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Cytology and Breeding of Hexaploid Alfalfa. I. Stability of Chromosome Number 1
Author(s) -
Yen ShengTian,
Murphy R. P.
Publication year - 1979
Publication title -
crop science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.76
H-Index - 147
eISSN - 1435-0653
pISSN - 0011-183X
DOI - 10.2135/cropsci1979.0011183x001900030028x
Subject(s) - biology , cultivar , ploidy , population , chromosome number , hybrid , botany , chromosome , transplanting , horticulture , karyotype , sowing , genetics , demography , sociology , gene
Two hexaploid amphiploids (2n=6x=48), a naturally occurring hexaploid, and two hexaploid wild species of alfalfa ( Medicago spp.) were used in this study. The parents, F 1 hybrids, and a portion of their progenies were analyzed cytologically. Variation in somatic chromosome number was detected in most of the populations studied. Chromosome numbers varied from 2n=36 to 2n=51 with a mean of 46.7 ± 2.51 in the F 1 population, and from 2n=33 to 2n=51 (except for one with 2n=72) with a mean of 46.1 ± 2.34 in the selfed and crossed progenies derived from euplold F 1 plants (2n=48). The percentage of hexaploids was estimated at 64 in the F 1 population and 27 in the selfed and crossed progenies of the euploid F 1 plants. A wide range in plant vigor among individual plants was observed in the field nurseries about 2 months after transplanting. The overall mean vigor score (I lowest to l0 highest) was 5.9 for the progenies of hexaploid F 1 plants and 5.6 for the progemes of aneuploid F 1 plants. Both values were significantly lower than the mean vigor of the cultivated check cultivars (2n=‐4x=32). The frequency of plants with vigor of 7 (average of the check cultivars) or higher within the progenies of hexaploid and aneuploid F 1 plants was 38 and 28%, respectively. No apparent relationship was detected between vigor and the chromosome number of the plants. In the progenies of hexaploid F 1 plants, 33% of the plants with vigor of 7 or higher were hexaploids.