EVALUATION OF DESMODIUM SPECIES HYBRIDS FOR DRY-MATTER AND SEED YIELD

Carpon desmodium [Desmodium heterocarpon (L.) DC] is adapted to pastur e conditions in southern Florida, but the cultivar 'Florida' has recei ved only limited producer acceptance, possibly due to low seedling vig or and susceptibility to root-knot nematodes, Meloidogyne species, A b reeding program was initiated in 1983 to incorporate variability for t hese traits from plant introductions into selected lines which retain the desirable characteristics of the released cultivar. A group of F-4 and F-5 lines were developed with apparent improved root-knot nematod e resistance and stand persistence, based on greenhouse and field sele ction nursery results. These lines were evaluated for seed production, forage dry matter yield, and persistence in three field experiments a t Gainesville. Seed production was evaluated in Exp, 1 during 1991 and 1992. Dry matter yield and persistence were evaluated in two separate experiments, Exp. 2 conducted from 1991 to 1993, and Exp. 3 conducted from 1992 to 1994. Two lines were identified which were consistently superior to 'Florida' and the other breeding lines evaluated. Seed yie lds ranged from 10 to 400 kg ha(-1) in 1991. Dry matter yields in Exp, 2 ranged from 2410 to 3000 kg ha(-1) in 1991, 390 to 5630 kg ha(-1) i n 1992, and 0 to 3360 kg ha(-1) at midseason 1993, when the test was t erminated. Dry matter yields in Exp. 3 ranged from 4250 to 9190 kg ha( -1) in 1993, and 490 to 9920 kg ha(-1) in 1994. The two breeding lines also exhibited significantly greater persistence than 'Florida' into the third growing season of each test. Limited quantity of seed from t hese lines will be available for regional evaluation in 1996.