Relationships among alfalfa resistance to Sclerotinia crown and stem rot, <i>Sclerotinia trifoliorum</i> and oxalic acid

Abstract

Sclerotinia crown and stem rot (SCSR) of alfalfa caused by Sclerotinia trifoliorum is one of the main constraints for efficient alfalfa cultivation in temperate climate all over the world. The resistance of 200 alfalfa accessions to Sclerotinia crown and stem rot was evaluated during 2010 to 2011 in the field nursery established in 2009. The resistance of alfalfa accessions germinating seeds to mycelium of Sclerotinia trifoliorum and oxalic acid (OA) concentrations of 10, 20, 30 mM was screened under laboratory conditions. The statistically significant differences at P<0.05 were determined among evaluated alfalfa accessions resistance to all screened factors. The reactions of alfalfa accessions to disease under field conditions showed that majority of the non-adapted accessions were heavily diseased, whereas the resistant accessions had only negligible disease severity. The germination of accessions seeds at oxalic acid concentration of 30 mM showed strong correlation (r = -0.817**, P<0.01) with SCSR severity in 2011. Among OA concentrations, this one showed the highest correlation rate with SCSR as well as was the least time consuming method. This method of seeds germination on mycelium of S. trifoliorum was unfit due to its weak correlation with SCSR and higher inputs.

Keywords: Alfalfa, resistance screening, Sclerotinia trifoliorum, oxalic acid