Resistance to Sclerotinia Stem Rot in 44 Accessions from Soybean Mini Core Collection

Soybean Sclerotinia stem rot is a fungal disease worldwide caused by Sclerotinia sclerotiorum(Lib.)de Bary.To identify resistant germplasm against S.sclerotiorum for soybean breeding,we evaluated 44 accessions of soybean from the Chinese mini core collection in a two-year field experiment by inoculating four S.sclerotiorum isolates collected from different geographical regions and hosts.The 44 accessions showed different resistance levels to various isolates.Six accessions(13.64%)were moderately resistant,27 accessions(61.36%)were moderately susceptible,9 accessions(20.45%)were susceptible,and the remaining 2 accessions(4.55%)were highly susceptible.No highly resistant germplasm was found indicating that resistant sources to S.sclerotiorum are rare in Chinese soybean mini core collection.Hefeng 24,Datian'edan,Nidinghuameidou,Niumaohuang,Dahuangdou,and Wuyuehuang,which were moderately resistant,were valuable in soybean breeding for S.sclerotiorum resistance.The four S.sclerotiorum isolates had different pathogenicities over accessions and years.Heixi 5 isolated from soybean in Heilongjiang was the most pathogenic with average disease severity index of 49.32 and average lesion length of 5.93 mm.Heirao 24 isolate from soybean in Heilongjiang and Qin 24 isolated from oilseed rape in Qinghai had moderate pathogenicity.Hef 50 isolated from oilseed rape in Anhui showed the weakest pathogenicity with average disease severity index of 39.02 and average lesion length of 3.65 mm.Therefore,isolate Heixi 5 is most effective in identification of resistance to S.sclerotiorum in soybean.