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An important task of multienvironment trials (MET) analysis is evaluation of testing sites for megaenvironment diff erentiation and selection of "ideal" candidate location to improve the effi ciency of cultivar selection and recommendation. Th e objectives of this research work were (i) to divide the Spanish cotton (Gossypium hirsutum L.) testing locations into megaenvironments and (ii) to separate the testing locations based on their distance to the "ideal" location, discriminating ability, representativeness, and uniqueness. GGE biplot was employed to analyze eight 1-yr and two multiyear (3-yr, 4-yr) balanced datasets from 1999 to 2006 cotton trials of Delta & Pine Land Co. in Spain for yield, fi ber quality traits, a selection index (SI) based on yield and quality, and Verticillium wilt (Verticillium dahliae Kleb.) disease infestation level. Yearly GGE biplots revealed crossover genotype × location interactions, but not large enough to divide the area into diff erent megaenvironments. Th erefore, the Spanish cotton region may be considered as a complex megaenvironment and cultivar recommendation may be based on both mean performance and stability. Las Cabezas location was the closest to an ideal based on both yield and the SI regardless of the change from plastic to nonplastic mulching cultural practice. Aznalcazar did not provide unique information and could be dropped as a test site. Th e separation of test locations for their discriminating ability and representativeness provided useful information on the eff ectiveness of each testing location for developing and/or recommending cultivars with specifi c or broad adaptation. In this sense, Lebrija could be considered as trait-specifi c selection environment for early screening of verticillium tolerant genotypes.Abbreviations: AMMI, additive main eff ects and multiplicative interaction; GEI, genotype × environment interaction; GGE, genotype main eff ect plus genotype × environment interaction; MET, multienvironment trials; PC, principal component; SI, selection index.

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