Effect of Number of Seed Bulked and Population Size on Genetic Variability When Using the Multiple-Seed Procedure of SSD
2001
Macchiavelli, Raul | Beaver, James S.
Single-seed descent is used by grain legume breeders to maintain genetic variability in populations of advanced generation lines. To reduce labor costs, breeders often use a multiple-seed procedure in which a single pod rather than a single seed is harvested from each plant and bulked. This paper studied the distribution of the proportion of original F₂ plants represented after advancing populations ranging from 100 to 600 plants from the F₂ to the F₆ generation when the multiple-seed procedure of SSD is used. Since the analytical solution to this problem is intractable, involving a 4-fold convolution of a hypergeometric distribution, a simulation was run in SAS to estimate this probability distribution. An increase in the size of the population advanced from the F₂ to the F₆ generation did not influence significantly the mean proportion of F₂ plants represented in the F₆ generation but decreased its variability. An increase in the number of seed per pod from two to six reduced the mean proportion of F₂ plants represented in the F₆ generation from 0.45 to 0.35, but did not decrease significantly the standard deviations of the distributions. Using the multiple-seed procedure, grain legume breeders could expect, on the average, that at least every third F₆ line would be derived from a different F₂ plant. This should generate considerable genetic variability for the selection for quantitatively inherited traits such as seed yield.
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