| Potato Verticillium wilt,a kind of typical soilborne diseases caused by Verticillium species,can lead to great losses in yield and quality,wilt and dead of potato plants,therefore threaten potato production.Since 2015,as potato becoming one of main food,Verticillium wilt increasingly serious in some areas with the planted area expansion and continuous cropping of potato.In China,the pathogen type of Verticillium wilt in potato is not clear.In order to identity type of Verticillium species,dominant species,distribution patterns,host range of the pathogens,we carried out a systematic study on the etiological of samples with symptomatic potato plants collected from Qinghai,Ningxia,Mongolia,Gansu and Shaanxi province,and evaluated the resistance of the main potato cultivars to potato Verticillium wilt,and screened out varieties with different resistance to Verticillium wilt,providing theoretical guidance for the rational use of potato varieties.The mainly results of this study as following:1.Two hundred and eighty-seven samples of symptomatic potato plants were collected from 15 counties in five provinces from Northern China including Qinghai,Ningxia,Mongolia,Gansu and Shaanxi,187 Verticillium-like colonies were isolated from these samples,all isolates were identified as Verticillium dahliae and V.nonalfalfae,combining Koch’s syndrome identification and analysis of multigene phylogeny based on the partial sequences of actin(ACT),elongation factor 1-alpha(EF1α),glyceraldehyde-3-phosphate dehydrogenase(GPD)and tryptophan synthase(TS)genes.One hundred and fifteen isolates comprising 61.5% of the total were identified as V.dahliae,which is the dominant species,and the remaining 38.5% of the isolates were identified as V.nonalfalfae.V.dahliae was widely distributed in Shaanxi(84.1%),Inner Mongolia(76.7%),Gansu(12.8%)and Qinghai(100.0%,representing a single isolate).V.dahliae was not recovered from the samples in Ningxia.V.nonalfalfae was recovered from Shaanxi(15.9%)and Inner Mongolia(23.3%)at lower frequencies,and dominated the collections from Gansu(87.2%)and Ningxia(100%).V.dahliae was distributed production fields located primarily at altitudes below 1800 m.However,V.nonalfalfae was the primary causal agent in fields located above 1800 m.Pathogenicity test showed that both V.dahliae and V.nonalfalfae can infect potato seedlings and cause typical symptoms of Verticillium wilt,in addition,the disease severity caused by each of the V.dahliae isolates was higher than that caused by V.nonalfalfae.There are no differences in pathogenicity among V.nonalfalfae isolates.2.The results of biological characteristics showed that the optimum temperature for the colony growth of V.dahliae was higher than that for V.nonalfalfae.The optimum temperature for the colony growth of V.dahliae was 25°C;the optimal pathogenicity temperature range from 25 to 30°C.The optimum temperature for the colony growth of V.nonalfalfae strains was 20°C;the optimal pathogenicity temperature was 25°C.The pathogenicity test of V.nonalfalfae to 13 dicotyledonous crops of 6 families including Solanaceae,Asteraceae,Leguminosae,Cruciferae,Cucurbitaceae,Malvaceae and showed that V.nonalfalfae exhibiting high pathogenicity to summer squash,cucumber,eggplant,tobacco,cowpea,cotton and sunflower,and showing moderate pathogenicity to tomato,pepper,lettuce,and cabbage.However,V.nonalfalfae has no pathogenicity to broccoli and lucerne.3.The results of resistance assessment of 30 potato cultivars to Verticillium wilt showed that Zhongshu 20,Z2011-1,Zhongshu 19,Hongyun,Longshu 8,Qingshu 9,Zhongshu 21,Zhongshu 18,Longshu 13,L0227-18,and Longshu 11 were resistant to V.dahliae.Among them,Qingshu 9,Zhongshu 18,Longshu 8 and Zhongshu 19 had higher resistance than others cultivars to V.dahliae.Helan 15,Longshu 6 and Zaodabai were highly susceptible to V.dahliae.Nine of the 30 cultivars were selected and tested for their resistance to V.nonalfalfae.The resistance of these cultivars was roughly accordance with that to V.dahliae,whereas,Longshu 11 identified as resistant to V.dahliae was susceptible to V.nonalfalfae. |
