Browsing by Author "Ochieng, J.A.W."
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Item Cross Hybrids of Maize Under Stress and Non-Stress Environments(1995) Ochieng, J.A.W.; Muthokat, D.K.; Kamidi, R.E.; Kenya Agricultural Research InstituteIn a study to identify high yielding, stable single cross (SC) maize hybrids for commercial use, SCs were formed from eight lines. Three were from Kitale Station Maize, one from cycle two (C2) of Kitale Synthetic II and four from Ecuador 573 (at C2, C3, C4 and C6). Analyses were performed on data obtained from the evaluation of 28 SC hybrids in three replications at three high altitude locations in Kenya in 1986 and 1988. Each location experienced drought stress in one year and no stress in the other. Overall, yield was reduced by 37% under moisture stress. There was no genotypic variation for percent plant stand. However, significant (p≥0.05) genotypic variation, free of interactions, was observed for ear height. Differences among the genotypes for grain yield, open-tip ears and days to mid-anthesis were masked by genotype x location x year interaction. Experimental hybrids K3 x E6 and Kl x E8 were the highest yielding commercial type SC hybrids at 7.56 and 7.50 tons/ha, respectively. Of these, Kl x E8 had 5.0 cm lower ear placement, 24.6% less open-tip ears, 11 % more standing plants and 2 days 7 less to mid-anthesis than K3 X E6, and was deemed superior. Besides, SC KI x E8 exhibited the highest stability over environments (β = 1.128 ± 0.078), compared to K3 x E6 (β= 0.878 ± 0.310). The best local x local SC (K3 x K4) yielded 6.41 tons/ha and the best exotic x exotic SC (83 x E7) yielded 4.55 tons/ha. These two SCs were as tall, or taller, and at least 5 days later in anthesis than either Kl x E8 or K3 x E6. Husk cover expression of the parental lines was reflected in their SCs in a manner suggestive of a non-additive effect for this trait. Grain yield was correlated positively with ear height, but negatively with days to mid-anthesis. Lack of correlation between ear height and days to mid-anthesis implied that selection for the two traits may proceed independently. The results obtained herein demonstrate the feasibility of developing high yielding, environmentally stable, commercial-type SC hybrids. Efforts should be made to identify high yielding seed parents in order to reduce risks and costs in seed production.Item Genetic Effects from Long-Term Selection in Populations of Maize (Zea mays L.)(Joseph A. W. Ochieng, 1993) Ochieng, J.A.W.The ultimate objective of a crop improvement program is to identify genetically superior genotypes to be used as cultivars. The stability of a cultivar in space and in time is crucial to its practical usefulness over a range of environments. Routinely, plant breeders apply recurrent selection techniques to increase the frequency of alleles favorable to the quantitative trait of interest and, consequently, to increase the probability of being able to identify desirable genotypes. For maize (Zea mays L) there is an option to apply either intra-population or inter-population selection to improve a breeding population.Item Relation Of maize kernel Breakage Susceptibility To Rice Weevil Damage(Joseph A. W. Ochieng, 1981) Ochieng, J.A.W.Maize (Zea mays L.) is the staple food crop for the majority of Kenya people. The crop is grown on large scale farms as well as in small-holdings. The latter category of farms accounts for the greater proportion of maize production. The Kenya government has a policy of self-sufficiency in maize production. Such a policy is economically sound as this saves the foreign exchange that would otherwise be spent on importation.
