Variation in Waterlogging Response among Ecotypes of Trifolium Subterraneum Ssp. Yanninicum and Their Relationships with Site of Origin

Background and AimsIn the annual pasture legume Trifolium subterraneum , ssp. yanninicum exhibits higher waterlogging tolerance than ssp. brachycalycinum and ssp. subterraneum . This study investigates waterlogging tolerance within ssp. yanninicum ecotypes and explores correlations with seedling phenotypic traits and site of origin eco-geographic variables.MethodsTwenty eight diverse ssp. yanninicum ecotypes collected from the Mediterranean region and four cultivars were grown in a controlled environment glasshouse. After 14 days of growth seedling traits were measured. After 21 days of growth, free-drained (control) and waterlogged treatments were imposed for 28 days. Eco-geographic variables were generated from ‘WorldClim’ using collection site locations.ResultsUnder waterlogging, shoot relative growth rate (RGR) ranged from 87–108% and root RGR ranged from 80–116% of controls. Waterlogging reduced shoot dry weight (DW) in four of 32 genotypes, while root DW was reduced in 13 genotypes. Leaf size was maintained, or even increased, under waterlogging in 31 genotypes. However, petiole length was more affected by waterlogging and has value as a waterlogging tolerance indicator. Waterlogging tolerance was not significantly correlated with seedling DW, flowering time or precipitation at the site of origin, while shoot growth under waterlogging had a positive correlation with summer temperatures at origin.ConclusionsGenotypes of ssp. yanninicum tolerated transient waterlogging and greater tolerance was observed among ecotypes, rather than cultivars. An easy-to-measure indicator of tolerance was found in petiole length reduction. This study highlights untapped genotypic variability for breeders to improve the productivity and persistence of ssp. yanninicum under waterlogging.