Effect of Morphological Traits on Sheath Blight Resistance in Rice

Sheath blight, caused by the Rhizoctonia solani Kuhn, is one of the most serious diseases of rice (Oryza sativa L.). The relationship between morphological traits and sheath blight resistance was investigated in 1999 and 2000 by using a segregant population consisting of 240 inbred recombination lines, derived from an elite combination of Zhenshan 97 X Minghui 63. Partial correlation analysis between phenotypic data (morphological characteristics and heading date (HD)) and sheath blight ratings (SBR) showed that only one trait, plant compactness, was significantly correlated with resistance to sheath blight in both 1999 and 2000, eight traits, such as plant height, heading date, and penultimate leaf angle, were significantly correlated with SBR in either of the two years, and the remaining 10 morphological traits were not consistently associated with SBR in the two years. A major quantitative trait locus (QTL) controlling plant compactness was found to be in the site on chromosome 9 adjacent to the region responsible for qSB9, a major QTLs conferring sheath blight resistance. One out of the three QTLs contributing to a penultimate leaf angle was mapped approximately on the same region as another sheath blight resistance QTL, qSB5, located on chromosome 5. Whereas, no QTLs underlying most other traits was detected on the chromosomal region correlated with sheath blight resistance QTL. The results in the present study suggested that the morphological traits were not the main factors responsible for the SBR separation among the recombinant inbred lines (RILs) population. Nevertheless, some morphological characteristics had some indirect influence on expression of sheath blight resistance genes through altering a microclimate on paddy field so as to influence the infection of the pathogen and development of the disease. An efficient approach in resistance breeding to sheath blight was recommended by pyramiding major QTLs for sheath blight resistance and selecting those morphological traits that favor resistance gene expression.

The Effect of Three New Fungicides against Rice Sheath Blight in Field Experiment

[Objective] The aim was to study the effect of three new fungicides against rice sheath blight in field experiment. [Methods] The experiment set up 7 treatments with three times of repetition and designed by random grouping. By using 5 sampling points in each plot, and investigating continuous 4 holes of each point, total plants, diseased plants and disease degrees were recorded. Then disease index and control efficiency were calculated, and variance analysis was carried out. [Results] 300 or 450 ml/hm^2 azoxystrobin ＋ difenoconazole 325 g/L SC had better control efficiency to rice sheath blight and had no phytotoxicity effect, we should use it at the initial disease stage and continuously spray 2-3 times. [Conclusion] The experiment provided a theoretical basis for controlling rice sheath blight using fungicides.

Research on the Pathogen of Rice Sheath Blight(Rhizoctonia solani Kühn)and Its Pathogenicity in Sichuan Regions

[ Objective] The paper was to study the cultural characteristic of the pathogen of Rice Sheath Blight （ Rhizoctonia solani Kuhn） and its pathogenicity in Sichuan regions. [ Method] The samples of rice sheath blight collected from six main rice planting areas in Sichuan regions were separated. The separated pathogen of rice sheath blight was cultured on PDA medium, and its cultural characteristic was recorded. Meanwhile, the pathogenicity of the obtained 23 strains was determined. [ Result] The growth rates among different strains had significant difference. According to the growth rate, only one strain belonged to medium strain（colony diameter： 40 mm≤（Ф≤60 mm）, the rest were all slow-type strains （colony diam- eter Ф〈40 mm）, and there was no strain with fast growth rate （colony diameter Ф 〉 60 mm）. Pathogenicity test showed that the pathogenicity among strains was significantly different, only one strain had strong pathogenicity, and the others all had moderate or weak pathogenicity. [ Conclu- sion] The study confirmed the basic biological characteristics of the pathogen of rice sheath blight in Sichuan region, which would provide theoretical basis for effective control of rice sheath blight in the region.

Mapping QTLs Associated with Sheath Blight Resistance Using Chromosome Segment Substitution Lines of Rice(Oryza sativa L.)

In this study, a population of 119 chromosome segment substitution lines （CSSLs） derived from backcross between indica 9311 and japonica Nipponbare was employed to map quantitative trait loci （QTL） associated with sheath blight resis-tance in rice with toothpick inoculation method. A total of three sheath blight resis-tance-associated QTLs （qsb8-1, qsb8-2 and qsb8-3） were identified, which were lo-cated on adjacent molecular markers RM3262, RM5485 and RM3496 of chromo-some 8; the genetic interval was 81.7cM-91.7cM, 91.7cM-108.1cM and 108.1cM-119.6cM, respectively. The additive effect of qsb8-2 was negative, indicating that sheath blight resistance of susceptible parent harboring qsb8-2 fragment was en-hanced; additive effects of qsb8-1 and qsb8-3 were positive, indicating that sheath blight resistance of susceptible parent harboring qsb8-1 and qsb8-3 fragments was reduced.

Control Efficacy of Validamycin A·(0.2 Billion Spores/ml) Paenibacillus polymyxa DN-1 3% AS for Rice Sheath Blight

With validamycin A.（0.2 billion spores/ml） Paenibacillus polymyxa DN-1 3% AS as the test agent, the effects of different dosage and different application time on the control efficacy for＇ rich sheath blight were investigated. The results of two- year test showed that when the application amount was in the range of 45-90 g.a.i/ hm^2, the field efficacy of validamycin A-（0.2 billion spores/ml） P. polymyxa DN-1 3% AS in the initial infection stage of rich sheath blight （Le., the diseased plant rate was below 5%） reached 80.38%-89.06%, and that in the peak infection stage （i.e., the diseased plant rate was higher than 10%） reached only 41.12%-53.26%. The field efficacy of validamycin A.（0.2 billion spores/ml） P. polymyxa DN-1 3% AS at the early onset of rich sheath blight was significantly better than that at the onset, so that the application time of validamycin A .（0.2 billion spores/ml） P. polymyxa DN-1 3% AS should be appropriately brought forward in the prevention and control of rice sheath blight.

Mapping of QTLs for Sheath Blight Resistance Using Recombinant Inbred Lines of Rice(Oryza sativa L.)

A recombinant inbred line （RIL） population composed of 157 lines derived from an inter-subspecific hybrid of Daguandao/IR28 by the single seed descent method was used as materials, and the quantitative trait loci （QTLs） coffering the resistance to sheath blight in the 157 RILs and the parents were detected using the toothpick inoculation method. The disease indexes of rice sheath blight in the two parents and 157 RILs were scored and the QTLs responsible for rice sheath blight resistance were detected accordingly by QTL Cartographer software. The results showed that a total of 4 QTLs （qsbl, qsb2, qsb5-1, qsb5-2） conferring sheath blight resistance were detected on chromosomes 1, 2 and 5, and their variance explained ranged from 10.41% to 36.92%. The additive effect of qsb5-1 was negative, indicat- ing that the QTLs derived from donor parent IR 28 could enhance the resistance to sheath blight. However, the additive effects of qsbl, qsb2 and qsb5-2 were positive, indicating that the QTLs derived from donor parent Daguandao weakened the resis- tance to sheath blight.

Occurrence Regulation and Control Measure Comparison of Rice Sheath Blight

Rice sheath blight is widely distributed throughout the world, it can cause damage on many kinds of crops. Pathogen characteristics, infection cycle, occurrence law, damage law and different control methods of rice sheath blight in China are summarized, which will provide foundation for further worldwide research on the disease.

Efficacy of Difenoconazole-azoxystrobin 32.5% SC in Treatment of Rice Sheath Blight and Its Application Technology

[Objective] The efficacy of difenoconazole-azoxystrobin 32.5% SC for rice sheath blight and its application technology were discussed in this research. [Method] Three surveys were carried out. There were 5 fixed test clumps in each plot. The number of total plants and disease plants and disease progression in each fixed clump were recorded. The correlation effectiveness was calculated based on the growth rate of disease index. Significance analysis was performed with Dun- can＇s new multiple range method （DMRT）. [Result] The difenoconazole-azoxystrobin 32.5% SC had a good efficacy for rice sheath blight, and its efficacy increased with the increase of dose. If sprayed according to the dose of 450 ml/hm2 5 days before the beginning of heading stage of rice, difenoconazole-azoxystrobin 32.5% SC would have better effects on controlling rice sheath blight with correlation effectiveness reaching up to 95.14%, which was 2.06% higher than that of control drug （trifloxys- trobin-tebuconazole 75% WG, 225 g/hm2）. [Conclusion] Treated with difenoconazole- azoxystrobin 32.5% SC with dose of 450 ml/hm2, rice would have green upper leaves and less yellow middle and lower leaves. Moreover, the yield was in- creased significantly. The difenoconazole-azoxystrobin 32.5% SC had good safety. Therefore, difenoconazole-azoxystrobin 32.5% SC had a good application prospect in production.

Prospect of the QTL-qSB-9^(Tq) utilized in molecular breeding program of japonica rice against sheath blight

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.

Effect of Nitrogen Regimes on Grain Yield,Nitrogen Utilization,Radiation Use Efficiency,and Sheath Blight Disease Intensity in Super Hybrid Rice

Poor nitrogen use efficiency in rice production is a critical issue in China. Site-specific N managements （SSNM） such as real-time N management （RTNM） and fixed-time adjustable-dose N management （FTNM） improve fertilizer-N use efficiency of irrigated rice. This study was aimed to compare the different nitrogen （N） rates and application methods （FFP, SSNM, and RTNM methods） under with- and without-fungicide application conditions on grain yield, yield components, solar radiation use efficiency （RUE）, agronomic-nitrogen use efficiency （AEN）, and sheath blight disease intensity. Field experiments were carried out at Liuyang County, Hunan Province, China, during 2006 and 2007. A super hybrid rice Liangyou 293 （LY293） was used as experimental material. The results showed that RTNM and SSNM have great potential for improving agronomic-nitrogen use efficiency without sacrificing the grain yield. There were significant differences in light interception rate, sheath blight disease incidence （DI） and the disease index （ShBI）, and total dry matter among the different nitrogen management methods. The radiation use efficiency was increased in a certain level of applied N. But, the harvest index （HI） decreased with the increase in applied N. There is a quadratic curve relationship between grain yield and applied N rates. With the same N fertilizer rate, different fertilizer-N application methods affected the RUE and grain yield. The fungicide application not only improved the canopy light interception rate, RUE, grain filling, and harvest index, but also reduced the degree of sheath blight disease. The treatment of RTNM under the SPAD threshold value 40 obtained the highest yield. While the treatment of SSNM led to the highest nitrogen agronomic efficiency and higher rice yield, and decreased the infestation of sheath blight disease dramatically as well. Nitrogen application regimes and diseases control in rice caused obvious effects on light interception rate, RUE, and HI. Optimal N rate is helpful to get higher light interception rate, RUE, and HI. Disease control with fungicide application decreased and delayed the negative effects of the high N on rice yield formation. SSNM and RTNM under the proper SPAD threshold value obtained high-yield with high efficiency and could alleviate environmental pollution in rice production.

Efficacy of Bacillus subtilis MBI 600 Against Sheath Blight Caused by Rhizoctonia solani and on Growth and Yield of Rice

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.

Influencing Factors on Rice Sheath Blight Epidemics in Integrated Rice-Duck System

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.

Analyses of the Temporal Development and Yield Losses due to Sheath Blight of Rice (Rhizoctonia solani AG1.1a)

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.

Advances in Mapping Loci Conferring Resistance to Rice Sheath Blight and Mining Rhizoctonia solani Resistant Resources

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.

Secondary metabolites of rice sheath blight pathogen Rhizoctonia solani Kühn and their biological activities

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.

Gram-Positive Bacteria Associated with Rice in China and Their Antagonists Against the Pathogens of Sheath Blight and Bakanae Disease in Rice

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.

Establishment of Agrobacterium tumefaciens-Mediated Transformation System for Rice Sheath Blight Pathogen Rhizoctonia solani AG-1 IA

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.

Characteristics of Resistance to Rice Sheath Blight of Zhongda 2,a Transgenic Rice Line as Modified by Gene “RC24”

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.

RAVL1 Activates IDD3 to Negatively Regulate Rice Resistance to Sheath Blight Disease

Sheath blight disease (ShB) has a severe impact on the production of rice. ABI3/VP1-like 1(RAVL1) negatively regulated the rice defense mechanism against ShB, however, this regulatorymechanism is not clearly understood. In this study, we identified that indeterminate domain 3 (IDD3) waspositively regulated by RAVL1. Further, chromatin immunoprecipitation (ChIP) assay, yeast one-hybridassay and transient expression assay indicated a direct binding between RAVL1 and the IDD3 promoterregion. IDD3 was ubiquitously expressed in different tissues and at different stages, and its expressionwas significantly enhanced by Rhizoctonia solani infection. IDD3 exhibited transcription activation activityin yeast and IDD3-GFP was found to be localized in the nucleus. IDD3 mutants exhibited no significantdifferences in response to ShB, while IDD3 overexpressors were more susceptible to ShB compared withwild type (WT) plants. Furthermore, IDD3 repressors were less susceptible to R. solani than WT plants.Interestingly, the expression of brassinosteroid-related genes (D2, D11 and BRI1) was lower in IDD3repressors and higher in IDD3 overexpressors compared with WT. However, the ChIP assay revealedthat IDD3 did not directly bind to the D2 and D11 promoters. Overexpression of IDD3 in BRI1 mutantd61-1 inhibited the activity of IDD3, reducing its susceptibility to ShB compared with IDD3 overexpressorand WT plants, indicating that IDD3 negatively regulated the rice defense mechanism against ShB by activatingthe BR signaling pathway. Thus, our analyses provided information to enhance the understanding of therice defense mechanism against ShB.

Control Effects of Jinggangmycin and Its Compounded Reagents against Rice Sheath Blight

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.