Diversity for virulence in a sexually reproducing population of Puccinia coronata

Abstract

Diversity for virulence in a sexually reproducing population of Puccinia coronata Cda. was studied among isolates collected at three distances from a buckthorn hedge at six sampling periods during the summer. Among 360 isolates, 155 distinct phenotypes were identified on 28 differential oat cultivars. About 60% of the phenotypes were represented by a single isolate. The number of phenotypes found decreased with time and distance from the hedge. Host responses were classified into low (0 and 0;), intermediate (1 and 2), and high (3 and 4) infection type classes. The Shannon–Wiener index of diversity decreased with distance from the buckthorn hedge from 2.58 at the 1-m site to 1.35 at the 10-m site and decreased with time from 3.42 in the second to 2.71 in the sixth sampling period. The mean number of virulence differences among phenotypes in each collection ranged from 4 to 12 with 28 hosts. Both distance and time contributed significantly to the decrease in Shannon–Wiener index and number of phenotypes in multiple regression analyses.