山西省玉米大斑病菌生理小种鉴定

Identification of physiological races of Exserohilumturcicumin Shanxi,China

[目的]明确山西玉米种植区大斑病菌生理分化情况,为玉米大斑病的抗病育种、品种的合理布局和综合防治提供理论基础和科学依据。[方法]采用Ht单抗性基因鉴别寄主法,对从山西省14个市县玉米罹病叶片上分离的32个玉米大斑病菌株的生理小种种类、分布和毒力频率进行分析研究。[结果]供试的32个菌株中共鉴定出12个生理小种,分别为0、1、2、3、N、12、2N、3N、12N、13N、23N和123N号。其中,2、12N、13N、23N和123N号生理小种的出现频率之和为65.64%,123N的出现频率最高,占总量的25.00%。山西各玉米种植区的生理小种种类存在明显差异,北部有8种(1、2、N、2N、3N、12N、13N和123N),南部有7种(3、N、12、12N、13N、23N和123N),中部仅5种(0、12、3N、12N和23N)。32个菌株对Ht单基因的毒力频率在56.25%~78.13%之间,对HtN的毒力频率最高,为78.13%;而对含Ht双基因、三基因和四基因组合的毒力频率分别为81.25%、56.25%和25.00%。[结论]山西玉米种植区小种种类和出现频率存在明显差异,表现为北部>南部>中部。在鉴定出的12个生理小种中,12、12N、3N、23N和123N号是山西主要致病小种群体,其中123N为山西的优势小种。单一的Ht抗性基因品种的抗病作用已明显降低,仅依靠这4种Ht单抗性基因的抗病品种已不能有效的防治该病害的发生和危害。

[Objective]In order to provide theoretical and scientific support for the research on the disease resistance breeding,rational distribution of maize cultivars,and comprehensive control of northern corn leaf blight(NCLB),the physiological differentiation,distribution,and virulence frequency of Exserohilum turcicum in Shanxi Province were clarified in this study.[Methods]The physiological races,distribution,and virulence frequency of 32 E.turcicum strains isolated from diseased leaves of corn collected from 14 different districts of Shanxi were analyzed by the differential hosts with the race-specific single Ht resistance genes.[Results]A total of 12 physiological races(0,1,2,3,N,12,2N,3N,12N,13N,23N,and 123N)were identified from the 32 test strains based on the resistant or susceptible reaction of the differential hosts to pathogen.The isolation frequency of five out of 12 races,including 2,12N,13N,23N,and 123N,contributed to 65.64%of the total of tested strains,and the highest isolation frequency was detected for 123N at 25.0%.There were significant differences in term of the types of physiological races among different regions of Shanxi Province.There were eight races(1,2,N,2N,3N,12N,13N,and 123N)detected in the northern regions,seven(3,N,12,12N,13N,23N,and 123N)in the southern regions,and five(0,12,12N,3N,and 23N)in the central regions.The virulence frequencies of tested strains to different Ht genes were between 56.25%and 78.13%with the greatest virulence frequency observed to HtN at 78.13%.The virulence frequencies to the two,three,and four different Ht genes combinations were determined as 81.25%,56.25%,and 25.00%,respectively.[Conclusion]There were significant differences in race types and isolation frequencies in different regions of Shanxi,shown as Northern>Southern>Central.Among the 12 physiological races identified,12,12N,3N,23N,and 123N were the main pathogenic races in Shanxi,of which 123N was the dominant race.It should be of great concern that the resistance of four different Ht genes to E.turcicum has been significantly declined in Shanxi,and the disease-resistant cultivars that mainly rely on mentioned four individual Ht resistance genes have been unable to effectively control the occurrence and damage of NCLB.