Comparison of Selection Methods for Autotetraploids. II. Selection for Disease Resistance in Alfalfa¹

Abstract

One generation of selection based on selfed progeny test, selfed family, polycross progeny test, polycross family, and individual phenotype was conducted for resistance to Uromyces striatus Schroet. var. medicaginis (Pass.) Arth., Phoma herbarum West var. medicaginis Fckl., and Stem. phylium botryosum Wallr. in alfalfa ( Medicago sativa L.). Selected individuals from each method with each pathogen were intermated separately. The resulting populations were compared experimentally to evaluate relative effectiveness of the selection methods. Each method of selection produced a significant increase in resistance to U. striatus . Selfed progeny test and selfed family selection gave similar responses and were the most effective methods. Polycross progeny test and polycross family selection also gave similar responses, but were the least effective methods for U. striatus resistance. Response with individual selection was intermediate to responses with selfed and polycross methods. Each of the progeny test and family methods produced similar and significant increases in resistance to P. herbarum . Individual selection for resistance to P. herbarum was not effective. No method of selection produced a significant increase in resistance to S. botryosum