AN ANALYSIS OF OUTCROSSING IN CERTAIN COMPLEX-HETEROZYGOUS EUOENOTHERAS. I. FREQUENCY OF OUTCROSSING

Hoff , Victor J. (U. Arkansas, Fayetteville.) An analysis of outcrossing in certain complex-heterozygous Euoenotheras. I. Frequency of outcrossing. Amer. Jour. Bot. 49(7): 715–721. 1962.—Eleven complex-heterozygous races of Euoenothera were used for study. The races were grown in the midst of the experimental garden in which plants from approximately 150 races and hybrid combinations were growing together in close proximity so as to afford the maximum opportunity for outcrossing. Many capsules (126) resulting from unguarded flowers were collected from the chosen races and the seed grown to determine the number of hybrid plants resulting from outcrossing within each fruit. Among the various capsules, the number of outcrosses ranged from 0% to over 50% of the plants grown, while the total amount of outcrossing ranged from 0.7 to 7.8% among 5 different collections of capsules. A relationship between the amount of pollen produced by a flower or normally deposited on its stigma and the degree of outcrossing was noted. It is concluded that outcrossing probably occurs with sufficient frequency to account for the large number of complex-combinations found in nature.