The Effect of Potassium Phosphite in the Induction of Some Rice Resistance Genes in Following the Sheet Blight Disease Agent Rhizoctinia Solani

Rice (Oryza sativa L.) is one of the most important cereals which known to have high nutritional value in foods population worldwide. Rice sheath blight is considered as a critical diseases and Rhizoctonia solani (Teleomorph: Thanatephorus cucumeris) is the causal agent of the disease. Induction of resistance by chemical compounds is a very interesting alternative approach in plant disease management. Various biotic and abiotic factors have a role in activation of resistance genes expression in plants. Potassium phosphite is among the chemical compounds which is able to induce of resistance genes in plants and leads to suppression of diseases by directly affecting the pathogens and indirectly by stimulating the host defense responses. In this study, the effects of potassium phosphite application was considered on the expression of some pathogenesis related genes in both Tarom (Resistance) and Khazar (susceptible) cultivars in challenging with R. solani.

The factorial experiment completely randomized design was used in this research. The effect of Potassium phosphite on Tarom (Resistance) and Khazar (Sensitive) rice cultivars in challenging with R. solani was considered. Four weeks old rice treated with potassium phosphite and as well mock plants were infected with the disease causal agent, R. solani. The sampling carried out at 0, 24, 48, 72 and 96 hours after infection. After total RNA extraction and cDNA synthesis, real-time quantitative PCR was performed to studying the expression pattern of PAL, LOX, PR1, PR3 and PR5 genes using specific primers.

In this research, findings demonstrated that there is a significant increase in the expression of PAL, LOX, PR1, PR3 and PR5 genes in potassium phosphite treated rice when compared to the mock plants. The effects of the treatments in all traits in the expression level of LOX, PR1, PR3 and PR5 genes were significant, but in the expression level of the PAL gene, in the treatment-cultivar and treatment-cultivar-time traits were not significant. Nevertheless, for the other traits it was significant. Between the Tarom (Resistance) and Khazar (Susceptible) cultivars, except for the PR1 gene, there was a significant difference in the rest of mentioned genes. As well, between the treatments, all five genes had a significant mean comparison.

These findings show that potassium phosphite causes a rapid and intense response of the rice plant against R. solani through the induction of different genes and leads to increase in sheat blight disease resistance. Actually in Tarom cultivar, resistance genes were expressed faster and further than Khazar cultivar.