Genetic relationships of crown rust resistance, grain yield, test weight, and seed weight in oat

Integrating selection for agronomic performance and quantitative resistance to crown rust, caused by Puccinia coronata Corda var. avenae W.P. Fraser & Ledingham, in oat (Avena sativa L.) requires an understanding of their gen etic relationships. This study was conducted to investigate the genetic rel ationships of crown rust resistance, grain yield, test weight, and seed wei ght under both inoculated and fungicide-treated conditions. A Design If mat ing was performed between 10 oat lines with putative partial resistance to crown rust and nine lines with superior grain yield and grain quality poten tial. Progenies from this mating were evaluated in both crown rust-inoculat ed and fungicide-treated plots in four Iowa environments to estimate geneti c effects and phenotypic correlations between crown rust resistance and gra in yield, seed weight, and test weight under either infection or fungicide- treated conditions. Lines from a random-mated population derived from the s ame parents were evaluated in three Iowa environments to estimate heritabil ities of, and genetic correlations between, these traits. Resistance to cro wn rust, as measured by area under the disease progress curve (AUDPC), was highly heritable (H = 0.89 on an entry-mean basis), and was favorably corre lated with grain yield, seed weight, and test weight measured in crown rust in-oculated plots. AUDPC was unfavorably correlated or uncorrelated with gr ain yield, test weight, and seed weight measured in fungicide-treated plots . To improve simultaneously crown rust resistance, grain yield, and seed we ight under both lower and higher levels of crown rust infection, an optimum selection index can be developed with the genetic parameters estimated in this study.