Line by Tester Analysis of Elite Tropical-temperate Maize Lines Under Water-stress and Non-stress Environments
Abstract
Maize is the second most cultivated cereal crop in the world after wheat. In spite of its
importance, the production challenges have continuously led to poor yields in sub-Saharan
Africa. This has called for need to improve varieties that are adapted to the tropical ecosystem.
The aims of this study were (i) to assess the combining ability of the tropical-temperate maize
lines for grain yield, drought tolerance, disease resistance, and heritability of the traits, and (ii) to
examine the yield and yield stability of the three-way cross hybrids in eight environments found
in different agro-ecological environments and identify the genotypes, of wide or specific
adaptation. The maize germplasm used in this study were obtained from various sources. These
included seven elite tropical-temperate inbred lines (L), seven single cross testers (T) and six
commercial hybrids that were used as checks during evaluation. The results indicated that inbred
lines L5 and L3 gave high grain yield across well-watered environments and had a common
single cross tester T6, with best linear unbiased estimates values of 8.5 t/ha and 8.4 t/ha,
respectively. The two lowest hybrids across locations had a common single cross tester, T7, with
two different pollen donors L6 and L7 yielding 6.0 t/ha and 5.5 t/ha, respectively. Forty eight
hybrids had statistically better mean grain yield than the best check, Pioneer 3253. Under
managed drought stress conditions, the top two performers in grain yield had different testers,
namely T6 and T4 but shared the same pollen donor, L5, with values of 4.9 t/ha and 4.8 t/ha,
respectively. DK8053 was the best check with value 3.7 t/ha. The results indicated that the
inbred lines which produced the top yielding hybrids were related by pedigree and origin. To
examine genotype × environment interaction and yield stability, the three-way cross hybrids
were planted in eight environments with two replications. Data was analyzed using REML, SAS
and GGE biplot tools. The results revealed that Environment (E) contributed 67% of the total
sum of squares for grain yield while GEI and genotypes (G) contributed a percentage of 12.5%
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and 10.3%, respectively. The first two principal components (PCs) accounted for 67.9% total
variation. The biplot figures demonstrated that across environments, entry 10 (L5 × T5), 14 (L5
× T3) and 28 (L3 × T3) were the highest yielding with stable genotypes. The additive or
dominance gene action played a greater role in the inheritance of grain yield and the yield related
agronomic traits. There were two mega-environments (ME) with ME1 represented by 3 locations
and ME2 by 5 locations. The two testers included as checks in this study showed that tester 2
performed better under drought conditions and therefore it is a recommended hybrid for yield
increase in water stress environments. Tester 5 should be utilized in Kirinyaga type moisture
regimes, as it yielded higher than all experimental hybrids. L1, L3 and L6 could contribute to
formation of hybrids with consistent earliness, while L5 contributes to stable high grain yield in
both well-watered and water stress conditions. The heritability of most agronomic traits was
noted implying that the traits characteristics can be passed to future generations. Tropical maize
populations can be improved for these traits using these improved maize germplasm. The
promising maize hybrids for yield and agronomic traits could be nominated for national
performance trials for commercial release in various Eastern African countries
Publisher
University of Nairobi
Rights
Attribution-NonCommercial-NoDerivs 3.0 United StatesUsage Rights
http://creativecommons.org/licenses/by-nc-nd/3.0/us/Collections
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