Genotypic Differences in Tolerance to Stress Imposed by Defoliation and Plant Density in three Maize Hybrids

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Anderson, R.C.
DaITah, L.L.
Zuber, M.S .
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Our Objective was to evaluate methods of identifying stress tolerance among maize (Zea mays L.) genotypes. We studied the stress effects of three defoliation treatments, two nitrogen levels, and 'two plant densities on the yields of three hybrids. Yield was significantly affected by defoliation treatments. The plant density-by-hybrid and defoliation treatment-'by-hybrid inter action were also significant. When the portion of the plant above the ear was removed 3 days post-silking. Pioneer Brand 3388, B73 x Mo17, and C103 x C121E HtHt showed 17 percent, 24 percent, and 49 percent yield reductions, respectively. The pattern was similar when the hybrids were grown at normal (53,600 plants/ ha) and high (107, 200 plants/ha) plant densities. Y'ie1ds 'Of Pioneer Brand 3388 and Mo17 were not significantly affected by high plant density, while that of C103 x C121 HtHt was reduced by 29 percent. Rate of ,nitrogen fertilization had little effect on hybrids' responses. High plant density topping the plant should be a useful procedure for selecting genotypes more tolerant to segregating population to determine whether either of these treatments would be successful in improving general stress tolerance trough selection.
East African Agricultural And Forestry Journal, XLV (NO1), pp. 69-73