Study of the early abortion in reciprocal crosses between Phaseolus vulgaris L. and Phaseolus polyanthus Greenm

The causes of early embryo abortion in the reciprocal crosses between Phaseolus vulgaris L. and Phaseolus polyanthus Greenm. were studied. Methacrylate resin sections, 2 micron meter thick, of 2 to 6 day-old hybrid seeds were used to examine the stage of embryo development and the state of seed tissues. These observations permitted the determination of the main causes of abortion and the developmental stages at which interspecific embryos should be rescued. Early nutritional barriers in Phaseolus polyanthus (Q) x Phaseolus vulgaris crosses are related to a deficient endosperm development while in reciprocal crosses, endothelium proliferation and, in some extent, hypertrophy of the vascular elements might be the main causes of early embryo abortion. The importance of the abnormalities observed during embryo development depended to a great extent on the compatibility between the genotypes crossed. Results also suggest that the appropriate time for embryo rescue when Phaseolus polyanthus is a female partner is at the early globular stage.