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.

Identification of Pathogens on Dry Blight Disease in Leaf Tip of Red-fleshed Kiwifruit in Qiandongnan Prefecture

In order to reduce the harm of diseases in red-fleshed kiwifruit in Qiandongnan Prefecture and ensure product quality, a new disease in the producing areas were investigated, and pathogen identification were carried out. The pathogen was isolated from diseased leaves by a tissue separation method. DNA sequencing was performed by the sequence analysis of ribosomal rDNA-ITS(Internal transcribed spacer) region, and a molecular evolutionary tree was constructed by the MEGA 4.0 software. The pathogenic fungus was classified and identified by combining morphological observation finally. The results showed that the dry blight disease in leaf tip was a new disease, which was caused by Epicoccum sorghinum, and it had a serious damage to red-fleshed kiwifruit.

Efficacy of Some Botanical Extracts on the Control of Late Blight Disease in Experimental Potato Field

Late blight caused by Phytophthora infestans (Mont.) De Bary is the most devastating disease of potato. This study was carried out to evaluate the efficacy of ten botanical extracts against the late blight disease incidence and severity in experimental potato field at University of Rajshahi, Bangladesh during 2019-2020. Crude aqueous extract of leaves of Syzygium cumini, Psidium guajava, Eucalyptus globusus, Carica papaya and Lawsonia inermis;fruits of Terminalia bellirica, T. chebula and Piper nigrum;flower buds of Syzygium aromaticum and cloves of Allium sativum were used at 5% (w/v) concentration for evaluation. Out of ten botanicals, Syzygium cumini leaves extract was found most effective in controlling the late blight disease incidence and severity up to 66 DAS (days after sowing) and increased the potato yield by 71.29% compare to untreated control. The efficacy of Lawsonia inermis extract against late blight disease was found promising and increased the potato yield by 48.51%. Other four botanical extracts (Terminalia chebula, Piper nigrum, Syzygium aromaticum and Carica papaya) showed moderate efficacy against the incidence and severity of late blight disease, and increased 30% more potato yield compare to control. These results suggest that botanical extract of Syzygium cumini has a great potential as an alternative of chemical fungicides to control the late blight disease of potato in eco-friendly way.

Characterization and Pathogenicity of Pseudopestalotiopsis vietnamensis Causing Gray Blight of Wuyi Rock Tea(Camellia sinensis)in China and Specific Mechanisms of Disease Infection

Gray blight disease(GBD)causes significant losses in tea production in China.Although genes and biological processes involved in resistance to fungal disease in tea plants have been identified,specific mechanisms of the GBD infection process remain unknown.In this study,morphological and multi-gene(TEF-TUB-ITS)phylogenetic characteristics were used to identify isolate CLBB1 of Pseudopestalotiopsis vietnamensis.Pathogenicity tests confirmed that isolate CLBB1 from tea leaves caused GBD in the susceptible tea cultivar Wuyi Rock(Camellia sinensis var.sinensis cv.Shuixian).Spores began to germinate 24 h after infection(hai),and after 48 h,elongated fungal hyphae formed from a single conidium.Transcriptome analysis revealed that 482,517,and 369 genes were differentially expressed at 24,48,and 72 hai,respectively,in Wuyi Rock tea leaves.Isolate CLBB1 infection elicited phenotype-related responses and activated defense-related pathways,including plant–pathogen interaction,MAPK signaling,and plant hormone signal transduction,suggesting a possible mechanism underlying phenotype-based susceptibility to CLBB1.Thus,a new Ps.vietnamensis strain causing GBD in the tea cultivar‘Shuixian’was discovered in this study.Transcriptome analysis indicated that pathogen invasion activated chitin-related MAPK pathways and that tea plants required a hormone to restrict CLBB1.

Management of needle blight (Lophodermium pinastri) disease in Blue pine trees in Kashmir,India

Evaluation of various fungicides against needle blight disease of pine was carried out at Shed Kashmir University of Agriculture Sciences and Technology of Kashmir （India） during the year 2008 and 2009. Applica- tion of various fungicides were evaluated in vivo at dif- ferent concentrations. However in both, mist-chamber and poly-chamber, the Blue pine （Pinus wallichiana Jackson） seedlings treated with hexaconazole 5EC （@ 0.03 %） or carbendazim 50WP （@ 0.1%） depicted significantly less disease incidence and intensity. The seedlings treated with mancozeb 75WP （@ 0.3 %） and chlorothalonil 75WP （@ 0.3 %） exhibited less disease incidence and intensity. Increase in relative humidity from 60 to 100 % signifi- cantly enhanced needle blight disease incidence and intensity. In field trial the fungitoxicants used either as single spray or protectant followed by systemic fungitoxi- cant spray significantly reduced disease incidence in Blue pine compared to check. The mean disease incidence in fungitoxicant treated plants varied from 11.82 to 25.51% as compared to 36.03 % in control.

Antifungal Potential of Chenopodium album L. against Chickpea Blight

Chenopodium album L. （bathu） leaves and roots were selected to evaluate their antifungal potential against the Ascochyta rabiei responsible for chickpea blight that causes destructive yield losses. Methanolic extract of C. album leaves and roots was prepared and their various applied concentrations, viz., 1%, 2%, 3%, 4% and 5% were tested against A. rabiei. Leaf extracts were found more effective and showed significant antifungal activity over the root extracts. C. album leaf was found effective in screening bioassays, so this was subjected for fractional guided bioassays. Different various organic fractions of leaf extract were isolated, viz., n-hexane, chloroform, ethyl acetate and n-butanol. These isolated fractions were serially diluted to check their minimum inhibitory concentration （MIC） along with a synthetic fungicide （72% WP, Puslan）. The MIC of various concentrations from 500 mg/mL to 1.95 mg/mL was recorded after 24 h and 48 h intervals. Ethyl acetate and synthetic fungicides were found most effectual in retarding conidial germination with MIC of 1.95 mg/mL after 48 h incubation periods. Chloroform fraction also inhibited the fungal growth whereas n-hexane and n-butanol fraction were found to be ineffective.

Weedy red rice has novel sources of resistance to biotic stress

Weedy red rice(Oryza sativa;WRR),a close relative of cultivated rice,is a highly competitive weed that commonly infests rice fields and can also naturally interbreed with rice.Useful genes for biotic stress have been maintained in WRR and can be explored for breeding.Here we describe genetic and physiological traits of WRR that can be beneficial in preventing major rice diseases.Rice blast,caused by the hemibiotrophic fungal pathogen Magnaporthe oryzae,and sheath blight disease,caused by the necrotrophic pathogen Rhizoctonia solani,are the two most damaging biotic stresses of rice.Many major and minor resistance genes and QTL have been identified in cultivated and wild rice relatives.However,novel QTL were recently found in the two major U.S.biotypes of WRR,blackhull-awned(BH)and strawhullawnless(SH),suggesting that WRR has evolved novel genetic mechanisms to cope with these biotic stresses.Twenty-eight accessions of WRR(PI 653412–PI 653439)from the southern USA were characterized and placed in the National Small Grains Collection,and are available for identification of novel genetic factors to prevent biotic stress.

Crop Diversity for Ecological Disease Control in Potato and Maize

本文针对中国西南山区作物病害发病高峰与降雨高峰重叠难以防治的难点,进行了生态调控马铃薯与玉米种植结构避雨避病的试验。试验结果表明,时间上提前和推后马铃薯种植避开了降雨高峰,平均降低晚疫病病情指数44.3%。空间上行距拉宽株距缩小,通风透光减轻病害,套种玉米的大斑病平均降低病情指数为14.8%,小斑病平均降低22.5%。本试验的另一重要结果表明,通过调整马铃薯种植结构可以大幅度提高耕地产出率,马铃薯与玉米套种,提前和推后种植马铃薯分别提高土地利用率1.738-1.766。本文研究结果对作物病害的生态防治和增加粮食产量有重要现实意义。通过时空优化作物与环境的配置,合理利用农业生态结构,适应最佳生态环境,实现优质高产高效。

Dynamic and Coordinated Expression Changes of Rice Small RNAs in Response to Xanthomonas oryzae pv.oryzae

Endogenous small RNAs are newly identified players in plant immune responses, yet their roles in rice （Oryza sativa） responding to pathogens are still less understood, especially for pathogens that can cause severe yield losses. We examined the small RNA expression profiles of rice leaves at 2, 6, 12, and 24 hours post infection ofXanthomonas oryzae pv. oryzae （Xoo） virulent strain PXO99, the causal agent of rice bacterial blight disease. Dynamic expression changes of some miRNAs and trans-acting siRNAs were identified, together with a few novel miRNA targets, including an RLK gene targeted by osa-miR159a. 1. Coordinated expression changes were observed among some small RNAs in response to Xoo infection, with small RNAs exhibiting the same expression pattern tended to regulate genes in the same or related signaling pathways, including auxin and GA signaling pathways, nutrition and defense-related pathways. These findings reveal the dynamic and complex roles of small RNAs in rice-Xoo interactions, and identify new targets for regulating plant responses to Xoo.

Paladin, a tyrosine phosphatase-like protein, is required for XA21-mediated immunity in rice

XA21 encodes a rice immune receptor that confers robust resistance to most strains of the Gram-negative bacterium Xanthomonas oryzae pv.oryzae(Xoo).XA21-mediated immunity is triggered by recognition of a small protein called RaxX-sY(required for activation of XA21-mediated immunity X,tyrosine-sulfated)secreted by Xoo.To identify components regulating XA21-mediated immunity,we generated and screened a mutant population of fast-neutron-mutagenized rice expressing Ubi:Myc-XA21 for those susceptible to Xoo.Here,we report the characterization of one of these rice mutants,named sxi2(suppressor of XA21-mediated immunity-2).Whole-genome sequencing revealed that sxi2 carries a deletion of the PALADIN(PALD)gene encoding a protein with three putative protein tyrosine phosphatase-like domains(PTP-A,-B,and-C).Expression of PALD in the sxi2 genetic background was sufficient to complement the susceptible phenotype,which requires the catalytic cysteine of the PTP-A active site to restore resistance.PALD coimmunoprecipitated with the full-length XA21 protein,whose levels are positively regulated by the presence of the PALD transgene.Furthermore,we foundd that sxi2 retains many hallmarks of XA21-mediated immunity,similar to the wild type.These results reveal that PALD,a previously uncharacterized class of phosphatase,functions in rice innate immunity,and suggest that the conserved cysteine in the PTP-A domain of PALD is required for its immune function.