Molecular Mechanism Of Soybean In Response To Fusarium Solani

Fusarium solani（F.solani）,the causal agent of sudden death syndrome（SDS）is an important soybean disease of recent times.SDS of soybean is a complex root rot disease caused by the semi-biotrophic fungus F.solani and a leaf scorch disease caused by toxins produce by pathogen in the roots.Crop rotation is not an effective management strategy,since the pathogen may survive long periods in the soil or may infect or be sustained on weeds or crops other than soybean.The pathogens are often found together in soybean（Glycine max（L.）Merr.）fields.This study was conducted to compare the resistance response between two soybean cultivars,the significant role of salicylic acid during disease response and the effect of exogenously spraying soybean seedlings with salicylic acid.Eighteen soybean cultivars were used for screening against SDS using greenhouse screening procedures.Results from several screening procedures showed Jiuyuehuang as susceptible and Nadou12 as resistant cultivars.Molecular,physiological and biochemical analysis were conducted to evaluate the resistance responses,functions of salicylic acid and effect of exogenous SA application.Results from the study showed that histochemical analysis with DAB and Trypan blue staining’s indicated an accumulation of reactive oxygen species（ROS）and cell death in surrounding area of SDS which was higher in susceptible cultivar than in resistant cultivar.A biochemical study revealed that the activities of superoxide dismutase（SOD）,peroxidase（POD）,enzymes involved in scavenging ROS,was increased in susceptible cultivar after SDS infection.However,catalase（CAT）decreased in the susceptible cultivar and increased in the resistant cultivar after infection.In addition,hydrogen peroxide（H₂O₂）and malondialdehyde（MDA）content also increase in the susceptible cultivar than in resistant cultivar.HPLC analysis indicated that free and total SA content increased in the susceptible cultivar than in resistant cultivar.In addition,exogenous SA application also induced some level of resistance to F.solani by the susceptible cultivar through increased levels of Pathogenesis related（PR）genes,increased levels in enzymatic activities and increased level of endogenous SA level at 3dpi with F.solani.Our in vitro antifungal study showed that SA mycelia growth of F.solani was not significantly affected by SA amendment of potato dextrose agar（PDA）medium.In addition,a real quantitative PCR analysis showed an accumulation of pathogen related（PR）genes in the resistant cultivar than in susceptible cultivar.Results from the current study provided:（i）a novel insights between soybean and F.solani interaction by explaining the resistance mechanisms involved during fungal infection;（ii）showed that increase level in endogenous SA increases disease resistance;（iii）showed that exogenous SA application can induce resistance to pathogen infection in soybean.