Genetic variances and relationship among traits of an early maturing maize population under drought-stress and low nitrogen environments

Article purchasedDrought and low soil nitrogen (low N) are major causes of low grain yield of maize (Zea mays L.) in sub-Saharan Africa (SSA). An early maturing maize population, TZE-Y Pop DT STR, had undergone four cycles of selection for drought tolerance, followed by four selection cycles for resistance to Striga hermonthica (Del.) Benth., which is normally conducted under low N (about 30 kg N ha-1). The objectives of this study were to estimate residual genetic variances, predict future gains from selection, and investigate inter-trait relationships in the population under drought-stress, low N and across research environments. North Carolina Design I was used to develop 250 full-sib progenies from the improved population, which were evaluated in three drought-stress and two low N environments in Nigeria, 2011 to 2013. Additive genetic variances were not significant for most traits under the research conditions. The predicted gains from selection for grain yield were 5.3, 8.5 and 7.5% cycle-1 under drought, low N, and across environments. These results suggested the absence of substantial genetic variability in the population to ensure progress from selection. Ears per plant (EPP), ear aspect (EASP), plant aspect (PASP), and stay green characteristic (STGR) were consistently identified as important secondary traits under both research conditions. We concluded that there is need to introgress new sources of favorable alleles for drought-stress and low N tolerance into the population for guaranteed progress from selection, using EPP, EASP, PASP, and STGR in combination with yield in a selection index under drought-stress and low N

Yield gains in extra-early maize cultivars of three breeding eras under multiple environments

Open Access JournalAvailability of extra-early maize cultivars has facilitated the expansion of maize production into savannas of West and Central Africa (WCA). Fifty-six extra-early maize cultivars of three breeding eras;1995 to 2000, 2001 to 2006, and 2007 to 2012 were evaluated for 2 yr under 24 multiple-stress and 28 non-stress environments in WCA. Objectives of the study were to determine genetic improvement in grain yield of cultivars developed during the breeding eras, and identify high-yielding and s multiple-stress and non-stress environments. Yield gains from era 1 to era 3 under multiple stresses was associated with increased days to anthesis, reduced stalk lodging, and improved husk cover. Cultivars 2004 TZEE-Y Pop STR C4, TZEE-W Pop STR QPM C0, and TZEE-W Pop STR BC2 C0 of era 2; and TZEE-W STR 107 BC1, TZEE-W Pop STR C5, and 2012 TZEE-Y DT STR C5 of era 3 were high-yielding and stable across multiple-stress environments while 98 Syn EE-W from era 1, FERKE TZEE-W STR, TZEE-W Pop STR C3, and TZEE-Y Pop STR QPM C0 from era 2, and TZEE-W Pop STR C5, 2009 TZEE-OR2 STR QPM, 2009 TZEE-W STR, TZEE-Y STR 106, and TZEE-W DT C0 STR C5 from era 3 were outstanding across non-stress environments and should be tested extensively and commercialized. Considerable improvement has been made in breeding for multiple-stress tolerant extra-early maize cultivars

Maize genetic improvement for enhanced productivity gains in West and Central Africa

During the past 45 years, the genetic improvement programs of IITA and its partners have made spectacular progress in developing high-yielding crop varieties that offered best-bet solutions to major production constraints, such as, cassava mosaic, maize streak, Striga, soybean rust, insect pests, and even drought. These have led to dramatic increases in the production of cassava, maize, soybean, cowpea, and yam in sub-Saharan Africa that have directly contributed to increases in food availability and indirectly to improvements in national economies. This section presents the status, progress, and achievements, and also outlines future work on crop improvement by genetic enhancement in IITA's six crops

Assessment of interrelationships among grain yield and secondary traits of early-maturing maize inbred lines under drought and well-watered conditions

Knowledge and understanding of interrelationships between grain yield and yield-related traits would ensure progress from selection in maize breeding programs through the use of appropriate selection indices. One hundred and fifty-sixearly-maturing maize inbreds were evaluated at fiveenvironments in Nigeria, for 2 years to assess the relationship between grain yield and yield-related traits of maize inbreds under drought and well-watered conditions. Genotypes, and genotype × environment interaction mean squares were significant(P<0.05) for grain yield and other measured traits under drought and well-watered conditions. Under drought, plant and ear aspects, ear height, ears per plant (EPP), leaf senescence, number of seeds per ear, and seeds per row had direct effects on grain yield, accounting for 76% of total variation. Under well-watered conditions, days to silking, ear aspect, ear height, EPP, ear length, 100-kernel weight, number of seeds per row, plant height, and stalk lodging had significantdirect effects on yield. Genotype main effect plus genotype × environment interaction (GGE) biplot identifiedplant and ear aspects, days to anthesis and silking, ASI, EPP, stay green characteristic, plant and ear heights, ear diameter, number of seeds per ear, number of seeds per row, and ear length as the most reliable traits for indirect selection for grain yield improvement under both research conditions. Plant and ear aspects, ear height, stay green characteristic, number of seeds per ear, and number of seeds per row were identifiedby both path–coefficientand GGE biplot analyses as the most reliable traits for selecting for grain yield under drought. Ear aspect, EPP, days to silking, plant and ear heights, number of seeds per row, and ear length were the most reliable traits for selecting for improved grain yield under well-watered conditions

Biplot Analysis of Line × Tester Data of Maize (Zea mays L.) Inbred Lines under Stress and Nonstress Environments

The GGE biplot tool has potential for determining combining ability effects, identifying distinct heterotic groups and efficient testers in a line × tester study. However, its use for such analysis has not been adequately explored. The objectives of this study were to (i) assess combining ability of extra-early maturing lines (80–85 days to physiological maturity) and testers for grain yield (ii) classify lines into heterotic groups and (iii) identify most efficient testers using GGE biplot. Sixty-three lines crossed to four testers were evaluated under Strga-infested, drought and nonstress environments for 2 years in Nigeria. Results of GGE biplot analyses of combining ability and heterotic patterns of yield of lines, grouping and identification of testers were close to those of the conventional line × tester method. Testers TZEEI 13, TZEEI 21 and TZEEI 29 were highly efficient in grouping lines under stress environments while testers TZEEI 21 and TZEEI 29 were best under nonstress environments. The GGE biplot identified tester TZEEI 13, TZEEI 21 and TZEEI 29 as most efficient across stress environments and TZEEI 21 and TZEEI 29 across nonstress environments