Development of HY1 hybrid embryos between a cultivar of Phaseolus vulgaris L. and a wild genotype of Phaseolus coccineus L.

Abstract

Reciprocal crosses between Phaseolus vulgaris and P. coccineus frequently lead to embryos abortion in all the developmental stages. However, the P. vulgaris NI637 cultivar and the wild form NI1108 of P. coccineus present abilities for combination. The abortion rate of pods is 93.93% when NI1108 is the maternal parent against 43.49% when it is the pollinator. The technique of histological resin sections of 2-Hydroxyethyl Methacrylate (HEMA) allows the analysis of the evolution of self-pollinated embryos and 3-14 days old hybrids after pollination. The growth rate does differ between the two types of embryos. On the basis of developmental stages, the form of embryo on one hand, and the ovary tissues on the other hand, present several specificities. The self-pollinated embryos regularly developed according to the initial polarity apex-base. In NI1108xNI637 hybrid embryos, the suspensor is hypertrophied over the embryo proper. These embryos of small size, present a slow growth compared to the self-pollinated ones and the NI637xNI1108 hybrids. These observations will allow the identification of the stages concerned by more abortions, explain their possible causes, and describe the expression of abortion symptoms in hybrid embryos during the embryogenesis within the Phaseolus genus, in view of improving the common bean production. Key words : Plant embryos, interspecific hybridization, abortion, suspensor