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Estimation of synthetic variety yields in pearl millet through parental line evaluation, per se and in tester combinations
Abstract
Three pearl millet (Pennisetum glaucum (L.) R. Br.) synthetic varieties were synthesized each from a different designated set of unrelated parental lines. Each set of parental lines was evaluated for general combining ability in two ways: (a) through a sample of paired testcrosses in a central circulant partial diallel; and (b) through topcrosses using a common unrelated variety tester. The two methods agree in identifying parental lines with good and poor combining abilities. Yield for each of all possible single cross hybrids in each set were predicted by summing the actual mean yield of the F$\sb1$'s and the general combining abilities of the two parents involved in the cross. Predicted mean yields of the F$\sb1$'s were equal to the actual mean yield of the F$\sb1$'s. The mean yields of the F$\sb1$'s and mean per se yield of the parental lines were used to predict yields of synthetic varieties. Two formulae: (1) Wright's; and (2) Busbice's were used to predict yields of synthetic varieties. Predicted yields of the synthetic varieties using Wright's and Busbice's formulae were similar. Predicted synthetic variety yields using combining abilities derived from topcrosses were 12% higher than predicted yields using testcrosses. Comparison of predicted and actual yield or Syn 3 showed that predictions using testcrosses were similar to the actual yield and those using topcrosses were 17% higher than the actual yield. Although topcrosses and testcrosses are both useful in selecting parental lines for a synthetic variety, based on general combining ability, the use of heterosis derived from topcross F$\sb1$'s to predict yield of a synthetic variety, either through Wright's or Busbice's formula is inappropriate. Only testcrosses provide information on average heterosis that is comparable to the expected heterosis in a synthetic variety. The proportion of selfing in pearl millet populations influences the predictions, estimates at 20% selfing seem to be close to the actual performance. Average synthetic variety yields were 30% over the mean yield of the parental lines, showing a considerable amount of heterosis. The highest yielding synthetic variety was made from a set of parental lines that had a high mean yield and a high mean yield of the F$\sb1$'s. The parental worth for yield is shown to be positively correlated to that for plant height. Plant height and days to bloom in synthetic varieties can be predicted in the same way yield is predicted.
Subject Area
Agronomy|Genetics
Recommended Citation
Chirwa, Rowland Morgan, "Estimation of synthetic variety yields in pearl millet through parental line evaluation, per se and in tester combinations" (1991). ETD collection for University of Nebraska-Lincoln. AAI9208102.
https://digitalcommons.unl.edu/dissertations/AAI9208102