Inheritance of growth habit and quanititative characters in intervarietal crosses in Leucaena leucocephala (Lam.) de wit

Abstract

Five varieties of Leucaena leucocephala covering the range of variation in growth habit in this species were crossed in all combinations.

Measurements were made on leaf size, stem length, and flowering date on F₁ populations of seven crosses raised in a spaced-plant trial. Genotypic effects were significant for each character. Most of the F₁ means approximated to those of the higher parent. The asymmetrical distribution of the F₁ means about the mid-parent point indicated that there was some heterosis, in addition to additive effects.

Segregation ratios in F₂ and F₃ populations indicate that branching habit is controlled by two pairs of disomically inherited genes. One of these controls erect growth with lax branching v. bushy growth with denser branching. The other controls absence v. presence of strong basal branching.

Measurements of stem length and stem number were made on F₂ populations of several crosses. These characters appeared to be controlled by multiple genes affecting vegetative vigour. These genes are transmitted independently of the genes controlling branching habit.