Crop diagnosis and probe genotypes for interpreting genotype environment interaction in winter wheat trials

Genotype*environment interaction has been analyzed with 12 genotypes and fo ur probe genotypes in French wheat trials. An integrated approach was devel oped which combined crop diagnosis with the analysis of interaction by fact orial regression Crop diagnosis was helpful to characterize the environment s and to select environmental variables. Such an approach succeeded in prov iding an agronomic explanation of genotype*environment interaction and in d efining the responses or parameters for each genotype and each environment. Earliness at heading, susceptibility to powdery mildew and susceptibility to lodging were the three major genotypic covariates. Interaction could als o be related to environment features, measured indirectly by the behavior o f the four probe genotypes during the formation of yield, what we called th e outputs of a simplified crop diagnosis, or described directly by indicato rs of yield-limiting factors. Two important crop diagnosis covariates were analyzed in order to characterize interaction during the formation of yield : the reduction in kernel number, which described the time-period until flo wering, and the reduction in thousand kernel weight, which corresponded to the period after flowering. These variates were estimated for each probe ge notype and allowed us to compare the behavior of the 12 genotypes to that o f the probe genotypes. Both periods of the formation of yield contributed t o the interaction, and 'Camp-Remy' was the probe of particular interest for the comparisons. When true environmental variates were used, factorial reg ression revealed that water deficits during the formation of grain number a nd level of nitrogen were predominant. Such an integrated approach could be exploited when varieties are tested in a network where numerous and divers e yield-limiting factors may occur.