Genotype X Environment Interaction Of Imiadazolinone Resistant Maize Genotypes For Yield Under Striga Infestation

Twenty-five imidazolinone resistant (IR) maize genotypes were laid down in 5x5 simple lattice designrnwith 2 replications at six striga infested and five striga free environments during 2006/07 croppingrnseason. The objectives of the study were to evaluate IR maize genotypes for grain yield andrnadaptability under striga infestation and free field conditions, to determine the magnitude ofrngenotype-by-environment interaction (GEI) of IR maize genotypes for grain yield, to determinernstability of yield performance among the IR maize genotypes and identify the stable genotype(s) andrnthose with adaptation to specific environments and to study the correlation among various stabilityrnparameters. For trials where successful striga infestation was achieved, yield was reduced on averagernfrom 8.62 to 26.87 Q/ha. The average percent reduction in yield for all the IR maize genotypes wasrn40.40% whereas for the standard check, WH-403 it was 65.00%. The highest percent reduction due tornstriga infestation was observed on WH-403 at Alupe (79.00%) and Kibos (75.54%). Under striga freerncondition, WH-403 gave the highest mean yield of 42.28 Q/ha but with only 3.37% yield advantagernover the highest yielding IR genotype, INTA/CML390/373 while under striga infested field the highestrnyielding IR genotype, CML445/390/373 had a yield advantage of 86.50% over WH-403 showing thernsuperiority of IR maize genotypes under striga infestation. Combined ANOVA revealed highlyrnsignificant effects of the environments, genotypes and GEI. The presence of significant GEI showedrnthe inconsistency in performance of maize genotypes across the 11 environments. Six statisticalrnmethods were conducted to determine yield stability. Results of additive main effects andrnmultiplicative interaction ( AMMI) analysis showed that out of 11 interaction principal componentrnaxis (IPCAs) only the first two IPCAs were found to be highly significant and cumulatively contributedrn58% of the total GEI while linear regression explained only 6% of the total GEI. Spearman’srncoefficient of rank correlation between mean yield and regression coefficient ( irn ), stability variancern(2i ), ecovalence (Wi) and deviation from regression ( dirn 2 ) was positive and significant, but therernwas non-significant correlation between mean yield and coefficient of variation (CV) and AMMIrnstability value (ASV). Since ASV explains interaction effects and provides agronomically meaningfulrninsights into the data structure, it is better if used as stability measure for reliable selections of stablerngenotypes. Based on most of the stability parameters estimated, the three-way cross maize hybrid,rnCML78/390/202 and the late maturing maize OPV, ECA-144, were found to be the most stable.rnKey Words: AMMI, ASV, GEI, Maize, IR, Stability, Striga

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