Abstract
This study investigated the colonisation dynamics of wheat plants by Rhopalosiphum padi L. and Barley Yellow Dwarf Virus (BYDV), considering air temperature and host plant genetic resistance as key factors. Bioassays were conducted at different temperatures (5 to 35°C) with two wheat genotypes, partially resistant (BRS Timbaúva) and susceptible (Embrapa 16) to R. padi. Aphid dispersal was assessed every two days, cumulative thermal sum was estimated, and the proportion of plants with R. padi colonies was recorded. After 15 and 30 days, the total aphid population and its age structure on each plant were determined, as well as the viral titres of BYDV-PAV (ELISA). Generalised linear models were used to analyse of colonization data. The optimal temperatures were more explored with a logistic growth model analysis. The effect of genetic resistance was temperature-dependent; at 25°C, R. padi colonised Embrapa 16 more rapidly than BRS Timbaúva. Plant seropositivity differed significantly at the end of the experiment, with a higher percentage of seropositive plants for BRS Timbaúva, especially at temperatures optimal for R. padi development. These results were used to estimate the relationship between aphid populations and indirect damage derived from BYDV transmission, crucial for proper pest management and forming the basis for models estimating aphid focus progression, BYDV dissemination, and grain yield reduction.