Meiosis and fertility of interspecific hybrids betweenPhaseolus vulgaris L. andP. acutifolius A. Gray

Summary Meiosis and fertility of interspecific hybrids obtained from reciprocal crosses between Phaseolus vulgaris and P. acutifolius were examined. Bivalents as well as univalents were found at Metaphase I. The majority of the microsporocytes had four or more univalents and the average was 6.3 univalents per cell. The average number of lagging chromosomes at Anaphase I was 2.3 per cell and the most frequent chromosome distribution at late Anaphase I was 10–12. The lower than expected number of lagging chromosomes as compared with the number of univalents at Metaphase I suggests the possible occurrence of precocious separation of bivalents. The male fertility as measured by pollen stainability was 17%, however, the frequency of pollen germination in selfing was 3.5%. Upon selfing of the interspecific hybrids, no dividing embryos were found even though 7 and 26% of the ovules were fertilized at 12 hours and four days after pollination. In backcrosses to P. vulgaris (male), 6 and 20% of the ovules were fertilized and 0 and 4% of the ovules contained dividing embryos at the same sampling times. When P. acutifolius was the male parent, respective values were 8 and 31% for fertilization and 0 and 13% for ovules with dividing embryos. The frequencies of backcross embryos recovered at 14–26 days were in agreement with the frequencies of dividing embryos at four days. The ability to obtain backcross plantlets demonstrates the feasibility to further utilize interspecific hybrids for the improvement of P. vulgaris Technical paper No. 5311 of the Oregon Agricultural Experiment Station. Research was supported by the Oregon Agricultural Experiment Station, the Science and Education Administration of the U.S. Department of Agriculture under Grant 5901-0410-8-0028-0 from the Competitive Research Grants Office, the Research Council of Oregon State University (NIH Biomedical Research Support Grant RR 07079) and the Processor Research Council of Oregon, A.R. and C T.S. are respectively supported by an African Graduate Fellowship from the African-American Institute and a fellowship from the National Science Council of the Republic of China