Seedling vigour as a selection criterion in breeding maize under water stress
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The study was carried out between 1986 and 1988 to investigate the relationships between flowering habit, plant phenotypic appearance, seedling vigour and grain yielding ability while breeding early maturing maize. Four rainfed and four irrigated trials were conducted in a semi-arid area of eastern Kenya with two growing seasons per year, the long and the short rains. In the first group of trials, comprising Experiment 1, relationships between the various traits of interest were studied within cultivars that have been developed by the programme at Katumani, a breeding centre located in the area of interest. In Experiment 2, Sl selection was practiced on the same materials looking for early and for late flowering plants within a population of 2,000 plants per cultivar. Results from both experiments showed similar relative changes, although of lesser magnitude in Experiment 2. Seedling vigour was positively correlated with grain yield and was not correlated with flowering time and, therefore, maturity. Unlike grain yield, seedling vigour interacted little with the environment of growth. Experimental precision seemed to increase with additional water applied as irrigation. It was concluded that current cultivars have scope to be improved using good plant type and seedling vigour as the major selection criteria for yield. It was also concluded that selection could be aided by irrigating some of the trials to increase the environmental range covered, especially during the long rains season which was evidently the less reliable.