Identification, Molecular Detection And Fungicides Screening Of Pear Major Diseases Pathogens In Four Chinese Provinces

Pear disease is one important factor to restrict the healthy development of pear industry in china. At present, major pear diseases have not been fundamental control, but new pear diseases will be continual emergence. Some secondary diseases may also increase as the main disease. In the manage process, the idea of light prevent and heavy control for pear disease is common. The pathogens infecting pear early was unknown, so grower missed the best time to manage the disease. In the same time, a large number of routine chemicals were used, and many pathogens developed resistance. If we clarify the kinds of pear diseases in the main producing pear area, establish rapid diagnostic pear diseases technology and select new, high efficiency, low toxicity of the fungicides for control pear diseases, it will be significant to Chinese pear industry of healthy development.In order to clarify the major pear diseases in china, distribution of the pear diseases in 10 cities of Jiangsu province, Anhui province, Shanxi province and Xinjiang Uygur Autonomous Region were surveyed from 2007 to 2008. The kinds of pear diseases which we have surveyed were protracted in china map and the map was submitted to http://lsbh.njau.edu.cn. Pear ring rot is the most serious pear disease in Jiangsu province, pear anthracnose has become the first serious disease in Anhui province, and pear Valsa canker is particularly significant in several pear diseases of Shanxi province and Xinjiang Uygur Autonomous Region. Pear black rot general occurs in Jiangsu, Anhui, Shanxi and Xinjiang. The pathogens of pear ring rot, pear powdery milde which infected pear leaves over 60% in partial pear garden was discovered in Pucheng area of Shanxi. Pear anthracnose, pear Valsa canker, pear black rot and pear powdery milde were separated from the pear diseases samples, and the pathogens were identified with morphological and molecular biology methods. The identification results show that the pathogens of pear ring rot, pear anthracnose, pear valsa canker, pear black rot and pear powdery milde were Botryosphaeria berengeriana, Colletotrichum gloeosporioides, Valsa ambiens, Alternaria alternate and Phyllactinia pyri.Based on differences of internal transcribed space (ITS) sequences of Botryosphaeria genus, a pair of species-specific primers Bb1 and Bb2 was designed for detection Botryosphaeria berengeriana. Two pair of species-specific primers E1/E2 and AAF2/AAR3 which are cited from journal reported detected Colletotrichum gloeosporioides and Alternaria alternate respectively. Further use of the three pairs of primers were established for the rapid detection and diagnosis of pear ring rot, pear anthracnose, pear black spot technology that can provide technical services for the production.24 pathogenic fungi species were used to test the specificities of the three pair of primers. PCR amplifications with these primers Bbl/Bb2, E1/E2 and AAF2/AAR3 resulted in products of 326bp,329bp and 340bp from B. berengeriana, C. gloeosporioides, A. alternata genomic DNA respectively. The detection sensitivities of the three pair of primers were lpg, lpg and lOpg. A nested PCR procedure using ITS1/ITS4 as the first-round primers, followed by B. berengeriana primers Bbl/Bb2 increased detection sensitivities at least 105. And, the nested-PCR method could directly detect latent pathogen on the pear tissue. PCR procedure using primers E1/E2 and AAF2/AAR3 could rapid detect pear tissue infected C. gloeosporioides and A. alternate.In laboratory, the toxicity effects of 21 fungicides on Colletotrichum gloeosporioides, Botryosphaeria berengeriana, Alternaria alternate were tested by mycelium growth rate methods. The toxicity result was analysed by the EC50 value. The toxicity of 50% Prochloraz WP was the strongest to Colletotrichum gloeosporioides and Botryosphaeria berengeriana with the EC50 value 0.1195mg/L and 0.0426 mg/L relatively. The toxicity of 50% Iprodione SC was the strongest to Alternaria alternate with the EC50 value 0.6964 mg/L. The toxicity of 50% Prochloraz WP,25% Prochloraz EC,40% Flusilazole EC,25% Azoxystrobin SC,10% Difenoconazole (trade name:Shengshi) WG,10% Difenoconazole (trade name:Score) WG,50% Iprodione SC was all strong to Colletotrichum gloeospor-ioides, Botryosphaeria berengeriana and Alternaria alternate. This experiment provides reference for the chemical control of pear anthracnose, pear ring spot and pear black spot.