Comparative study on the monocyclic components of plum rust with isolates from three growing regions in Brazil

Abstract

This study aimed to evaluate the effect of temperature and wetness period (WP) on urediniospore germination of Tranzschelia discolor and the influence of temperature in the latent period and the number of pustules/cm2 produced by isolates obtained from São Paulo (SP), Paraná (PR) and Santa Catarina (SC) states in Brazil. Spore germination was assessed under six temperatures (10–35°C) in combination with six WPs (3–48 hr). The latent period and the number of pustules were assessed in detached plum leaves inoculated with T. discolor at temperatures from 10 to 35ºC. In addition, the number of pustules produced by the three isolates was compared for 15 days at 23°C. The optimum temperatures for urediniospore germination estimated were 24.2, 24.4 and 24.3°C for isolates from PR, SC and SP, respectively, in the WP of 48 hr. The shortest latent periods estimated for PR, SC and SP isolates observed were 10.3, 8.9 and 10.6 days, at the optimal temperature of 21.9, 22.1 and 22.4°C, respectively. The greatest number of pustules/cm2 was 39.8, 158.5 and 63.1, for PR, SC and SP isolates, at the optimal temperature of 22.2, 22.2 and 22.7°C, respectively. Differences between isolates were observed for the latent period, which was shorter in leaves inoculated with the SC isolate. In addition, the number of pustules was greater in leaves inoculated with the SC isolate as compared to the latent periods and the number of pustules on leaves inoculated with the isolates from the other states. The highest rust progress rates were observed for isolates from the states of Santa Catarina and São Paulo. This information serves as a background study to better understand how plum leaf rust epidemics occur in the field under different environmental conditions, thus aiding in both the prevention of possible epidemics and the conception of more efficient control strategies.