VIEW ARTICLE

Genetics

A Growth Chamber Comparison of Traits of Aggressiveness in Sexual and Asexual Populations of Puccinia coronata. J. H. Oard, Former research assistant, Department of Plant Pathology, Iowa State University, Ames 50011; M. D. Simons, plant pathologist, U.S. Department of Agriculture, Agricultural Research Service, Department of Plant Pathology, Iowa State University, Ames 50011. Phytopathology 73:1226-1229. Accepted for publication 30 March 1983. This article is in the public domain and not copyrightable. It may be freely reprinted with customary crediting of the source. The American Phytopathological Society, 1983. DOI: 10.1094/Phyto-73-1226.

Uredial isolates of Puccinia coronata, derived from aecia on Rhamnus cathartica in Minnesota, were compared for several traits of aggressiveness with uredial isolates from southern Texas where the role of the alternate host is reduced or nonexistent. Mean values of most traits differed significantly within each population. Uredial dimensions and urediospore production exhibited significantly higher mean values in the sexual population from Minnesota than in the asexual population from Texas. Uredial latent period and time to formation of telia were also significantly shorter in the sexual population. In contrast, there were no significant differences between the sexual and asexual population in the amount of genotypic or phenotypic variation, suggesting that sexual reproduction conferred no advantage to the sexual population in producing a greater range of variability for traits of aggressiveness. Confidence limits (P=0.05) of broad-sense heritability estimates for all traits ranged from 18 to 96% in the asexual population and from 26 to 98% in the sexual population, but no significant difference in heritability was detected for any trait between the two populations.