Genotype by environment interactions of lucerne (Medicago sativa L.) in a cool temperate climate

Genotype by environmental interactions in lucerne (Medicago sativa L.) present considerable challenges when selecting an appropriate cultivar for a particular location and farming system. Data on the yield and persistence of a range of lucerne cultivars and experimental lines grown in two Tasmanian environments, Forth (41.20°S, 146.27°E, Red Ferrosol soil, under cutting with high fertiliser inputs, i.e. a high yield potential environment) and Cranbook (42.00°S, 148.03°E, Red Ferrosol soil, under grazing with low fertiliser inputs, i.e. a low yield potential environment) were examined using winter activity class as the experimental factor. At Forth, winter-dormant lucernes were the lowest yielding genotypes. In contrast, at Cranbrook, highly winter-active genotypes had lower plant persistence and dry matter yield than winter-dormant genotypes. Modified joint linear regression analysis showed that in a cool temperate climate, winter-dormant genotypes are more suited to a low yield potential environment, whereas highly winter-active genotypes are adapted to a high yield potential environment. Both the semi-winter-dormant and the winter-active genotypes were adapted to all environments. The dry matter yield of winter-dormant and highly winter-active genotypes was most sensitive to environmental conditions in winter and spring, while performance of all cultivars and experimental lines was most stable over summer.