Genetic Variability for Root Characters in Alfalfa Populations Differing in Winterhardiness
1984
Pederson, G. A. | Hill, R. R. | Kendall, W. A.
A sample of plants from each of six alfalfa (Medicago sativa L.) cultivars with different levels of winterhardiness were used as parents in an experiment to obtain information on genetic variability for shoot dry weight, root diameter, number of lateral roots, root branching, and root dry weight. Cultivar intracrosses (from intercrossing plants within each cultivar) and intercrosses (from crossing plants in each cultivar with plants from the other five cultivars) were included in the experiment and analyzed as if the entries were in a diallel cross. Intercross and intracross progenies were evaluated in gravel culture tanks in the greenhouse and for two seedling years in the field. In the field experiment, intracross means were significantly greater than cultivar intercross means for root dry weight, root diameter at the crown, root diameter at 15 cm, and shoot dry weight. Intercross and intracross means did not differ significantly for number of lateral roots or for tap root branching. Cultivar intracrosses differed significantly only for number of lateral roots. General combining ability effects were significant for each of the traits measured in the field, but genotype ✕ year interactions were also very large. Correlations between field and greenhouse measurements of root traits were generally small and nonsignificant. Differences among cultivar intracrosses were significant for each trait measured in the greenhouse, but significant combining ability effects were detected only for shoot number. Observed differences for root characteristics did not correlate well with hardiness levels from the cultivars in either the greenhouse or field experiments.
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