BREEDING AND YIELD STABILITY OF WINTER-WH EAT

Breeding and yield stability of winter wheat. The yield stability of 1 2 :lines of winter wheat bred by INRA (Institut National de Recherche Agronomique) and 3 controls has been studied in the INRA network. The material was evaluated in randomized P-block designs, elementary plots measuring at least 5.9 m(2). Twenty-four various environments have be en studied over 3 seasons: 1990-1991, 1991-1992 and 1992-1993. They ar e combinations of levels of 3 factors: location, condition and year. E ach environment has been biologically described during the period of t he establishment of the number of grains per square meter and the grai n-filling period. The analysis of stability included environmental cha racteristics as covariates. These were defined in a previous descripti on and showed that the genotypes only behaved in a different way durin g the grain-filling period. In addition, the 2 models used for the ana lysis of interaction, joint regression and factorial regression showed that the behaviour of the INRA lines was quite different from that of controls. In contrast to controls, the genotypes selected in Rennes a re the most resistant to unfavourable conditions of the environment. T wo other entries, selected in Clermont-Ferrand and Estrees-Mons, are s imultaneously productive, stable, with good general adaptability and a rather good resistance to unfavourable conditions of environment, whi ch indicates that it is possible to associate hardiness and yield pote ntial in a breeding programme.