ADAPTATION PATTERNS AND DEFINITION OF MACRO-ENVIRONMENTS FOR SELECTION AND RECOMMENDATION OF COMMON-WHEAT GENOTYPES IN ITALY

Eighteen common-wheat varieties grown for three seasons at 31 location s in Italy were used to study the relationships between cultivar adapt ation patterns, climatic factors and morphophysiological traits of gen otypes, as well as defining macro-environments for the selection and r ecommendation of genotypes in the region. The variances of both the ge notype-location and genotype-season interactions were significant, the former being almost 80 % greater than the latter. Some 10.4 % of geno type-location interaction was accounted for by heterogeneity of genoty pe regressions on site mean, 38.0 % by the first two axes of a princip al components analysis and 32.0 % by definition of four macro-enviroam ents. Occurrence of genotype-location interaction was related to the l evel of late frosts, winter cold, and late drought and heat stress at each location, and to heading date and tolerance of frost, Septoria bl otch and lodging in each genotype. Following estimates of broad-sense heritability, breeding for specific adaptation may be envisaged for no rthern and central Italy on the one hand, and southern Italy on the ot her. Morphophysiological traits contributing to better performance in each of these macro-environments were indicated.