Biological nitrogen fixation and biomass production stability in alfalfa (Medicago sativa L.) genotypes under organic management conditions

Assessments of the stability as well as the performance of plant genotypes across diverse environmental conditions is important for plant breeders as a tool for selecting superior cultivars for the target environments. Alfalfa is the best known fodder crop with a high ability for biological nitrogen fixation (BNF) and high drought tolerance, and it is well-known as an important component of organic farming systems especially in the dry, Pannonian region of east Austria. In a 2-year experiment (2007-2008), 18 alfalfa genotypes from different geographical origins were evaluated under irrigated and rainfed conditions in order to recognize high performance and stable genotypes based on biomass production and BNF in organically managed fields at the University of Natural Resources and Life Sciences, Vienna, Austria. The analysis of variance showed significant differences for the main factors namely year, location, genotype and their interactions in the studied traits. With regard to mean comparisons and stability analysis for shoot dry matter, total biomass yield and BNF, the cultivar Sitel was the best performing genotype followed by PlatoZS, Fix232, Vlasta and Gharghologh. Although additive main effects and multiplicative interaction analysis was found to be more informative in describing the adaptive response of the genotypes, the superiority measure P-i was the best stability parameter to select high yielding and stable genotypes, based on its simplicity of calculation and correlation with crop performance in this study.