Occurrence,etiology Of Ditylenchus Destructor And Evaluation Of Cultiva Resistance In Dingxi Of Gansu

Ditylenchus destructor, caused serious economic losses, is an important disease of potato storage period and an important global quarantine pests. This study researched the occurrence and damage, species identification, culture conditions, regularity of infection and resistance evaluation of D. destructor in Dingxi of Gansu, the main results are as follows:1 The symptoms of D. destructor on potato were observed and described in this paper. And the occurrences of this disease in Dingxi of Gansu were investigated by the method of random sampling. The results of investigation showed that the incidences of D. destructor on potato were 2-11% and disease index were 0.72-5.33. The disease degrees displayed big differences among different potato varieties and Qingshu 9 and Netherlands 15 were more susceptible to D. destructor than other varieties investigated.2 Four nematode populations isolated from potatoes were identified based on morphological and molecular methods, UPGMA method was used to draw the phylogenetic tree of nematode community of ITS sequence, and pathogenicity was tested according to Koch’s Rule. The result showed that morphological features of the four populations were consistent with D. destructor in morphology, and the population DX27 was slight difference with other three populations. The amplified products of r DNA-ITS using the universal primers TW81/AB28 were 915 bp. The results of sequence analysis showed that only 25 sites are difference in ITS1 region betwen DX27 and other three populations. Phylogenetic tree showed that the population DX27 and the haplotype C were in the same cluster, the population DX11, population DX16, population DX19 and the haplotype B were in the same cluster. Based on morphological characteristics and r DNA-ITS sequence analysis, the pathogenic nematodes was identified as D. destructor, the population DX27 can be grouped into haplotype C and other three populations can be grouped into haplotype B.3. To get the optimal culture conditions, D. destructor was cultured on F. solani, F. Verticillium, F. oxysporum, F. semitectum, B. cinerea, T. longibrachiatum, A. alternate and A. solani in 15 ℃, 20 ℃, 25 ℃ and 30 ℃ to maintain. The results showed that the amount of nematodes cultured on F. solani, F. Verticillium and F. semitectum were extremely significant difference compared with other three species. And the best fungus to culture D. destructor is F. solani,the number of nematodes and the magnification were 112667 and 113 times. The optimum temperature to culture D. destructor was 25℃, 20℃, 30℃ and 15℃ respectively for most fungus besides B. Cinerea. And the optimum temperature for B. Cinerea was 20℃.4.The infection pattern of D. destructor in potato was studied by using the method of quantitative inoculating nematodes to soil. The results showed that the D. destructor can infected potato stem and root, and mainly infected the parts of mother tuber, stolons and new tubers. At the early stage of the potato growth(75 d ago), the D.destructor mainly infected mother tubers. At the stage of forming the potato stolons(75-90 d), the nematodes began to spread from mother tubers to stolons. After this, with the formation of new tubers(after 90d), the nematodes began to spread from stolons to new tubers, and the harm gradually increased with the growth of new tubers. The infection situations of D.destructor in the different inoculation period was also determined. The results showed that the infection of D.destructor was gradually reduce with the delay of inoculation time, the earlier the inoculation time of nematodes, the more serious the harm to potatoes. The time after planting 70 days was the forming stage of stolons and new potatoes, this period was the best time of D.destructor’s infection, and the harm was most serious.5. The resistances of 14 potato varieties from Dingxi of Gansu were evaluated by the method of artificial inoculation tests in laboratory. The resistance evaluation showed that Kexin 1 and Longshu 6 were resistant varieties, but Qingshu 9, Atlantic, Xindaping, Shepody and Netherlands 15 were susceptible varieties.