Physiological Races,Mating Type Monitoring And Genetic Diversity Of Setosphaeria Turcica In Maize Of Heilongjiang Province

Northern Corn Leaf Blight is one of the main leaf diseases with a wide distribution and serious harm to maize production in the world.And it is also one of the most serious diseases in the maize production of Heilongjiang Province,China.The disease can cause a significant reduction in maize production and bring about huge economic losses during the epidemic.Due to abnormal changes in environmental conditions,exist miscellaneous varieties and change frequently,have the large amount pathogens in the field with corn succession cropping etc.,physiological races of Setosphaeria turcica is becoming increasingly complex in recent years in Heilongjiang Province.Therefore,we should systematically analyze composition,frequency and changed trend of physiological races,composition and distribution of the mating type,the genetic background of the physiological races in different maize production area of Heilongjiang Province.This research result will be of great practical guidance to the risk assessment of the occurrence of Northern Corn Leaf Blight,the rational distribution of maize varieties,and selection and breeding of disease-resistant varieties.In this experiment,a total of 206 Setosphaeria turcica strains were isolated from different geographical regions of Heilongjiang Province for identification of physiological races by the conventional single gene(Ht gene)identification technique in 2016 and 2017.The results show that the race 0,1,2,12,123,N and 23 N were found from the 106 strains collected from 31 sampling points of 9 urban areas in Heilongjiang province in 2016.And,the race 0 and 1 were the dominant races with 36.8% and 34.9% of the total,respectively;In 2017,the race 0,1,2,3,12,13,23,123,N,1N,12 N and 3N were found from the 100 strains collected from 32 sampling points of 8 urban areas in Heilongjiang province.And,the race 0 and 1 were still the dominant races with 41% and 14% of the total,respectively.But,the percentage of race 1 has declined dramatically in 2017.The main race is number 0 at the rate of 41% which distributed in all 8 urban areas.Compared with 2016,more races(race 3,13,23,1N,12 N and 3N)were found in 2017.Through the two-years’ identification,race 0 and 1 are the predominant race of Setosphaeria turcica in Heilongjiang.And composition of physiological races of Setosphaeria turcica in Heilongjian Province tends to be complicated.The mating type of Setosphaeria turcica strains isolated from different geographical regions of Heilongjiang Province in 2016 and 2017 was determined:88 of the 106 strains were a mating type,14 were Aa mating type and 4 were A,which accounted for 83%,13.2%,and 11.6% of the total,respectively.And no neutral strains were found;In 2017,43 of the 60 strains were a mating type,10 were Aa mating type,and 7 were A mating type,which accounted for 71.7%,16.7% and 11.6% of the total,respectively.From two-year data,a mating type is the dominant mating type of Setosphaeria turcica in Heilongjiang Province.But the proportion of Aa mating type has shown a rising trend recently.Simple Sequence Repeats(SSR)analysis was used to evaluate genetic diversity of 60 single spore isolates of Setosphaeria Turcica collected from different maize growing areas of Heilongjiang Province.SSR analysis using 5 SSR primers resulted in 45 reproducible bands with 2 to 15 bands/each primer.On average,each primer amplifies to 9 bands.With the similarity coefficient of 0.91 as the boundary,cluster analysis separated the isolates into 9 groups.Analysis of molecular variance showed that a significant correlation was found between SSR groups and mating type.And no significant correlation was found with physiological races and geographical location of isolation.There was moderate genetic differentiation associated with the variation of populations and geographical location of the isolates,and 93.39% was attributed to within the population.There was little genetic differentiation associated with the variation of populations and physiological races of the isolates,and 99.80% was attributed to within the population.And there was moderate genetic differentiation associated with the variation of populations and mating types of the isolates,and 85.32% was attributed to within the population.These results indicate that Setosphaeria turcica populations infecting maize is complicated and has rich genetic diversity in Heilongjian Province.