Pulses are an important source of protein and play a significant role in sustainable production. India is one of the leading pulse producing countries in the world. Among the biotic stresses, Rhizoctonia solani (teleomorph - Thanatephorus cucumeris) is a significant destructive soil-borne plant pathogen that causes severe losses. The pathogen has a long survival ability and can persist for up to a year in plant debris and soil. However, through sclerotia it can survived for up to 2 years under similar conditions. R. solani is internally and externally seed-borne. Infected seeds, plant debris and sclerotia serve as a source of primary inoculum for succeeding seasons. Basidiospores produced on diseased plant parts are responsible for secondary spread, in addition to spread through contact. The disease development is supported by humid and warm environments. A total 470 isolates for R. solani were obtained from diseased samples of pulse crops collected during a survey programme across 16 agroecological regions of India, covering 21 states and 72 districts using a stratified multistage sampling design. The disease incidence was varied ranging from 6.8 to 22.2%. The isolates were categorized into 49 groups based on morphological features. The isolates were characterised in to seven anastomosis groups (AGs) with the highest frequency in AG3 followed by AG2-3 and AG5. The molecular markers showed 99–100% polymorphism and clustered the isolates into 7 major groups at 35% genetic similarity and 95% of isolates shared a common grouping pattern. High genetic similarity of ITS gene sequences was observed among isolates of different AGs, isolated from various crops and regions. The groups generated through phylogenetic analysis of ITS did not correspond to the agroecological regions, states, or crops of origin. The isolates showed variability in virulence and the virulence did not show any definite correlations with AG, origin, host, and parts of the plant of the isolates. The isolates were clustered into 5 pathotypes. Highly sensitive conventional and real time PCR based technology has been developed to detect R. solani at 6 h and 24 h after artificial inoculation, both under field and in vitro conditions. The probes labeled with radioactive and FAM demonstrated sensitivity and specificity of the markers. Bio-agent based strategies were developed for the disease management. Integration of T. virens based formulations as soil treatment with PBP and seed treatment with Pusa 5SD (T. virens) + carboxin proved to be exceedingly effective in minimizing the incidence of disease and enhancing the germination of seeds, lengths of shoot and root and grain yield. The defence related genes were up-regulated in both the resistant and the susceptible varieties in the presence of T. virens and in combination of T. virens and R. solani. Thus, the expression of genes related to defence was up-regulated in T. virens treated plants.

Diversity, diagnostics, epidemiology and management of diseases in pulse crops caused by Rhizoctonia solani

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发表日期：

2025年6月10日

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S. C. Dubey

摘要

Pulses are an important source of protein and play a significant role in sustainable production. India is one of the leading pulse producing countries in the world. Among the biotic stresses, Rhizoctonia solani (teleomorph - Thanatephorus cucumeris) is a significant destructive soil-borne plant pathogen that causes severe losses. The pathogen has a long survival ability and can persist for up to a year in plant debris and soil. However, through sclerotia it can survived for up to 2 years under similar conditions. R. solani is internally and externally seed-borne. Infected seeds, plant debris and sclerotia serve as a source of primary inoculum for succeeding seasons. Basidiospores produced on diseased plant parts are responsible for secondary spread, in addition to spread through contact. The disease development is supported by humid and warm environments. A total 470 isolates for R. solani were obtained from diseased samples of pulse crops collected during a survey programme across 16 agroecological regions of India, covering 21 states and 72 districts using a stratified multistage sampling design. The disease incidence was varied ranging from 6.8 to 22.2%. The isolates were categorized into 49 groups based on morphological features. The isolates were characterised in to seven anastomosis groups (AGs) with the highest frequency in AG3 followed by AG2-3 and AG5. The molecular markers showed 99–100% polymorphism and clustered the isolates into 7 major groups at 35% genetic similarity and 95% of isolates shared a common grouping pattern. High genetic similarity of ITS gene sequences was observed among isolates of different AGs, isolated from various crops and regions. The groups generated through phylogenetic analysis of ITS did not correspond to the agroecological regions, states, or crops of origin. The isolates showed variability in virulence and the virulence did not show any definite correlations with AG, origin, host, and parts of the plant of the isolates. The isolates were clustered into 5 pathotypes. Highly sensitive conventional and real time PCR based technology has been developed to detect R. solani at 6 h and 24 h after artificial inoculation, both under field and in vitro conditions. The probes labeled with radioactive and FAM demonstrated sensitivity and specificity of the markers. Bio-agent based strategies were developed for the disease management. Integration of T. virens based formulations as soil treatment with PBP and seed treatment with Pusa 5SD (T. virens) + carboxin proved to be exceedingly effective in minimizing the incidence of disease and enhancing the germination of seeds, lengths of shoot and root and grain yield. The defence related genes were up-regulated in both the resistant and the susceptible varieties in the presence of T. virens and in combination of T. virens and R. solani. Thus, the expression of genes related to defence was up-regulated in T. virens treated plants.