Comparative Embryo Sac Morphology at Anthesis of Cultivated and Wild Species of Arachis

Abstract

Introgression of germplasm from wild to cultivated species of Arachis is severely impeded because abortion processes often occur as a prepeg-, peg-(gynophore), or postpeg-elongation event. A comparative study of embryo sac morphology at anthesis was undertaken to determine if observable differences were present that could possibly explain abortion prior to peg tip swelling following soil penetration. Two wild Arachis species (A. duranensis and A. stenosperma) plus A. hypogaea cultivars NC 6 and Argentine were studied. Differences in starch grain concentration and cytoplasmic stranding organization were observed between A. hypogaea cultivars and the wild Arachis species. These differences probably have a significant impact on energy availability at syngamy and the subsequent early cell division of the embryo. An improper energy balance could contribute to the onset of abortion in interspecific hybrids. Modification in egg apparatus organization among all species was also observed which may account for low percentages of seed recovery resulting from interspecific hybridization attempts.