Influence of Stem Diameter on Oviposition Preference of the Alfalfa Weevil and Its Importance in Breeding for Resistance¹

Abstract

This investigation consisted of two laboratory experiments which were designed to study the influence of stem size on oviposition preference of the alfalfa weevil, and the effect of that interrelationship on selection for resistant plants with large stems. F 1 , F 2 , and S 1 progenies were studied. Alfalfa strains and single crosses differed significantly for number of eggs per stem and stem diameter. In the two experiments the mean number of eggs per stem and stem diameter were correlated (r = .91**, 15 df and r .71**, 26 df). Plants with small stem diameters tended to have less oviposition. However, in progenies of several plants oviposition preference was not entirely dependent on stem diameter. Available evidence suggested that a breeding program, based on selecting plants with low oviposition preference and large stem diameter, might result in significant progress in developing an agronomically acceptable variety with resistance to oviposition. HOwever, this nonpreference type of resistance would have to be evaluated under field conditions before its potential economic value could be ascertained.