1 Effects of testing environments and crop density on winter wheat yield

Stability of genotypes across different environments is one of the main goals in winter wheat breeding programs. Attention has been devoted to analysing genotype by environment interactions (GEI) to improve crop breeding success. Usually, strategy for selection of winter wheat is that selection should be made on several locations different in climatic and soil conditions. The objectives of this paper were to examine influence of different testing environments and sowing rates on formation of winter wheat kernel yield and, after the stability analysis, to identify most stabile genotypes and locations. Research work was conducted on 14 winter wheat genotypes and four testing locations in East Croatia. On each location genotypes were sown in two sowing rates – 300 and 600 germinable seeds m2. Examined genotypes included registrated cultivars (new and older one) and new breeding lines. Testing locations differs in average amount of rainfalls, average temperature and soil type. Combined analysis of variance showed highly significant (p≤0.01) influence of genotypes, environments (sowing rate and location) and GEI on kernel yield. AMMI 1 model biplot showed that the most yielding location, in commbination with higher sowing rate, was one with the best soil conditions (black soil-chernozem). Higher sowing rate at all locations showed higher yield than lower sowing rate at the same location. Biplot also showed that locations were spread from lower yielding to high yielding. Examined genotypes differed in yield and in stability accross environments. Genotype Lucija has the highest yield, but it was unstable and adapted to higher yielding environments. Best combination of high yield and good stability was in recognized cultivar Pipi and breeding line OSK 89/05