Comparative analysis of indices in the study of virulence diversity between and within populations of Puccinia recondita f. sp tritici in Israel

Isolates of Puccinia recondita f, sp, tritici (n = 260) obtained from bread , durum, and wild emmer wheat leaf collections throughout Israel during 199 3 to 1997 were analyzed for virulence on a set of wheat differentials. The overall frequency of virulence increased on differentials possessing resist ance genes Lr1, Lr2a, Lr3, and Lr26 and decreased on Lr17, Lr21, and Lr30. Genes Lr9 and Lr24 were resistant, while Lr18 was susceptible (98% in 1996) to all tested leaf rust isolates and Lr10 and Lr23 were susceptible to mor e than 78% of the isolates. Diversity between populations (years) was asses sed using Kosman's H-KB (based on degrees of similarity among distinct phen otypes) and H-KDis (based on frequencies of individual virulences) and Nei' s and Rogers' distances. The greatest difference occurred between the 1993 and 1994 populations. Phenotypic diversity within each population (year) wa s analyzed using the Shannon's, Simpson's, and Kosman's indices. The highes t diversity within years was recorded in 1994 and significantly increased f rom 1993 to 1994 for all indices. The variance in the diversity between pop ulations can be only partially explained by differences between correspondi ng diversities within population. The comparative analysis of diversity bet ween and within populations over the 5 years enabled a detailed study of ch anges in the pathogen population. The results show that the different measu res do not yield the same rank order of diversity.