Abstract
The International Centre for Maize and Wheat Improvement (CIMMYT) develops maize (Zea mays L.) inbred lines and hybrids yearly that have several breeding and commercial attributes. However, no genetic analysis has been done on the recently developed inbred lines for yield performance under drought and low-N stress. The objectives of this study were to identify lines with positive general combining ability (GCA) effects for grain yield under stress environments and to identify the best single-cross hybrids with the highest specific combining ability (SCA) effects. Analysis of variance combined across sites showed significant mean squares for genotypes, locations and genotype by environment interaction (GEI) for grain yield. GCAlines, SCA and components of interaction effects were significant across sites. Additive genetic variance was more important than dominance variance in determining yield performance across locations indicating that selection based on grain yield under drought and low-N stress can be effective. Average grain yield across the eight locations ranged from 1.61 t ha-1 to 10.63 t ha-1 while narrow sense heritability for grain yield was 52.6% across sites and was slightly lower under managed drought and low-N stress. The testers CL115807 and CL106622 showed positive and significant GCA effects for yield performance under drought and low-N stress respectively. The best tester across all sites was CL115793 and line CZL0713 had consistently positive GCA effects for grain yield across sites. CML536 × CL115802 and CML312 × CL106508 were the best single crosses under low nitrogen stress sites while hybrid CML312 × C323-45 showed the highest positive SCA effects across sites. In conclusion, our results show that CIMMYT has new lines that have desirable adaptive attributes when grown under drought and low nitrogen stress environments in the mid-altitude region; hence these can be adopted for hybrid, synthetic and OPV formation.
Highlights
Drought and low-N stresses are factors that largely limit maize production in tropical environments (Bӓnziger et al, 1999; Edmeades et al, 1999; Bӓnziger & Diallo, 2001; Diallo et al, 2001)
The 240 hybrids developed were planted alongside 10 checks: two checks from Seed Co (SC 727 and SC 633) and eight checks developed by CIMMYT (CML444 × CML536, CML395 × CML444, CML312 × 442, CML539 × CML 442, CML539 × CML197, CML312 × CML444, CML444 × CML197 and CML444 × CML489)
The significant genotypic variation for grain yield performance observed in this study indicates that, good progress can be made in selecting for improved grain yield under drought and low-N stress environments
Summary
Drought and low-N stresses are factors that largely limit maize production in tropical environments (Bӓnziger et al, 1999; Edmeades et al, 1999; Bӓnziger & Diallo, 2001; Diallo et al, 2001). Yield declines are being noticed in the productive mid-altitude eco-zones of central and southern Africa (Diallo et al, 2001). Development of maize hybrids that can adapt to these stresses is important (Hoisington, 2001; Betrán et al, 2003; Bӓnziger et al, 2004). Abiotic stress tolerance is one of the most studied traits at CIMMYT, especially tolerance to drought (Hoisington, 2001). Plants vary in their ability to withstand abiotic stresses, both between species and within populations of single species. One of the most challenging traits to breed for, among abiotic stresses is drought tolerance, due to its unpredictable nature (Hoisington, 2001)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
