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Title: SOURCES OF RESISTANCE TO ANTHRACNOSE IN THE ANNUAL MEDICAGO CORE COLLECTION

Author
item Oneill, Nichole
item Bauchan, Gary

Submitted to: Plant Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/1998
Publication Date: N/A
Citation: N/A

Interpretive Summary: The annual Medicago species core collection consisting of 201 accessions representing 33 species was evaluated for resistance to anthracnose a major disease of alfalfa. A core collection is a small subset of the total collection which contains most of the variability which exists in the total collection. Evaluation of the core collection was conducted using standardized testing procedures in growth chambers. Most annual species and accessions were susceptible, and the degree of resistance found among accessions within species was highly variable. Only fourteen accessions from seven species exhibited resistance greater than 40%. These included accessions of M. murex, M. muricoleptis, M. polymorpha var. brevispina, M. polymorpha var. polymorpha, M. radiata, M. soleirolii, M. truncatula, and M. turbinata. Histological examinations of 14 of the most anthracnose-resistant accessions revealed that spores of the fungus germinated but failed to penetrate the leaf surface. The genetic variability of annual Medicago species offers the potential for locating and utilizing disease resistance genes through breeding or genetic engineering methods for the improvement of alfalfa. The identification of resistance to anthracnose in annual Medicago species will enhance the utilization of these species as a forage crop.

Technical Abstract: The annual Medicago core collection consisting of 201 accessions representing 33 species was evaluated for resistance to anthracnose caused by Colletotrichum trifolii. Evaluation of the core collection was conducted using standardized environmental conditions in growth chambers, and included M. sativa standard check cultivars Arc (resistant) and Saranac (susceptible). Most annual species and accessions were susceptible, and the degree of resistance found among accessions within species was highly variable. Only fourteen accessions from seven species exhibited resistance greater than 40%. These included accessions of M. murex, M. muricoleptis, M. polymorpha var. brevispina, M. polymorpha var. polymorpha, M. radiata, M. soleirolii, M. truncatula, and M. turbinata. Histological examinations of 14 of the most anthracnose-resistant accessions revealed that C. trifolii spores germinated and produced typical appressoria, but failed to penetrate and produce the primary and secondary hyphae characteristic of susceptible interactions. The genetic variability of annual Medicago spp. offers the potential for locating and utilizing disease resistance genes through breeding or genetic engineering methods. The identification of resistance to anthracnose in annual Medicago spp. will enhance the utilization of these species as a forage crop.