Diallel Analysis of Potato Leafhopper Resistance Among Selected Alfalfa Clones1

Abstract

The quantitative genetics of potato leafhopper Empoasca fabae (Harris) resistance among selected alfalfa (Medicago sativa L.) clones from three different alfalfa populations (Arc‐PLH1, B16 Syn.I‐PLH1, and Indiana Syn. C) was studied. Resistance was measured using no‐choice laboratory screening techniques. Feeding damage after 1 and 2 weeks of exposure to leafhopper adults (FD‐1 and FD‐2, respectively) and subsequent nymphal populations were measured. A 10‐parent diallel analysis was performed to detect combining ability effects for the resistance characteristics. General combining ability effects were significant for FD‐1 and the number of nymphs. Specific combining ability effects were significant for the number of nymphs. Midparent‐offspring regression analyses were performed to obtain narrow sense heritability estimates for the resistance characteristics. The estimates obtained were 0.31, 0.31, and 0.56 for FD‐1, FD‐2, and the number of nymphs, respectively. A positive phenotypic correlation was found between FD‐1 and FD‐2 (r = ‒0.73**) (**significant at the 0.01 level.). The number of nymphs was negatively correlated with high levels of FD‐I (r = ‐0.49**), but was not correlated with FD‐1 at low or moderate levels. Results indicate that further improvements in potato leafhopper resistance as measured by these characteristics can be made in populations derived from the selected alfalfa clones