Inheritance of Pubescence in Selected Clones from Two Alfalfa Populations and Relationship to Potato Leafhopper Resistance1

Abstract

Intraspecific variation for pubescence occurs in many plant species and has been shown to be associated with insect resistance. The combining ability and heritability of pubescence and its relationship with resistance to the potato leafhopper, Empoasca fabae (Harris), was investigated in progeny from a fixed set of clones in two alfalfa (Medicago sativa L.) populations. The parental material included six clones each from ‘Arc’ and B16 (a synthetic involving two ‘Hairy Peruvian’ plant introductions). All plant material was grown in the greenhouse and resistance was measured using no‐choice laboratory screening techniques. The B16 parent‐clone population means were significantly greater than those for Arc for stem pubescence and lower for number of nymphs and feeding damage. Stem pubescence for the B16 crosses was significantly greater than for the Arc or Arc ✕ B16 crosses. Diallel analyses were performed to detect combining ability effects for density of simple hairs on stems and leaves. General and specific combining ability effects were highly significant for stem and leaf pubescence in all crosses with the exception of a non‐significant specific combining ability effect for stem pubescence in the Arc crosses. Heritability estimates indicated that the density of stem and leaf pubescence can be increased with selection in populations derived from the B16 selected parents. Heritability estimates were nonsignificant for stem and very low (0.28, P<0.05) for leaf pubescence in Arc. Significant negative correlations for all crosses and clones were found between stem pubescence, and both potato leafhopper feeding damage and nymphal populations.