Identification of Elite, High Yielding and Stable Maize Cultivars for Rwandan Mid-altitude Environments

Abstract

Environmental and biotic stresses, such as drought, low fertility, diseases and weeds, are causing annual losses of million tons of maize grain in sub-Saharan Africa. The utilization of drought tolerant, extra-early maturing, disease and insect resistant maize varieties with Nitrogen Use Efficiency (NUE), has boosted maize production in areas where drought and disease are severe. Experiments were conducted with the objective of identifying suitable maize varieties for the mid-altitude environment that are tolerant to drought and resistant to infestations of Maize Streak Virus (MSV) and Turcicum Leaf Blight (TLB). The experiments were conducted in four sites (Rubona, Bugarama, Nyagatare, Karama) in Rwanda during the 2009 B and 2010 A seasons. They consisted of nine new hybrid varieties, seven new open pollinated varieties (OPVs), one hybrid check and four OPV checks. The AMMI (Additive Main Effects and Multiplicative Interaction) model for grain yield was used to analyse data. It showed that grain yield variation due to environments, genotypes and Genotype by Environment Interaction (GEI) was highly significant (p < 0.01). However, genotype effects accounted for 53 % of the sums of squares of treatments while environment accounted for 31 % and GEI effects for 16 %. The AMMI 1 biplot showed that drought tolerant and extra-early maturing cultivars were the most stable across environments. The AMMI 2 biplot showed that two OPVs were the least sensitive to the changes in the environments, and harsh environments exerted strong interactive forces on genotypes. Analysis of AMMI 1 and AMMI 2 biplots allowed six elite cultivars to be identified for the mid-altitudes which were stable across environments —CML442/CML440//CML445 (9.77 t/ha), CML312/CML202//CML445 (8.79 t/ha), CML144/CML159//CML182 (8.02 t/ha), NYA1 (Pop Nyag) (8.70 t/ha), RUB2 (DTLWN1) (7.99 t/ha) and ECA_EPOP1 (5.88 t/ha). The hybrid variety CML442/CML440//CML445 was drought tolerant, hence it was suitable for the semi-arid mid-altitudes; the hybrid cultivar CML312/CML202//CML445 combined resistance to MSV and TLB. The hybrid variety CML144/CML159//CML182 was a Quality Protein Maize (QPM). The OPV NYA1 combined several traits including earliness, resistance to foliar diseases and tolerance to drought. The variety RUB2 had desirable grain quality in addition to resistance to foliar diseases. Variety ECA_EPOP1 was extra-early and attained full maturity in 100 days after planting.