Genetic control of development traits related to productivity of grain sorghum under various soil water supplies

Six inbred lines of grain sorghum (Sorghum bicolor L. Moench) were chosen on the basis of their diversity for several developmental and productivity traits. These parents (3 R-lines and 3 B-lines) were crossed in a complete diallel design (fixed model, without parents) in order to study the inheritance of the developmental and productivity traits. In addition, the 3 R-lines were crossed with 3 A-line counterparts to the B-lines for study of male sterile cytoplasm effects upon these traits. The crosses were performed in a greenhouse by the hand-emasculation method. The 39 F, progenies were grown in the field at Brownfield, Texas in a loamy-sand soil under 100% ETa and 50% Eta irrigation levels in 1985 and 1986. Measurements were conducted for developmental traits and productivity traits. From these measurements, several whole plant water use efficiency traits involving productivity per unit leaf area were calculated.

Considerable genetic variation was found for most developmental and productivity traits studied. For some traits, this genetic variation was consistent over irrigation regimes and years. However, for several traits this genetic variation differed among irrigation regimes and years. Most of the genetic variation was accounted for by additive genetic effects for most traits while some traits were also controlled by non-additive genetic effects and a few traits exhibited significant reciprocal and maternal effects. Thus most traits studied can be genetically improved in these lines through breeding although some will require careful choice of both parents in hybrid combinations and many may require selection to be conducted over several environments.

Seed number was found to be the predominant grain yield component. Grain yield was closely associated with total above-ground biomass suggesting genetic improvement of harvest index would be difficult. Leaf area was associated with grain yield suggesting that leaf area, rather than number of leaves, has the greater effect upon grain yield.