Description
Crown rust (Puccinia coronata [Pers.] Cda.) is the most prevalent disease found on annual ryegrass (Lolium multiflorum L.) of the southeastern USA. Determination of crown rust resistance is difficult because of the erratic nature of infections at most locations. As crown rust is present at Gainesville, FL each year, a rust nursery was designed to evaluate rust resistance and susceptibility of annual ryegrass. Evaluation consists of periodic rust ratings of the seed crop and regrowth of part of each plot after cutting. Nursery results indicate the buildup of rust, including at the date of 90% heading (start of flowering), and rust on regrowth under high rust spore load for all ryegrass genotypes. A rust index based on rust ratings at the 90% heading date for two or more growing seasons is proposed to distinguish highly-resistant, resistant, susceptible and highlysusceptible ryegrass cultivars.
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Field Evaluation of Crown Rust in Annual Ryegrass Populations
Crown rust (Puccinia coronata [Pers.] Cda.) is the most prevalent disease found on annual ryegrass (Lolium multiflorum L.) of the southeastern USA. Determination of crown rust resistance is difficult because of the erratic nature of infections at most locations. As crown rust is present at Gainesville, FL each year, a rust nursery was designed to evaluate rust resistance and susceptibility of annual ryegrass. Evaluation consists of periodic rust ratings of the seed crop and regrowth of part of each plot after cutting. Nursery results indicate the buildup of rust, including at the date of 90% heading (start of flowering), and rust on regrowth under high rust spore load for all ryegrass genotypes. A rust index based on rust ratings at the 90% heading date for two or more growing seasons is proposed to distinguish highly-resistant, resistant, susceptible and highlysusceptible ryegrass cultivars.
