Alfalfa resistance to post-harvest Aspergillus species: Response to selection

Abstract

Alfalfa (Medicago sativa L.) cultivar development programs routinely incorporate resistance to fungal diseases that limit forage yield, quality and stand longevity. "Hay molding", caused by saprophytic fungi, reduces forage quality during the post-harvest period, but genetic resistance has not been reported. The objective was to determine the response to selection for post-harvest fungal resistance in alfalfa. Initially, 1144 genotypes from 22 alfalfa cultivars were screened for post-harvest fungal resistance with a combination of Aspergillus species. Forty resistant and 40 susceptible genotypes were selected by measuring percentage of leaf area with fungal coverage. The selected genotypes and their maternally derived half-sib families were screened for resistance to Aspergillus repens. Mean leaf area with fungal coverage was significantly (P < 0.05) lower for resistant than susceptible parental genotypes and maternal half-sib families. Percent leaf area with fungal coverage ranged from 13.2 to 70.5% (mean, 41.7 ± 1.7) among resistant and 28.2 – 83.4% (mean, 50.2 ± 1.7) among susceptible parental genotypes. Among the maternal half-sib families, resistant families ranged from 14.0 to 51.3% (mean, 32.1 ± 1.8) and susceptible families from 18.8 to 60.1% (mean, 40.3 ± 1.9). These results show a positive response to selection for post-harvest fungal resistance in alfalfa. Key words: Alfalfa, Medicago sativa, post-harvest fungi, Aspergillus species, breeding, divergent selection