Selection Within Wild Turkish Alfalfa Germplasm for Alfalfa Weevil (Coleoptera: Curculionidae) Resistance

Abstract

In 1981, alfalfa, Medicago sativa L., germplasm was collected in Central and Eastern Turkey to provide a new source to screen for alfalfa weevil, Hypera postica (Gyllenhal), resistance. This collection was evaluated at Beltsville in two stages, starting with primitive Turkish cultivars and concluding with wild alfalfas. Approximately 80,000 plants of the germplasm line B36 were screened as seedlings for resistance to neonate larvae, and 107 plants that were least defoliated by larval feeding were vegetatively increased and evaluated further for larval and adult feeding antixenosis. Five of the 107 selections demonstrated feeding antixenosis to larvae and/or adults and were significantly (P ≤ 0.05) less defoliated by feeding than ‘Ranger’ alfalfa. Larval and adult survival on the 107 clones did not differ significantly from that on ‘Ranger’. The five selections demonstrating feeding antixenosis were tested further for oviposition antixenosis. Oviposition was significantly less (P ≤ 0.05) on three of the five selections than on ‘Ranger’ when adults were confined on plants for 5 d. There was no significant correlation between stem diameter and oviposition rate, indicating that factors influencing oviposition antixenosis may be related to biochemical rather than morphological differences among alfalfa selections in this germplasm.