Growth, cold-hardiness, protein content, and digestibility of 70 Leucaena seedlots on three sites in Texas, USA

Seventy seedlots of Leucaena leucocephala, L. pallida, L. diversifolia, L. retusa, L. esculenta, L. confertifolia, L. greggii and L. pulverulenta and various hybrid combinations were examined for survival to freezing weather, biomass production, leaf protein content and in vitro dry matter digestibility in Texas. Three sites along a 600 km north-south transect were chosen to provide a wide range in exposure to freezing weather. The minimum temperature on the warmer Three Rivers site was −7 °C while the minimum temperatures on the colder Vernon site was −14 °C. At the Three Rivers site where −7 °C temperatures occurred and where forage production was a priority and some winter frost damage was not a problem, L. leucocephala K636 and hybrids containing L. diversifolia and L. pallida have the most promise. If total lack of damage to −7 °C is essential, species such as L. retusa, L. pulverulenta (seedlot 61, 62) and hybrids such as L. retusa × L. greggii (53) and L. retusa × L. pulverulenta (55) have the greatest potential. This study examined only one family from each of the cold-hardy species as a parent in the promising hybrids. As extensive intraspecific genetic variation is present within these leucaena species there is great potential to find hybrids with much better combinations of cold hardiness, forage production, leaf protein and dry matter digestibility. This revised version was published online in June 2006 with corrections to the Cover Date.