Cytogenetic studies of common bean (Phaseolus vulgaris) and the scarlet runner bean (Phaseolus coccineus) /

Abstract

the chairman of his graduate committee, for his unusual ability to "Kai-chiau" (open the doors of thinking), and his patience as an educator. The author also expresses his thanks to Dr. Kenneth H. Quesenberry and his group of cytogenetic co-workers for the orientation and facilities generously provided. Thanks are extended to the faculty members, staff and all the graduate students of the Vegetable Crops Department for the good times experienced during the author's pursuit of knowledge at the University of Florida. Special thanks are extended to the Brazilian Ministry of Education and the Escola Superior de Agricultura de Lavras for financial support during the author's training.

Inheritance of stigma type in materials derived from hybridization of Phaseolus vulgaris L. and Phaseolus coccineus L

“…The nature of this sterility, which remained formidable through 2 cycles of bacTccrossing to vulgaris , is not well understood. However, the possibility is not excluded that sterility factors may be linked to an important block of coccineus stigma alleles within an inverted chromosome segment of the type observed in similar materials by Cheng (1979). This arrangement would serve to protect the linkage and would account for the lack of improvement in fertility with backcrossing.…”

“…Stebbins (1958) Contrary to the early reports of Karpechenko (1925) and Lamprecht (1941), there is now cytological evidence indicating that meiosis in P. vulgaris X coccineus hybrids does not follow a completely normal course. One pair of univalents is occasionally seen at metaphase I in the parental species, as well as in the hybrid, and a maximum of three pairs of univalents has been reported in F^hybrids (Marechal, 1971;Cheng, 1979). Also, the average number of chiasmata per bivalent is somewhat reduced, compared with the parental species.…”

“…Most interesting of all the recent cytological findings has been the observation of chromosome bridges at anaphase I and anaphase n in vulgaris X coccineus hybrids. According to Cheng (1979), at least two, large paracentric inversions exist in the Fm aterials studied by him, and these accounted for 20% to 40% of the observed F^pollen abortion. The remainder was attributed to genic unbalance in gametes.…”

“…Tlie latter condition results from heterozygosity in the interacting genes in the coccineus parent. Sterility in F^plants, as determined by pollen stainability , is in the range of 60% to 90% (Lamprecht, 1941;Smartt, 1970;Cheng, 1979).…”

“…At anaphase I and metaphase II, occasional cells are noted with 10 chromosomes at one pole and 12 at the other. The unequal distribution may be due to asynapsls, followed by the movement of both univalents to a common pole, but it is thought more likely that nondisjunction is involved (Cheng, 1979).…”