Modeling Genotype By Environment Interaction Of Eucalyptus Using Additive Main Effects And Multiplicative Interaction Approach
Karuntimi, Stephen Mbaabu
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Selection of eucalyptus genotypes with wide adaptability across diverse environments IS important for adoption recommendation. When selecting superior genotypes one is usually confronted with the problem of genotype by environment interaction. An extension of analysis of variance (ANOVA) for studying genotype by environment interaction (GEl) is Additive Main Effects and Multiplicative Interaction (AMMI) Model, which is a hybrid analysis that incorporates both additive and multiplicative components of a two way data structure. This study applied AMMI to evaluate genotype by environment interaction of eucalyptus species in Kenya grown at different locations, determined genotypes stability and pattern of response across environmental sites. The model is applied to data on eucalyptus research undertaken by Kenya Forestry Research Institute (KEFRI) for the tree improvement programme from 1998 and assessed till 2006 with an aim of determining stable and adaptable genotypes across the diverse environmental sites. The trials were set in a randomized complete..block design replicated two to four times. The combined analysis of variance indicates that environments (E), genotypes (G) and genotype by environment interaction (GEl) effects were significant, suggesting differential responses of the genotypes and the need for stability analysis. Analysis of variance for AMMI model revealed that two interaction principal components (IPCAs) were significant by using Gollob's F- test and accounted for over 90o/~of GE interaction. Therefore, successful genotypes need to be adapted to a broad range of environmental conditions in Kenya in order to ensure their yield stability and economic profitability. Of the Eucalyptus hybrid clones experimented across sites GC 14 ,GC 581, and GC 642 were found to be most stable genotypes for the highlands while GC 540 ,GC 514, and GC 14 were found to be most stable genotypes for the lowland environments implying they can be planted in a wide range of environments similar to the one tried. This resolves the complication of tree breeding program, where breeders are particularly interested in searching for fewer- widely adapted genotypes. The interaction was best predicted by the first two principal components of genotypes and environments. Consequently, bi-plots generated using genotypic and environmental scores of the first two AMMI components can help breeders have an overall picture of the behavior of the genotypes, the environments and GEls. The AMMI and ASV were found useful in describing GEl of various eucalyptus clones. Key words: Eucalyptus clones, genotype by environment interaction (GEl) and Additive Main effect Multiplicative Interaction (AMMI).