Abstract

Intraspecific hybrids in Eragrostis curvula (Schrad.) Nees, an arid land grass common to southern Arizona, and their progeny families were used to study expression of mode of reproduction. The original cross involved sexual (2n=40) by apomictic (2n=40) parents, of widely differing phenotypes. Cytological determinations were associated with quantitative variation of the progeny. Data provided evidence for three genotypes for mode of reproduction in E. curvula. Minimum variability in height (C.V.=c. 5%) was shown in a family derived from the apomictic parents, with the parent and progeny of nearly identical heights. Considerable height variation (C.V.=c. 25%) was found in four F2 families of sexual origin, with distributions that were continuous within families, but with means different from that for the respective F1 plants. Bimodal progeny distribution was shown by a third genotype designated as facultative in mode of reproduction. Among the progeny from apomictic and sexual genotypes, the facultative genotype produced 75% uniform and 25% variable progeny, respectively. Facultative apomixis was confirmed in E. curvula by the relationship of the mean height of the uniform subpopulation to its parental height.