Genetic Resistance Mechanisms to Rhizoctonia Solani in Rice Systems

Rhizoctonia solani is a necrotrophic fungus responsible for sheath blight, one of the most destructive diseases of rice worldwide. Owing to the absence of complete resistance in existing cultivars, research has focused on dissecting polygenic resistance through quantitative trait loci (QTL) mapping, functional characterisation of candidate genes and targeted manipulation of defence pathways. Several classes of genes—including chitinases, cytochrome P450s, pathogenesis-related proteins and transcription factors—have been implicated in partial resistance. Advances in high-throughput genomics and transcriptomics have enabled the identification of resistance-associated loci and the elucidation of regulatory networks involving salicylic acid, jasmonic acid and ethylene signalling. Marker-assisted selection and gene pyramiding strategies have been deployed to combine favourable alleles from diverse germplasm. Concurrently, host-delivered RNA interference approaches have demonstrated the feasibility of silencing essential fungal pathogenicity genes in planta. Emerging biotechnological tools, such as genome editing and overexpression of broad-spectrum resistance genes, promise to accelerate the development of rice varieties with durable tolerance to R. solani while maintaining agronomic performance.

Research from Nature Portfolio

Recent studies have identified a rice cytochrome P450 gene, BSR2, whose overexpression confers broad resistance to multiple R. solani anastomosis groups in both Arabidopsis and rice. Transgenic lines displayed reduced lesion development and delayed symptom progression, albeit accompanied by slower growth and altered seed size, highlighting a trade-off between defence and development. Complementary work has employed host-delivered RNA interference to target two fungal MAP kinase homologues required for appressorium formation and invasive growth. Transgenic rice expressing hairpin constructs showed significantly lower expression of the targeted fungal genes upon infection and a marked reduction in pathogen biomass and disease severity. This approach represents a pioneering demonstration of durable, gene-specific fungal control without reliance on major resistance genes.

Genetic Resistance Mechanisms to Rhizoctonia Solani in Rice Systems publication trend

The graph below shows the total number of articles in genetic resistance mechanisms to rhizoctonia solani in rice systems across all publications each year (not limited to Nature Index journals).

Technical terms

Quantitative trait locus (QTL): A chromosomal region that contributes to variation in a quantitative trait, such as disease resistance, identified by statistical association between genetic markers and phenotype.

Anastomosis group: A classification of R. solani isolates based on hyphal fusion compatibility, reflecting genetic relatedness and host specificity.

Host-delivered RNA interference (HD-RNAi): A genetic engineering strategy in which plants express double-stranded RNA targeting essential pathogen genes, leading to their silencing during infection.

Cytochrome P450: A family of haem-containing enzymes involved in the biosynthesis of secondary metabolites and defence compounds, some of which confer resistance to fungal pathogens.

Marker-assisted selection (MAS): The use of DNA markers linked to desirable traits to accelerate breeding by selecting individuals carrying favourable alleles without phenotypic screening.

References

1. Rhizoctonia solani Kühn Pathophysiology: Status and Prospects of Sheath Blight Disease Management in Rice. Frontiers in Plant Science (2022).
2. OsWRKY80-OsWRKY4 Module as a Positive Regulatory Circuit in Rice Resistance Against Rhizoctonia solani. Rice (2016).
3. Comparative Transcriptome Analyses of Gene Expression Changes Triggered by Rhizoctonia solani AG1 IA Infection in Resistant and Susceptible Rice Varieties. Frontiers in Plant Science (2017).
4. Strategies to Manage Rice Sheath Blight: Lessons from Interactions between Rice and Rhizoctonia solani. Rice (2021).
5. Functional Characterization of Novel Chitinase Genes Present in the Sheath Blight Resistance QTL: qSBR11-1 in Rice Line Tetep. Frontiers in Plant Science (2016).
6. Novel Chitinase Gene LOC_Os11g47510 from Indica Rice Tetep Provides Enhanced Resistance against Sheath Blight Pathogen Rhizoctonia solani in Rice. Frontiers in Plant Science (2017).
7. Host Delivered RNAi, an efficient approach to increase rice resistance to sheath blight pathogen (Rhizoctonia solani). Scientific Reports (2017).
8. The rice CYP78A gene BSR2 confers resistance to Rhizoctonia solani and affects seed size and growth in Arabidopsis and rice. Scientific Reports (2019).