Pathogen Identification Of Blackcurrant Leaf Spot And Fungicide Screening

Leaf spot was one of the serious fungal diseases in blackcurrant culture in Heilongjiangprovince. It disserved leaves and formed a lot of light brown spots as soiled on leaves in initialstages, then the spots turned into brown, in the end the spots turned into grey hoar and pycnidiumappeared in the center of the spot, leaves turned yellow and fell off earlier, influenced the outputand quality. Symptom of blackcurrant leaf spot was only recordanced at home and was notresearched detailedly. Pathogen Identification of blackcurrant leaf spot and its biologicalcharacteristics and fungicide screening were studied.Consequently the results would providedtheory basis for breeding of resistance to leaf spot of blackcurrant and its prevention and curecontrol.Diseased samples were collected from Hailin, Huachuan, Binxian and Horticulture stationof Northeast Agriculture University from July to August in 2006. The pathogen was separated bytissue isolation and the biology characters of effects with the aspects of culture medium,temperature, light, pH and humidity were researched. The effective fungicides were chose andscreened by mycelium growth rate means and flat confronting culture means.It was found through observing configuration of mycelium and conidiophore undermicroscope that white, diaphragmatic mycelium extended like branch, and pycnidium was roundor nearly round, and organ wall was dark brown and membranous, and spore was linear,transparent, straight or curving with 1～3 diaphragm. Spore suspension was inoculated to theblackcurrant with 4～5 leaves by the Koch's Postulation and the incipient symptoms appearedafter 3 months. The pathogen was confirmed to belongs to Septoria, Deuteromycetes,Sphaeropsidales, Sphaeropsidales according to《Configuration and taxology of fungus》and《Chinese fungus》.The optimum culture medium was PDA, diameter of colony was 90.0mm under 6d, it hadequable sporulation with 8.55×10~6 ml under 12d. OMA and CMA took the second place,blackcurrant medium agar (BJA) was the worst with 55.0mm under 6d and did not give birth tospore.The temperature range of pathogen growth and spore germination were from 20℃to 30℃,the optimum temperature was 25℃that growth and sporulation were the best and sporegermination percent was 94％under 10h as well as germination percent was 40％and 5％under 24h when temperature was 15℃or exceed 40℃. It was indicated that the pathogen growth was similar under the conditions of all darkness,all light and 12h light-12h darkness (all 90.0mm under 6d). But under 12h, sporulation wasunfavorable under all light that dimeter of colony was 2.87×10~6 ml as well as 4.20×10~6 mlunder 12h light-12h darkness and 8.55×10~6 ml under all darkness. The light was propitious tospore germination that spore germination percent through 2h cultivation were 0,10％,10％underthe conditions of all darkness, all light, 12h light-12h darkness in initial stages as well as sporegermination percent had no effect after 24h cultivation which all exceeded 95％.The pH range from 6.0 to 9.0 had no difference to the growth of pathogen that diameter ofcolony was 90.0mm under 6d, and the optimum pH was 7.0 that growth and sporulation were thebest. Spore germination was better at the range of 5.0～7.0, and the optimum pH was 6.0 thatspore germination percent was 98％under 24h.Spore germination was good under the condition of high humidity, through 24h culture thespore germination percent was 93％under 90％humidity as well as 97％in water, we discoveredthat spore germination percent was 76％under 75％humidity as well as 39％under 60％humidity.The effective chemistry fungicides were Flusilazole (from 1:7000 to 1:10000), Triadimefon(from 1:800 to 1:900), Daotech (from 1:400 to 1:700) and Myclobutanil (from 1:1500 to 1:3000).Effects of restraining to pathogen in Flusilazole was the best that restraining percent was79.3％. In the next place,the better biology fungicides were actinomycetes 2-17 that restraining topathogen percent was 61.9％and validamycin A (from 1:1000 to 1:1600) that restraining topathogen percent was 44.8％. The best chemistry fungicide mix were Triadimefon:Daotech was2:1 that the restraining to pathogen percent was 86.4％, secondly, Flusilazole: Myclobutanil was3:1 that restraining to pathogen percent was 82.8％.