Path analysis of genotype x environment interactions of wheats to nitrogen

To determine the effect of the application of different levels of nitrogen on grain yield and its components, nine genotypes of bread wheat (Triticum aestivum L.), five of durum wheat (T. turgidum L. var. durum Deaf.) and a t riticale (x Triticosecale Wittmack) were subjected to three levels of N (0, 65 and 130 kg N ha(-1)) at three dates of planting: late planting, early p lanting and mid-season planting, over two growing seasons. A mathematical m odel based on the method of path analysis was used to study the relationshi p between grain yield and its components under different N levels. The main effect of N was highly significant for grain yield, aboveground dry matter at anthesis, number of kernels per spike and kernel weight. Genotype x N i nteraction was significant for these characters, except number of kernels p er spike. The greatest variability among the genotypes in response to N occ urred during vegetative growth, followed by the seed setting and grain fill ing periods. Seven genotypes showed sensitivity to N during vegetative grow th and seed setting, two during seed setting and grain filling, one during vegetative growth and grain filling and three during both vegetative and re productive phases. Only 'Express' and to some extent 'Yecora Rojo' were ada pted to limited N during the reproductive phase. Development and cultivatio n of cultivars such as Express that are adapted to limited N could reduce t he amount of N required to grow an economic crop and thus reduce the cost o f inputs and the possibility of polluting natural resources with the applic ation of excess N. ((C) Inra/Elsevier, Paris.).