Study of gene expression profiling of phenylalanine ammonia-lyase and thaumatin-like protein in sunflower infected by Sclerotinia stem rot disease

Sclerotinia stem rot disease caused by Sclerotinia sclerotiorum is one of the most important diseases of sunflower. The use of resistant genotypes is potentially an economically useful method for its control. In this study, the expression level of the genes encoding phenylalanine ammonia-lyase 2 (PAL2) and thaumatin-like protein (TLP) were measured in the LC106-C and RHA265 genotypes of sunflower inoculated with SSU53 isolate of S. sclerotiorum by real time PCR technique. The results revealed that transcript levels of both the PAL2 and TLP genes were significantly affected by genotype, time after inoculation and genotype-time of inoculation interactions. In particular there were significant differences between the expression of PAL in two genotypes 6 and 48 hours after infection. Concerning the expression of the TLP gene, the maximum difference between two genotypes was observed 48 hours after infection. The high expression level of studied genes in a resistant line compared to a susceptible one confirms the involvement of these genes in partial resistance of sunflower to Sclerotinia stem rot disease. It also confirms the resistance of LC106-C to the disease at the molecular level. The findings of this study can be useful in sunflower breeding programs for producing cultivars resistant to Sclerotinia stem rot disease.