Variability for Seed Size and Yield in Two Tall Dropseed Populations

Abstract

Tall dropsecd [Sporobofusclsper(Michx.) Kunth var. asper] is a drought-tolerant, perennial, warm-season grass that has potential for forage and soil conservation purposes. A prairie and an adjacent roadside population from northeastern South Dakota were evaluated for seed yield and size characteristics for 3 years (1985-1987) in a spacoplant nursery at Brookings, S.Dak. The objective was to obtain information on between and within population variability and intraphmt variability that would provide a basis for designing a breeding program to improve seed production and quality in this germplasm. The roadside population produced significantly (PCO.01) higher seed yields and larger mean 100~seed weight than the prairie population. Percent small seed (based on screen-separation of seed yields of individual plants into small, medium, and large seed size classes) decreased significantly (p<O.Ol) as seed yield increased, but the volume of small seed increased concurrently with seed yield. Percent large seed increased significantly (P<O.Ol) with increased seed yield and mean seed size. Highly significant (P-CO.01) differences were found among years for seed yield and mean seed size, but all plants produced seeds of each size class each year. Interand intrapopulation genetic variability was indicated for yield of the large seed size class. Screen-separation of individual plant seed yields could be used to identify superior genotypes to be used in the development of a cultivrr that produces a high percentage of large seed.