Analysis Of The Resistence Of Soybean Cultivars From Huanghuai Region To Phytophthora Root Rot

Phytophthora root rot,incited by Phytophthora sojae,is a destructive disease of soy bean,and has been reported in the Huanghuai region,and it has a trend of expansion in this region.Using resistant cultivars to control the disease is the most economical and effective measure.The aim of this paper was to screen effective resistance sources to P.sojae for controlling disease.In this paper,80 soybean cultivars or lines from Huanghuai region in China were evaluated for their responses to 8 strains of P.sojae using the hypocotyl mycelium block inoculation technique.80 soybean cultivars or lines from Huanghuai region were identified having high resistance to Racel,Race3,Race5 strains and having some resistance to Race4,USAR2,Ps41-1,PsMC1 strains,while the resistance to PsJS2 strain was low.There are some soybean cultivars had resistance to each P.sojae strain,and 80 cultivars were identified having resistance to 2-8 strains of the pathogen.80 cultivars was elicited 62 different reaction types with by the 8 strains of the pathogen,and reaction types among different cultivars but from the same region were quite different.These results showed that the soybean cultivars from Huanghuai region had abundant resistance diversity to P.sojae and there was a variety of cultivars could be used to control this disease.Soybean root rot is one of the main factors that caused the loss of soybean production in China,plenty of pathogens could cause soybean root rot singly or compoundedly.Our laboratory had isolated and identified the samples which collected from Huanghuai region in 2014,and the results showed that the compound infection was widespread in soybean root rot,while both detection rate of Fusarium and P.sojae were high.Therefore,this test was to investigate the two pathogens influence on soybean resistance.Disease symptom of soybean seedlings compound inoculated with P.sojae and Fusarium,compared with singly inoculated with P.sojae or Fusarium,the incidence variation type of soybean seedlings compound inoculated with the two pathogens included aggravation,alleviation and invariability,and there were differences in the proportion among different combinations of the two pathogens.Soybean seedlings inoculated with the two pathogens compared with singly inoculated with P.sojae,the incidence variation type of aggravation,alleviation and invariability were 41%,44%and 15%,respectively,while compared with only inoculated with Fusarium,the incidence variation of aggravation,alleviation and invariability were 49%,34%and 17%,respectively.Disease symptom of soybean seedlings compound inoculated with P,sojae and Fusarium,compared with only inoculated with P.sojae or Fusarium,aggravation and incidence changing(including aggravation and alleviation)accounted for 65.52%and 95.86%of all compound inoculation number,respectively.The findings indicate that the effects of the compound infection between two pathogens on soybean root rot are varied,but the main effects is the host’s resistance loss or decreasing,or pathogenicity of the two pathogens enhanced.