Elicitation of defense responses in rice against sheath blight using salicylic acid and methyl jasmonate

Salicylic acid (SA) and methyl jasmonate (MeJA ) are plant defense elicitors with proven antimicrobial properties against various plant pathogens. Rhizoctonia solani, the pathogen responsible for rice sheath blight remains a significant challenge to rice production due to the lack of stable genetic resistance and the limitations of chemical fungicides. This study evaluated the potential of SA and MeJA as sustainable alternatives for sheath blight management in two contrasting rice genotypes, Tapaswini and CR Dhan 1014. Treatments included seed priming and foliar applications of SA and MeJA, with effects on growth, disease suppression, and yield were assessed. In vitro assays revealed that both SA and MeJA completely inhibited R. solani mycelial growth. SA also completely inhibited sclerotial formation at concentrations of 25, 50, and 100 mg, while MeJA achieved complete inhibition at 100 mg. For seedling traits, MeJA (100 mg) significantly enhanced germination in Tapaswini (95.00%), whereas SA (100 mg) was most effective for CR Dhan 1014 (94.67%). Both elicitors promoted shoot length and seedling vigor, with MeJA (100 mg) showing consistent positive effects across both genotypes. Combined seed treatment and foliar spray of SA (100 mg) reduced disease incidence significantly by 46.81% in Tapaswini and 33.33% in CR Dhan 1014 and inhibited vertical disease spread, with lower area under the disease progress curve (AUDPC). This treatment also enhanced the activity of defense-related enzymes, including phenylalanine ammonia-lyase (PAL), peroxidase (POD), and chitinase in both genotypes. These results highlight the dual role of SA and MeJA in promoting plant growth and inducing systemic resistance, supporting their potential as eco-friendly options for managing rice sheath blight.