Combining ability and heterosis for yield and yield components in peas (pisum sativum l.)
Pea production in Kenya is relatively low mainly due to diseases, pests and use of unimproved cultivars. Pea is an important and cheaper source of protein for majority of the population. This study was designed to determine the relationship between seed yield and its components and the nature of gene action and heterosis for yield, yield components and other plant traits in some of the pea cultivars grown in Kenya. Seven cultivars of peas (Pi sum sativum L.) were crossed in a half-diallel crossing system and the parents together with their F4 hybrids evaluated for seed yield' per hectare, 100-seed weight, seeds per pod, number of pods per plant, pod length, number of primary branches per plant, plant height and days to flowering at Kabete and Kinangop during the long rain season of 1989. The experimental design used was a randomised complete block design with 3 replications at each location. General and specific combining abilities were determined by Griffing's (1956a) Method 2, Model 1. The genotypes were found to differ significantly (P = 0.001) for all characters studied at both locations. Seed yield per hectare was found to be positively correlated with all the other characters studied. However, it was only significantly correlated with seeds per pod, pods per plant, branches per plant and plant height. These yield components can be utilised in the selection for yield improvement. Yield heterosis of the F1 based on the midparent value averaged 65% over locations. Among the parental cultivars, Nyaritho was the best combiner for seed yield per plant, pods per plant, branches per plant, plant height and days to flowering while Carouby was the best combiner for 100-seed weight, seeds per pod and pod length. None of the hybrids flowered earlier than the early parent at both locations. Scout was found to impart earliness to its progeny. Both general and specific combining abilities were responsible for the manifestation of variability for all the traits studied except pod length, seeds/pod and 100-seed weight where specific combining ability was of no importance. However general combining ability was more important than specific combining ability for all the traits. All the characters were found to be strongly influenced by the environment.
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