P-314 - Begomovirus pathosystem component interactions, virus transmission, and virus population genetics are influenced by host resistance

Tomato yellow leaf curl virus (TYLCV) severely disrupts tomato production worldwide. TYLCV is a single stranded DNA virus (genus Begomovirus) and is transmitted by the sweetpotato whitefly (Bemisia tabaci). Host resistance is critical for virus management. Host resistance is conferred by (Ty_1-6) semi-dominant genes. Functionality of the genes varies from RNA-dependent RNA polymerase, leucine rich repeat, to mRNA surveillance factor (pelota), suggesting that resistance mechanisms could vary with genes. Gene expression patterns from tomato plants with individual Ty genes on the same genetic background are currently being annotated. Semi-dominant genes-conferred resistance is characterized by mild symptoms and reduced accumulation of TYLCV. Experiments indicated that TYLCV infection induced a subdued phenotype in resistant genotypes than the susceptible genotype. Also, TYLCV resistant genotypes accumulated less TYLCV loads than the susceptible genotype over different intervals. Overall, results suggested that TYLCV resistant genotypes would serve as less effective inoculum sources than the susceptible genotype. TYLCV whole genomes sequenced from resistant and susceptible genotypes in field collected samples did not indicate selection against resistance. Further, in the greenhouse, one susceptible and one resistant genotype were challenged with TYLCV for ten passages. Results indicated that there were more substitutions with time and in resistant than susceptible genotype genomes. However, there was no evidence of positive selection against Ty genes.