Inheritance in seed size of alfalfa: Quantitative analysis and response to selection

Seed size in alfalfa (Medicago sativa L.) has been positively correlated with seedling vigour and early growth, but there were few published reports on inheritance or selection for this trait. The objective of this research was to estimate components of genetic variance for inheritance of alfalfa seed size and determine the most efficient selection method. Components of genetic variance were estimated on seed and pollen plants of 'BIC-7-WH' and their progeny arranged in a North Carolina Design II mating design under controlled environmental conditions. Three selection methods, differing in parental control and selection pressure, were used to determine selection response. The seed parent genotype had a major role in determining alfalfa seed size, but the genotype of the seed had no influence. For genetic studies, pollen and seed parent effects on seed size should be measured on seed harvested from progeny plants. Seed size was controlled by additive and non-additive components of genetic variance. Heritability for seed size was 41.3%. Selection for seed size was effective and a significant shift for larger and smaller seed was attained after one cycle of selection.