YIELD, PSYLLID RESISTANCE, AND PHENOLIC CONCENTRATION OF LEUCAENA IN 2 ENVIRONMENTS IN HAWAII

Interspecific hybridization in the genus Leucaena produces hybrid vigo r, resulting in highly adaptable varieties that expand the growth rang e of the genus. This study was conducted to test the total biomass (co mbined stem and forage fraction), total forage dry matter (DM) yield, psyllid (Heteropsylla cubana Crawford) damage, and phenolic concentrat ion of Leucaena F-1 hybrids in comparison with species-level selection s in two distinctly different environments. A total of 19 Leucaena spp . and hybrid selections were tested for 2 yr at the Waimanalo and Meal ani Research Stations in Hawaii. Thirteen species and hybrid selection s were replicated three times and included species selections from L. pallida Britton & Rose; L. leucocephala (Lam.) de Wit; L. diversifolia (Schlechtend.) Benth. (2n = 4x); and L. trichandra (Zucc.) Urban [syn . L. diversifolia (Schechtend.) Benth. subsp. trichandra (Urban) F.J. Pan] (2n = 2x). Additionally, five selections were interspecific F-1 h ybrids and two were advanced-generation interspecific hybrids. Six oth er selections were augmented in the trials. Over 2 yr, L. pallida x L. leucocephala F-1 hybrids (K748 x K636 and K748 x K584) had the highes t DM yield at both locations. At Waimanalo, K748 x K636 produced 53.4 Mg ha(-1) total DM biomass of which 24.6 Mg ha(-1) was forage, while a t Mealani, K748 x K636 produced 29.4 Mg ha(-1) total DM biomass and 9. 6 Mg ha(-1) forage. These yields were twice those of L. leucocephala a t Waimanalo and eight times greater at Mealani. Leucaena leucocephala was the most susceptible to psyllid damage (P < 0.001), while the most resistant was L. trichandra (2n = 2x). Leucaena pallida hybrids had i ntermediate levels of psyllid resistance. Psyllid damage was negativel y correlated with forage DM once at Waimanalo (r = -0.37, P < 0.05, n = 42). Forage phenolic concentration averaged 110 mg g(-1) for all tre atments at both locations and was correlated once to psyllid damage (r = 0.32, P < 0.05, n = 42) at Waimanalo. Superior yield, psyllid resis tance and cold tolerance of L. pallida x L. leucocephala hybrids was o bserved at low and high elevation sites.