The adaptation of Medicago polymorpha to a range of edaphic and environmental conditions: effect of temperature on growth, and acidity stress on nodulation and nod gene induction

Abstract

Three experiments were conducted with Medicago polymorpha collected from a diverse range of sites in Sardinia, to investigate the relationship between edaphic and environmental conditions at collection sites, and the growth and nodulation of the genotype. Growth response to 2 temperature regimes (20/15¦C, 11/9¦C) was greater for genotypes collected from high altitude than for those from 1350 m. Shoot yield was more depressed by low temperature and more stimulated by high temperature in high altitude than low altitude genotypes. All genotypes nodulated when exposed to considerable acidity stress (pH 5.4) and 1 mmol Ca/L in solution culture. However, there were differences between genotypes in nodulation reduction caused by exposure to acidity. These differences were not well related to the soil pH at the site of collection, or to the effects of pH on the ability of root exudates from the genotypes to stimulate nod gene expression in Rhizobium meliloti.