Reciprocal Differences in Bee‐Pollinated Alfalfa Strain Crosses as an Indicator of Crossing Patterns and Aids to Selection¹

Abstract

Strain crosses have shown potential as a method of incorporating multiple‐pest resistance into alfalfa (Medicago sativa L.) cultivars. Another application of strain crossing is to produce populations for further selection. Bee‐pollinated strain crosses increase the complexity of pollination patterns and decrease predictability as compared with hand‐pollinated strain crosses. This study was conducted to evaluate differences between reciprocal strain crosses as an indicator of percent crossing and to compare levels of resistance in reciprocal strain crosses with parental sources as an aid to selection. The parental sources and reciprocal strain crosses were evaluated for resistance to two diseases, one insect, forage yield, and fall dormancy. Approximately 90% of the reciprocals of strain crosses were significantly different for pest resistance and fall dormancy. This was attributed to crossing within parental sources. Level of pest resistance in reciprocals was approximately halfway between the midparent value and the parental source that would be expected if crossing between parental sources was 50%. This level of crossing between parental sources would significantly reduce the size of the required population for selection. Forage yields of reciprocal strain crosses were similar.