Genotype x Environment Interaction and Yield-Stability Analyses of Rice Grown in Tropical Inland Swamp

Twelve rice varieties were cultivated in inland hydromorphic lowland over a four year-season period in tropical rainforest ecology to study the genotype x environment (GxE) interaction and yield stability and to determine the agronomic and environmental factors responsible for the interaction. Data on yield and agronomic characters and environmental variables were analyzed using the Additive Main Effect and Multiplicative Interaction (AMMI), Genotype and Genotype x Environment Interaction, GGE and the yield stability using the modified rank-sum statistic (YSi). AMMI analysis revealed environmental differences as accounting for 47.6% of the total variation. The genotype and GxE interaction accounted for 28.5% and 24% respectively. The first and second interaction axes captured 57% and 30% of the total variation due to GXE interaction. The analysis identified �TOX 3107� as having a combination of stable and average yield. The GGE captured 85.8%of the total GxE. �TOX 3226-53-2-2-2� and �ITA 230� were high yielding but adjudged unstable by AMMI. These two varieties along with �WITA 1� and �TOX 3180-32-2-1-3-5� were identified with good inland swamp environment, which is essentially moisture based. The two varieties (�TOX 3226-53-2-2-2� and �ITA 230�), which were equally considered unstable in yield by the stability variance, ?2i, were selected by YSi in addition to �TOX 3107�, �WITA 1�, �IR 8� and �M 55�. The statistic may positively complement AMMI and GGE in selecting varieties suited to specific locations with peculiar fluctuations in environmental indices. Correlation of PC scores with environmental and agronomic variables identified total rainfall up to the reproductive stage, variation in tillering ability and plant height as the most important factors underlying the GxE interaction. Additional information from the models can be positively utilized in varietal development for different ecologies

Genetic variability, heritability and genetic advance studies in top- cross and three-way cross maize (Zea mays L) hybrids

Understanding the genetic variability, heritability and genetic advance of traits in any plant population is an im- portant pre-requisite for selection program. This study was designed to assess the magnitude of genetic variabili- ty, heritability and genetic advance of traits in top-cross and three-way cross maize (Zea mays L) hybrids evaluated at three locations in South-Western Nigeria. The trial consisted of ten genotypes each of top-cross and three-way cross hybrids arranged in randomized complete block design with three replications. Data on grain yield and other desirable traits across the three locations were used to estimate the genetic variability parameters, heritability and genetic advance (GA). Highly significant (P ≤ 0.01) differences were detected within each hybrid class for all the traits. Traits evaluated in this study exhibited different levels of variability, heritability and genetic advance between the two hybrid classes. Low to moderate phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) were recorded. Also, low to very high heritability and low to high GA values were recorded for all the traits measured in the top-cross hybrids, whereas the three-way cross hybrids exhibited low to moderately high heritability estimates and low to moderate GA values. Grain yield and field weight showed moderate GCV, moderately high heritability and high GA values in top-cross hybrids. These characters exhibited moderate GCV but low heritability and GA values in three-way hybrids. More characters in top-cross hybrids revealed sufficient amount of variability than in three-way cross hybrids, thus offer scope for genetic improvement through selection

Genotypic performance, character correlations and path analysis of pod yield in Abelmoschus caillei (A. Chev.) Stevels

Direct selection based on pod yield is often a problem in West African okra (Abelmoschus caillei (A. Chev.) Stevels) breeding programs. Information on inter-relationships among traits to implement indirect selection for pod yield is needed. Objectives of this study were to evaluate the performance of West African okra varieties in two cropping seasons prevailing in Nigeria, and to determine the associations among main agronomic characters and their influence on pod yield. Twenty-five genotypes were grown in two planting seasons at the Research Farm of the Federal University of Agriculture, Abeokuta in 2008-2009 using a randomized complete-block design with three replications. Sixteen plant characters were measured. The data were subjected to variance, correlation and path analyses. Four genotypes, viz., CEN 010, CEN 012, NGAE-96-04 and AGA 97/066-5780 demonstrated potential for high pod yield. CEN 012 and AGA 97/066-5780 in addition, demonstrated early flowering higher number of pods. Character associations varied between planting seasons. The dependence of pod yield on final plant height, number of branches per plant, number of pods per branch, number of pods per plant, number of ridges per pod, weight of 250 seeds, pod length and seed weight per plant was noted in both planting seasons. In both seasons, number of pods per plant exhibited a high positive direct effect on pod yield. In conclusion, the trait of most interest for improving pod yield under early and late-season conditions was number of pods per plant