GENE ACTION OF BIOMASS PARTITIONING IN ALFALFA DURING THE SEEDLING YEAR

Abstract

The use of a harvest index to assess biomass partitioning in alfalfa (Medicago sativa L.) has been scarcely attempted. The objectives of this research were to determine the effect of locations on harvest index, and gene action of such index in alfalfa. Progenies from Mating Designs II, and plant diallels, all with fixed effects, were evaluated at Rosemount and Becker, Minnesota, USA. The experimental unit consisted of 12 plants separated 2.5 cm within a 30 cm row segment. Progenies were evaluated in August, September, and October for shoot yield; and only in October for fall dormancy, and for crown and root mean dry matter weight per plant. Shoot, crown, and root dry weights were used to calculate a harvest index as the ratio shoot/(shoot+crown+root), based on dry matter weight for each of three and total harvests. Total harvest index means varied from 0.56 to 0.63 and were affected by locations. Design II and diallel analyses suggested that additive and nonadditive effects were important for the total harvest index. Results indicate that selection for the seasonal harvest index should be effective at either location.