A PHYSIOLOGICAL GENETIC APPROACH FOR IMPROVING STRESS TOLERANCE IN PHASEOLUS VULGARIS L. VIA GENE TRANSFER FROM PHASEOLUS ACUTIFOLIUS A. GRAY (LECTIN, INTERSPECIFIC HYBRIDIZATION, INTROGRESSION, BACKCROSSING)
Abstract
Homozygous and heterozygous Phaseolus vulgaris and P. acutifolius parental genotypes were hybridized to determine if genotypic diversity would aid gene transfer between these species. Certain P. vulgaris female parents resulting from diverse intraspecific crosses increased the frequency at which species hybrids could be obtained through embryo culture of abortive embryos. Twenty backcross-1 (BC(,1)) lines (P. vulgaris = recurrent parent) were produced from 4 partially female-fertile hybrids, each of which had a heterozygous P. vulgaris female parent. Heterozygous P. acutifolius male parents did not influence the frequency at which interspecific hybrids could be produced but apparently improved their female-fertility. Fertility of the F(,1)BC(,1) generation was highly variable. The expression of tepary morphological (bract width) and physiological characters (apparent 30 kD seed polypeptide) was examined among BC(,1) individuals. The frequency of fertile individuals increased in each subsequent backcross generation (F(,1)BC(,2) and F(,1)BC(,3)). Many F(,2)BC(,2) individuals were more or less fertile than was their F(,1)BC(,2) parent. The expression of tepary characters, and their association with fertility in F(,2) and F(,3) BC(,2) populations was evaluated. Determination of the number of seed per pod and three morphological characters, bract width, primary leaf petiole length, and degree of cordation of the primary leaf were quantified. The expression of a tepary character was not associated with sterility per se. Field trials were conducted in southern Arizona from 1982 to 1985 to ascertain the stress tolerance of the parental species and BC(,2) lines. Individual plant selections were made in 1982 and 1983. In 1984, one twice selected backcross line displayed superior stress tolerance when compared to either of its original common bean parents (Sanilac, Puebla 152B1). Partial characterization of the 30 kD polypeptide marker was also performed. It was discovered to be a lectin and its potential as a chemical defense against bruchid beetle infestation was determined. Its amino terminus amino acid sequence has been determined to show a high degree of homology with common bean lectin sub-units.
Degree
Ph.D.
Subject Area
Genetics
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