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Rust Resistance in Asparagus F1 Hybrid Populations. Dennis A. Johnson, Plant Pathologist, Washington State University. Richard N. Peaden, Research Agronomist, U.S. Department of Agriculture-ARS, Irrigated Agriculture Research and Extension Center, Prosser, WA 99350. Plant Dis. 77:1144-1148. Accepted for publication 28 June 1993. Copyright 1993 The American Phytopathological Society. DOI: 10.1094/PD-77-1144.

Rust severity was evaluated 3 yr in the field using the area under the disease progress curve (AUDPC) to classify rust resistance in 10 asparagus F1 hybrid populations derived from crosses among parents resistant, moderately resistant, and susceptible to Puccinia asparagi. The effect of genotype on rust severity was highly significant, and progeny were continuously distributed from low to high AUDPC in all 10 populations, indicating quantitative inheritance. The estimate of heritability using regression of offspring on the male parent was 55%. Highly resistant parents from the cultivars Jersey Giant and Jersey Titan had significantly greater specific combining abilities than parents from moderately resistant or susceptible cultivars. Progeny means were significantly skewed toward low AUDPC values, suggesting dominant resistance. Transgressive segregation for resistance was not observed in populations from highly resistant parents, but it was observed in some populations from moderately resistant parents.