 cfu/mL provided significant increase of seedling heights over other treatments under greenhouse conditions. The Integral treatments of ST + SD + FS at 2.2×10^9 cfu/mL significantly suppressed ShB over other treatments. In field studies, Integral provided significant increase of seedling height in nursery, and number of tillers per plant, compared with the control. ShB severity was significantly suppressed with higher concentrations of Integral compared to lower concentrations. Grain yield were the highest at an Integral concentration of 2.2×10^9 cfu/mL. Overall, Integral significantly reduced ShB severity, enhanced seedling growth, number of tillers per plant and grain yield as ST + SD + FS at the concentration of 2.2×10^9 cfu/mL under the conditions evaluated.展开更多
Sheath blight(SB) caused by the soil borne pathogen Rhizoctonia solani is one of the most serious global rice diseases. Breeding resistant cultivar is the most economical and effective strategy to control the disease....Sheath blight(SB) caused by the soil borne pathogen Rhizoctonia solani is one of the most serious global rice diseases. Breeding resistant cultivar is the most economical and effective strategy to control the disease. However, no rice varieties are completely resistant to SB, and only a few reliable quantitative trait loci(QTLs) linked with SB resistance have been identified to date. In this study, we conducted a genome-wide association study(GWAS) of SB resistance using 299 varieties from the rice diversity panel 1(RDP1) that were genotyped using 44 000 high-density single nucleotide polymorphism(SNP) markers. Through artificial inoculation, we found that only 36.5% of the tested varieties displayed resistance or moderate resistance to SB. In particular, the aromatic and aus sub-populations displayed higher SB resistance than the tropical japonica(TRJ), indica and temperate japonica sub-populations. Seven varieties showed similar resistance levels to the resistant control YSBR1. GWAS identified at least 11 SNP loci significantly associated with SB resistance in the three independent trials, leading to the identification of two reliable QTLs, qSB-3 and qSB-6, on chromosomes 3 and 6. Using favorable alleles or haplotypes of significantly associated SNP loci, we estimated that both QTLs had obvious effects on reducing SB disease severity and can be used for enhancing SB resistance, especially in improving SB resistance of TRJ sub-population rice varieties. These results provided important information and genetic materials for developing SB resistant varieties through breeding.展开更多
Rice resistance to sheath blight (SB) is controlled by polygenes or quantitative trait loci (QTLs) and affected by plant morphological traits, qSB-9^TQ and TAG1^TQ, which control SB resistance and tiller angle (T...Rice resistance to sheath blight (SB) is controlled by polygenes or quantitative trait loci (QTLs) and affected by plant morphological traits, qSB-9^TQ and TAG1^TQ, which control SB resistance and tiller angle (TA), respectively, were employed to test whether the combination of the two genes will further improve rice SB resistance and reduce yield loss rather than only one of them or neither. Using two pairs of near isogenic lines (NILs), TAC1^TQ was confirmed to contribute to SB resistance. However, its effect was less considerable than that of qSB-9^TQ. Subsequently, the two genes were introduced into two commercial rice varieties to develop a series of NILs. The NILs carrying both TAG1^TQ and qSB-9^TQ showed more resistance than the NILs containing only one of them. Comparing the grain yield per plant (GYP) under the three different SB disease conditions, namely slight, moderate and severe conditions, NILs carrying both genes apparently lost lower GYP than the NILs without the two genes and the NILs carrying only TAC1^TQ. Under slight disease condition, no significant differences were found on morphology, development and GYP associated traits except for TA between the NILs carrying both genes and either of them, indicating that the two genes have no inferior effect on rice agronomic traits. Results indicated that mAC1^TQ and qSB-9^TQ have high breeding potential, and pyramiding SB resistance QTL and morphological trait QTL is a potential approach in improving rice SB resistance.展开更多
The major QTL-qSB-9^Tq conferring partial resistance to rice (Oryza sativa L.) sheath blight (Rhizoctonia solani Kvhn) has been verified on chromosome 9 of the indica rice cultivar, Teqing. In this study, the pros...The major QTL-qSB-9^Tq conferring partial resistance to rice (Oryza sativa L.) sheath blight (Rhizoctonia solani Kvhn) has been verified on chromosome 9 of the indica rice cultivar, Teqing. In this study, the prospect of this QTL utilized in molecular breeding program of japonica rice for sheath blight resistance was investigated. Most of the japonica rice cultivars showed lower level of sheath blight resistance than the indica rice cultivars. At the corresponding site of qSB-9^Tq, nine typical japonica rice cultivars from different ecological regions or countries proved to possess the susceptible allele(s). Introgression of qSB-9^Tq into these cultivars enhanced their resistance level by decreasing sheath blight score of 1.0 (0.5-1.3), which indicated that qSB-9^Tq had a large potential in strengthening the resistance of japonica rice to sheath blight. The use of the three molecular markers, which were polymorphic between Teqing and many japonica rice cultivars, promotes the application of qSB-9^Tq in a concrete molecular breeding program.展开更多
It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identi...It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998 2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000 bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.展开更多
基金supported by a grant from the Double Thousand Plan of Jiangxi Province(No.jxsq2019101057)the National Natural Science Foundation of China(No.3196150349)to Haihui Fu and Xu Jie,respectively.
文摘OsPLS4 encodes aβ-ketoacyl carrier protein reductase(KAR).The role of OsPLS4 in rice sheath blight(Rhizoctonia solani)remains unclear.Our preliminary studies showed that premature leaf senescence mutants(pls4)were highly susceptive to sheath blight in the early stage of rice development.To explore the role of this gene in the development of rice sheath blight,the transcriptome profiles of the rice pls4 mutant and wild type were compared by RNA-seq.The results revealed 2,569 differentially expressed genes(DEGs).The down-regulated genes were significantly enriched in the defense response-related biological processes.These down-regulated genes included the chitinase genes and WRKY genes,which were significantly changed in pls4 mutants.Furthermore,467 genes induced significant alternative splicing(AS)events.Among them,intron retention(IR)affected gene expression levels and functions of the vitamin B6(VB6)metabolism pathway related to sheath blight.This result suggests that IR plays an important role in the sheath blight resistance of mutant pls4.Together,these results indicate that pls4 could be involved in the biological process of sheath blight via DEGs and the fine-tuning of IR.The present study provides a molecular basis for further investigation of the resistance of rice to sheath blight.
基金the National Natural Science Foundation of China (31070397)
文摘Sheath blight, a disease caused by the fungus Rhizoctonia solani Kuhn (anamorph), has been the most economically significant disease of rice. It was frequently reported that the disease was well-controlled in integrated rice-duck system without the employment of fungicides. However, the effecting factors behind this phenomenon were rarely reported. In this research, experiment was carried out between two treatments, rice combined with ducks (RD) and conventional rice field without ducks rearing (CK) in early season rice paddy, to investigate the variations of sclerotia in floodwater and on rice plant, microclimate 10 cm above the waterline in rice paddy and activity of protective enzymes in rice plants. The results showed that the floating sclerotia in floodwater in RD was 86-91% lower than that in CK, and adhering sclerotia in rice plant in RD was 67-78% lower than that in CK. The relative humidity tested significantly lower and light intensity tested significantly higher in RD. The temperature in the early rice growth stages in RD was slightly lower than that in CK, but it was significantly higher (32.3-36.5~C) in the middle stage rice growth stages. The polyphenoloxidase (PPO) activity in RD were lower than that in CK, but the enhanced activity of phenylalanine ammonia-lyase (PAL), peroxidase (POD) and Chitinase was observed in different stages of rice growth in RD, especially the Chitinase which showed higher activity in all investigating days.
基金co-financed by the grants from the National Basic Resea rch Program of China (2013GB127800)the National Natural Science Foundation of China (31271996)
文摘Eight compounds were isolated from the fermentation cultures of rice sheath blight pathogen Rhizoctonia solani Kuhn. They were identified as ergosterol (1), 6β-hydroxysitostenone (2), sitostenone (3), m-hydroxyphenylacetic acid (4), methyl m-hydroxyphenylacetate (5), m-hydroxymethylphenyl pentanoate (6), (Z)-3-methylpent-2-en-1,5-dioic acid (7) and 3-methoxyfuran-2-carboxylic acid (8) by means of physicochemical and spectroscopic analysis. Among them, 2, 3, 5-8 were isolated from R. solani for the first time. All the compounds were evaluated for their biological activities. 4-6 and 8 showed their inhibitory activities on the radical and germ elongation of rice seeds. 1,4 and 7 showed moderate antibacterial activity to some bacteria. 4, 7 and 8 exhibited weak inhibitory activities on spore germination of Magnaporthe oryzae. 8 showed moderate antioxidant activity with the 1,1-diphenyl-2-picryhydrazyl (DPPH) andβ-carotene-linoleic acid assays. This is the first time to reveal compounds 5, 6 and 8 from rice sheath blight pathogen R. solani to have in vitro phytotoxic activity.
基金supported by a ‘Special Fund for Agro-scientific Research in the Public Interest’ from the Ministry of Agriculture of China(Grant No.nyhyzx3-16)
文摘To construct the T-DNA insertional mutagenesis transformation system for rice sheath blight pathogen Rhizoctonia solani AG-1 IA,the virulent isolate GD118 of this pathogen was selected as an initial isolate for transformation.The conditions for transformation of isolate GD118 were optimized in five aspects,i.e.pre-induction time,co-culture time,acetosyringone(AS) concentration at the co-culture phase,co-culture temperature and pH value of induction solid medium(ISM) at the co-culture phase.Finally,a system of Agrobacterium tumefaciens-mediated transformation(ATMT) for R.solani AG-1 IA was established successfully.The optimal conditions for this ATMT system were as follows:the concentration of hygromycin B at 30 μg/mL for transformant screening,8 h of pre-induction,20 h of co-culture,200 μmol/L of AS in ISM,co-culture at 25 ℃ and pH 5.6 to 5.8 of ISM at the co-culture phase.The transformants still displayed high resistance to hygromycin B after subculture for five generations.A total of 10 randomly selected transformants were used for PCR verification using the specific primers designed for the hph gene,and the results revealed that an expected band of 500 bp was amplified from all of the 10 transformants.Moreover,PCR amplification for these 10 transformants was carried out using specific primers designed for the Vir gene of A.tumefaciens,with four strains of A.tumefaciens as positive controls for eliminating the false-positive caused by the contamination of A.tumefaciens.An expected band of 730 bp was amplified from the four strains of A.tumefaciens,whereas no corresponding DNA band could be amplified from the 10 transformants.The results of the two PCR amplifications clearly showed that T-DNA was indeed inserted into the genome of target isolate GD118.
文摘The transgenic rice, Zhongda 2, which was genetically modified from an indica rice line Zhuxian B by rice chitinase gene (RC24), had high resistance to rice sheath blight (Rhizoctonia solan!) in laboratory and a two-year field experiment. The pathogen could invade sheath of Zhongda 2 and induce symptoms of the disease. No difference was noted in time of penetration or incubation period between Zhongda 2 and non-transgenic rice control, Zhuxian B, but the hyphae lysate could be observed earlier than control. Its resistance expressed as to inhibit the growth of mycelium in host tissue. Fis from Zhongda 2(4) crossed with other five non-transgenic rice lines showed higher resistance than donor non-transgenic parents, but the resistance was different along with the different maternal parents.
文摘To establish a standard system for geneticstudies on sheath blight resistance, a field testwas conducted at the experimental farm ofYangzhou University to compare several pro-cedures for inoculating rice plants with R.solani Kuhn (RH9). The varieties used wereJasmine 85, Teqing (resistant or moderatelyresistant), and Lemont (susceptible). They
基金supported by the Major Program of Guangdong Basic and Applied Basic Research(Grant No.2019B030302006)the National Natural Science Foundation of China(Grant No.31801677)。
文摘Trehalose metabolism is related to the sclerotial development of Rhizoctonia solani AG-1 IA,the causal agent of rice sheath blight(RSB).Here,we further elucidated the functions of three genes Rstre,Rstps1 and Rstpp that encode three key enzymes trehalase(TRE),alpha,alpha-trehalosephosphate synthase(TPS1)and trehalose 6-phosphate phosphatase(TPP)in the sclerotial development of R.solani AG-1 IA.Due to the lack of a stable genetic transformation system for R.solani,the heterologous expression of these three genes in Pichia pastoris GS115 was performed.The results showed that reactive oxygen species(ROS)contents and enzyme activities in R.solani decreased significantly in the treatments of the fermentation broths of Rstps1 and Rstpp transformants,and that in the treatment of the fermentation broth of Rstre transformant visibly increased.Furthermore,the fermentation broths of the transformants of all the three genes were added to potato dextrose agar(PDA)medium for the cultivation of R.solani,as a result,the dry weight of sclerotia in each PDA plate containing the fermentation broths of Rstps1 and Rstpp transformants significantly increased compared with the control,and that of Rstre transformant obviously decreased.Finally,178 proteins were found to interact with RSTPS1,and 16 of them were associated with ROS.Taken together,the findings suggest that all these three genes related to trehalose metabolism play important roles in the sclerotial development of R.solani AG-1 IA,and can be used as new targets for the development of novel high-efficiency fungicides for the controlling of RSB.
文摘Antagonistic bacterial strain 91-b possessedstronger antagonistic ability against SHBinfection. The control effects of the bacterizationagainst SHB were 58.1% in greenhouse and 45.1%in paddy. The effect of antibiosis JK-91-b exudat-ed by strain 91-b was studied in the present re-search.Bacterial strain 91-b was inoculated into
文摘We have recently developed a systematic method for the study on the inheritance of resistance to sheath blight. The key of the system is an innovated method of inoculation and investigation along with the employment of the permanent population. This paper reported the procedure of the system and the result of its verification.
基金supported by the grant from the Technological Key Project of Ministry of Agriculture of China on New Transgenic Variety Breeding (Grant No. 2008ZX08001-02)
文摘Sheath blight (SB) caused by Rhizoctonia solani is one of the three major diseases of rice, and now has become the most severe disease causing rice yield loss in China. Breeding and use of varieties resistant to SB is crucial in controlling the disease, but the advances achieved have been limited due to the tack of highly SB-resistant rice germplasm. Genetic analysis revealed that the SB resistance in rice was a typical quantitative trait controlled by multi-genes. Although many QTLs conferring resistance to SB have been identified in recent years, most of the QTLs only showed small effects and few of them have been evaluated for utilization potential. Many R. solani-resistant resources have been found in wild rice species, microorganisms and other plant species. It is already known that the SB-resistance could be improved in transgenic rice plants by genetic transformation. This paper reviewed the genetic mapping of loci associated with resistance to rice SB, the evaluation of the potential of resistance QTLs, and the resistant resources found in various organisms besides rice. To develop SB-resistant rice varieties, it is important to develop and explore new resistant rice germplasms, fine map and evaluate resistance QTLs, and also to pay attention to various bio-resources showing resistance to R. solani.
基金Supported by National Torch Plan Project(2010GH020365)Jurong Authorized Invention Patent Achievement Transformation Project of Jiangsu Province (ZL201003)
文摘The control effects of six kinds of reagents against rice sheath blight were compared in the test. The results showed that 24% thifluzamide SC 300 mL/hm2 and 20% Jinggangmycin ~ prochloraz WP 750 g/hm2 had good control effect against rice sheath blight, and their control effects after spraying for 7 and 14 d were 72.16%, 77.91% and 66.52%, 71.08%, respectively. The control effects of both reagents were significantly better than other test reagents and control re- agent Jinggangmycin, and they had no adverse effect on growth and development of rice. Considering from the aspects of control effect and economy, 20% Jinggang- mycin ~ prochloraz WP was suggested to be used to control rice sheath blight, its recommended dosage was 600 -750 g/hm2, and the reagent volume was 750kg with coarse spraying.
基金supported by a grant from the National Natural Science Foundation of China (Grant No. 31470247)
文摘Rice sheath blight,caused by Rhizoctonia solani(Kühn),is a notorious soil-borne disease prevalent in many rice-growing regions.Although several sporadic studies of mycoviruses in R.solani AG-1 IA have been reported for single strain of R.solani AG-1 IA,there have been no reports describing the distribution and diversity of mycoviruses in natural populations.In this study,43 R.solani AG-1 IA strains collected from different locations in China were examined for the presence of ds RNA elements to confirm the presence of viral infections.Electrophoretypes showed that 16 of the 43 fungal strains(37.2%)contained ds RNAs that can be characterized as viruses.Furthermore,the species-specific reverse transcription PCR(RT-PCR)showed ds RNA bands with similar sizes do not always contain the same virus but exist as mixed mycoviral infections.Thus,our findings indicate mycoviruses infecting R.solani AG-1 IA in China are diverse,widespread and universal.
文摘Sheath blight of rice, caused by Rhizoctonia solani AG 1. 1a, has become the most important disease and caused serious yield losses in some major rice-growing regions in China in recent years. In the present study, field plot experiment was conducted to examine the relationships between disease intensity and inoculum density (ID), the seasonal disease epidemic dynamics, and yield reductions due to disease damages. Results from the experiment demonstrated that the areas under progress curves of disease severity and those of percent rice tillers diseased were positively and closely related to the relative initial ID of the pathogen. The inoculum density-disease (IDD) relationships were simulated and the impractical linear models were obtained. Both logistic and Gompertz functions could be used to simulate the disease progress dynamics in time, but the progress curves of the disease severity were modeled better by the Gompertz than by logistic function. However, the Richards function was found to be the best in simulating the disease progress curves when a most appropriate value was chosen for the shape parameter m by using the computer software Epitimulator. Sheath blight infection decreased rice yield very significantly and a yield reduction of 40% was recorded in rice crop with the highest inoculum density. Rice yield was linearly and negatively correlated with the disease severity and the percent tillers affected. The simulated models for all these relationships were computed through executing Epitimulator software and were presented in this paper.
基金funded by the National Key R&D Program(grant number No.2017YFD0200600)and the earmarked fund for CARS-12.
文摘Rice sheath blight pathogen,Rhizoctonia solani,produces numerous sclerotia to overwinter.As a rich source of nutrients in the soil,sclerotia may lead to the change of soil microbiota.For this purpose,we amended the sclerotia of R.solani in soil and analyzed the changes in bacterial microbiota within the soil at different time points.At the phyla level,Proteobacteria,Acidobacteria,Bacteroidetes,Actinobacteria,Chloroflexi and Firmicutes showed varied abundance in the amended soil samples compared to those in the control.An increased abundance of ammonia-oxidizing bacterium(AOB)Nitrosospira and Nitrite oxidizing bacteria(NOB)i.e.,Nitrospira was observed,where the latter is reportedly involved in the nitrifier denitrification.Moreover,Thiobacillus,Gemmatimonas,Anaeromyxobacter and Geobacter,the vital players in denitrification,N2O reduction and reductive nitrogen transformation,respectively,depicted enhanced abundance in R.solani sclerotia-amended samples.Furthermore,asymbiotic nitrogen-fixing bacteria,notably,Azotobacter as well as Microvirga and Phenylobacterium with nitrogen-fixing potential also enriched in the amended samples compared to the control.Plant growth promoting bacteria,such as Kribbella,Chitinophaga and Flavisolibacter also enriched in the sclerotia-amended soil.As per our knowledge,this study is of its kind where pathogenic fungal sclerotia activated microbes with a potential role in N transformation and provided clues about the ecological functions of R.solani sclerotia on the stimulation of bacterial genera involved in different processes of N-cycle within the soil in the absence of host plants.
基金Supported by National Science and Technology Projects (2012BAD19B03).
文摘[ Objective] The paper was to confirm the best application period and frequency of 75% trifloxystrobin ·tebuconazole WG against rice blast and rice sheath blight. [ Method] Influences of different dosages and different application periods of 75% trifloxystrobin · tebuconazole WG on control effects against rice blast and rice sheath blight, as well as their effects on rice yields were studied in the paper. [Result] The control effects of three different fungicides application treatments against rice sheath blight were 80.24%, 83.0% and 67.99%, and the control effects against rice blast were 56.4%, 49.11% and 61.1%, respective- ly. Advanced application of fungicide for two times had good prevention effect against rice sheath blight ; properly delayed application of fungicides for two times was conducive to improving the control effect against rice blast, and one time application of sufficient fungicide during middle booting stage had higher control effect than application for two times. Effective panicle number per unit area, total grain number, 1 000-grain weight and moisture content of various fungicide application treat- ments did not have significant difference with those of the treatments without fungicide application, but grain number per panicle in treatments applied with fungicide was higher than the treatment without application. [ Conclusion] 75% Trifloxystrobin ·tebuconazole WG has better control effect on rice blast and sheath blight, which helps to promote the formation of rice grain and increases yield significantly. The fungicide application against rice sheath blight should be appropriately ad- vanced, and application for one time against panicle blast after middle booting stage is helpful to improve the control effect.
文摘Rice sheath blight disease (ShB), caused by Rhizoctonia solani, gives rise to significant grain yield losses. The present study evaluated the efficacy of Integral, the commercial liquid formulation of Bacillus subtilis strain MBI 600, against rice ShB and for plant growth promotion. In greenhouse studies, four log concentrations of Integral (from 2.2×10^6 to 2.2×10^9 cfu/mL) were used as seed treatment (ST). After 25 d, seedlings were dipped (SD) into Integral prior to transplanting. At 30 d after transplanting (DAT), leaf sheaths were inoculated with immature sclerotia of the pathogen. At 45 DAT, a foliar spray (FS) with Integral was applied to some treatments. The fungicide control was 50% carbendazim at 1.0 g/L, and a nontreated control was also included. Overall, there were 10 treatments, each with five replications. ShB severity was rated at 52 DAT, and seedling height and number of tillers per plant were rated at 60 DAT. In 2009, two field trials evaluated Integral at 2.2×10^8 and 2.2×10^9 cfu/mL. Integral was applied as ST, and seedlings were produced in a nursery bed. After 32 d, seedlings were treated with Integral as SD and transplanted into 10 m^2 blocks. Foliar sprays were given at 45 and 60 DAT. There were seven treatments, each with eight replications arranged as a factorial randomized complete block design. At 20 DAT, the plots were broadcast inoculated with R. solani produced on rice grains. Seedling height before transplanting, ShB severity at 90 DAT, and grain yield at harvest were recorded. Integral at 2.2×10^9 cfu/mL provided significant increase of seedling heights over other treatments under greenhouse conditions. The Integral treatments of ST + SD + FS at 2.2×10^9 cfu/mL significantly suppressed ShB over other treatments. In field studies, Integral provided significant increase of seedling height in nursery, and number of tillers per plant, compared with the control. ShB severity was significantly suppressed with higher concentrations of Integral compared to lower concentrations. Grain yield were the highest at an Integral concentration of 2.2×10^9 cfu/mL. Overall, Integral significantly reduced ShB severity, enhanced seedling growth, number of tillers per plant and grain yield as ST + SD + FS at the concentration of 2.2×10^9 cfu/mL under the conditions evaluated.
基金partially supported by the Open Funding from State Key Laboratory for Biology of Plant Diseases and Insect Pests(Grant No.SKLOF201403)by the Natural Science Foundation of China(Grant Nos.31571748 and 31701057)the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK20171293 and BK20141291)
文摘Sheath blight(SB) caused by the soil borne pathogen Rhizoctonia solani is one of the most serious global rice diseases. Breeding resistant cultivar is the most economical and effective strategy to control the disease. However, no rice varieties are completely resistant to SB, and only a few reliable quantitative trait loci(QTLs) linked with SB resistance have been identified to date. In this study, we conducted a genome-wide association study(GWAS) of SB resistance using 299 varieties from the rice diversity panel 1(RDP1) that were genotyped using 44 000 high-density single nucleotide polymorphism(SNP) markers. Through artificial inoculation, we found that only 36.5% of the tested varieties displayed resistance or moderate resistance to SB. In particular, the aromatic and aus sub-populations displayed higher SB resistance than the tropical japonica(TRJ), indica and temperate japonica sub-populations. Seven varieties showed similar resistance levels to the resistant control YSBR1. GWAS identified at least 11 SNP loci significantly associated with SB resistance in the three independent trials, leading to the identification of two reliable QTLs, qSB-3 and qSB-6, on chromosomes 3 and 6. Using favorable alleles or haplotypes of significantly associated SNP loci, we estimated that both QTLs had obvious effects on reducing SB disease severity and can be used for enhancing SB resistance, especially in improving SB resistance of TRJ sub-population rice varieties. These results provided important information and genetic materials for developing SB resistant varieties through breeding.
基金supported by the Key Project of National Science foundation of Jiangsu Higher Education Institutions, China (Grant No. 14KJA210003)the National Transgenic Projects (Grant No. 2014ZX08001-003B)the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), China
文摘Rice resistance to sheath blight (SB) is controlled by polygenes or quantitative trait loci (QTLs) and affected by plant morphological traits, qSB-9^TQ and TAG1^TQ, which control SB resistance and tiller angle (TA), respectively, were employed to test whether the combination of the two genes will further improve rice SB resistance and reduce yield loss rather than only one of them or neither. Using two pairs of near isogenic lines (NILs), TAC1^TQ was confirmed to contribute to SB resistance. However, its effect was less considerable than that of qSB-9^TQ. Subsequently, the two genes were introduced into two commercial rice varieties to develop a series of NILs. The NILs carrying both TAG1^TQ and qSB-9^TQ showed more resistance than the NILs containing only one of them. Comparing the grain yield per plant (GYP) under the three different SB disease conditions, namely slight, moderate and severe conditions, NILs carrying both genes apparently lost lower GYP than the NILs without the two genes and the NILs carrying only TAC1^TQ. Under slight disease condition, no significant differences were found on morphology, development and GYP associated traits except for TA between the NILs carrying both genes and either of them, indicating that the two genes have no inferior effect on rice agronomic traits. Results indicated that mAC1^TQ and qSB-9^TQ have high breeding potential, and pyramiding SB resistance QTL and morphological trait QTL is a potential approach in improving rice SB resistance.
基金the National High Technology Research and Development Program of China (863 Program) (No. 2006AA10Z165, 2006AA10A103 and 2007AA10Z191)the Ministry of Agriculture of China (No. nyhyzx07-049)the 948 Program (No. 2006-G51).
文摘The major QTL-qSB-9^Tq conferring partial resistance to rice (Oryza sativa L.) sheath blight (Rhizoctonia solani Kvhn) has been verified on chromosome 9 of the indica rice cultivar, Teqing. In this study, the prospect of this QTL utilized in molecular breeding program of japonica rice for sheath blight resistance was investigated. Most of the japonica rice cultivars showed lower level of sheath blight resistance than the indica rice cultivars. At the corresponding site of qSB-9^Tq, nine typical japonica rice cultivars from different ecological regions or countries proved to possess the susceptible allele(s). Introgression of qSB-9^Tq into these cultivars enhanced their resistance level by decreasing sheath blight score of 1.0 (0.5-1.3), which indicated that qSB-9^Tq had a large potential in strengthening the resistance of japonica rice to sheath blight. The use of the three molecular markers, which were polymorphic between Teqing and many japonica rice cultivars, promotes the application of qSB-9^Tq in a concrete molecular breeding program.
基金the National Natural Science Foundation of China(30270891) National 863 Program(2002AA241261).
文摘It is necessary to understand the bacterial populations associated with rice so as to provide more information and natural resources for effective management of major diseases in rice. A survey on screening and identification of gram-positive bacteria was conducted during 1998 2004. Seven hundred and fifty-six rice samples were collected from Zhejiang, Jiangsu, Fujian and Yunnan Provinces, China. Over 1000 bacterial isolates were isolated and tested for colony morphology, pathogenicity, and some characteristics of bacteriology including Gram staining, fluorescent pigment on Kings medium B and microscopic observation for endospore. Together with five standard reference strains, 74 representative gram-positive bacterial isolates were confirmed by Biolog and gas chromatographic analysis of fatty acid methyl esters. Five bacterial species of Bacillus and other three genera were identified and isolates from Bacillus sublitis and Bacillus megaterium, exhibited the most effective inhibition against the pathogens of sheath blight and bakanae disease of rice. A few isolates from Bacillus pumilus and Bacillus megaterium showed weak virulent on rice together with some virulent isolates, risk should be considered when isolates from these species were screened for biocontrol agents.