The reaction of tomato genotypes to whitefly-transmitted ToYVSV influenced by allelochemicals and the genes Mi, Ty-1, Ty-2, and Ty-3/Ty-4

Abstract

Forty-eight tomato genotypes, differing in their genotypic constitution (genes Ty and/or Mi + allelochemicals), were placed in a greenhouse with a high infestation of whiteflies, which had been previously fed with tomato plants infected by ToYVSV. The genotypes were kept in the same greenhouse throughout the entire experiment and were evaluated using a symptom rating scale. The estimated area under the disease progress curve (Area) and the mean scores from the last assessment were used to perform Dunnett's test with the susceptible and resistant controls. The genotypes were categorized according to their contents of acylsugar (AS) and zingiberene (ZB) and the presence or absence of the genes Mi, Ty-1, Ty-2, and Ty-3+Ty-4 to perform contrasts between groups and associate their effects to the different resistance levels observed. Alleles Mi and Ty-1 were more effective in promoting ToYVSV resistance in homozygozity than in heterozygosity. Lines homozygous for Ty-2 and Ty-3+Ty-4 showed significantly fewer symptoms than the resistant control, indicating that those alleles in homozygosity are the most effective in reducing ToYVSV symptoms. The results highlight the importance of pyramiding different resistance genes in adequate allelic dosages, in the process of lineages development aiming to obtain tomato genotypes with higher and more durable resistance to ToYVSV.