Key message RNAi mediated silencing of pectin degrading enzyme of R. solani gives a high level of resistance against sheath blight disease of rice. Abstract Rice sheath blight disease caused by Rhizoctonia solani Kuhn (telemorph; Thanatephorus cucumeris) is one of the most devastating fungal diseases which cause severe loss to rice grain production. In the absence of resistant cultivars, the disease is currently managed through fungicides which add to environmental pollution. To explore the potential of utilizing RNA interference (RNAi)-mediated resistance against sheath blight disease, we identified genes encoding proteins and enzymes involved in the RNAi pathway in this fungal pathogen. The RNAi target genes were deciphered by RNAseq analysis of a highly virulent strain of the R. solani grown in pectin medium. Additionally, pectin metabolism associated genes of R. solani were analyzed through transcriptome sequencing of infected rice tissues obtained from six diverse rice cultivars. One of the key candidate gene AG1IA_04727 encoding polygalacturonase (PG), which was observed to be significantly upregulated during infection, was targeted through RNAi to develop disease resistance. Stable expression of PG-RNAi construct in rice showed efficient silencing of AG1IA_04727 and suppression of sheath blight disease. This study highlights important information about the existence of RNAi machinery and key genes of R. solani which can be targeted through RNAi to develop pathogen-derived resistance, thus opening an alternative strategy for developing sheath blight-resistant rice cultivars.
In changing climatic conditions, heat stress caused by high temperature poses a serious threat to rice cultivation. A multiple organizational analysis at physiological, biochemical, and molecular levels is required to fully understand the impact of elevated temperature in rice. This study was aimed at deciphering the elevated temperature response in 11 popular and mega rice cultivars widely grown in India. Physiological and biochemical traits specifically membrane thermostability (MTS), antioxidants, and photosynthesis were studied at vegetative and reproductive phases, which were used to establish a correlation with grain yield under stress. Several useful traits in different genotypes were identified, which will be an important resource to develop high temperature-tolerant rice cultivars. Interestingly, Nagina22 emerged as the best performer in terms of yield as well as expression of physiological and biochemical traits at elevated temperature. It showed lesser relative injury, lesser reduction in chlorophyll content, increased super oxide dismutase, catalase and peroxidase activities, lesser reduction in net photosynthetic rate (PN), high transpiration rate (E), and other photosynthetic/fluorescence parameters contributing to least reduction in spikelet fertility and grain yield at elevated temperature. Furthermore, expression of 14 genes including heat shock transcription factors and heat shock proteins was analyzed in Nagina22 (tolerant) and Vandana (susceptible) at flowering phase, strengthening the fact that N22 performed better at molecular level also during elevated temperature. This study shows that elevated temperature response is complex and involves multiple biological processes that are needed to be characterized to address the challenges of extreme conditions of future climate.
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