RELATIONSHIPS AMONG INTERNATIONAL TESTING SITES OF SPRING DURUM-WHEAT

Knowledge of the relationships among international test sites is valua ble information for effective targeting of germplasm exchange. Five ye ars of grain yield data from the Elite Durum Yield Trial (EDYT), consi sting of 132 trials from 32 locations in 22 countries, were studied. P attern analysis, the combination of ordination and cluster analysis, w as used to identify groupings of international test sites that represe nt similar selection environments and compare location association wit h the mega-environment designations of the International Maize and Whe at Improvement Center (CIMMYT) breeding program. Two main environmenta l groups and six subgroups were identified for durum wheat (Triticum t urgidum L. var. durum). The major determinants of the groupings were l atitude and moisture supply. Biotic and abiotic stresses influenced fu rther delineation of the clusters. Discrepancies between mega-environm ent designation and pattern analysis results warrant further investiga tions of the underlying causes. The relationships among test sites doc umented in this study should provide a framework for effectively targe ting germplasm and information exchange between comparable programs.