Study On The Biological Characteristics And Resistance Of The Asparagus Stem Blight

Content：The strains isolated from Jiangxi, Hainan, Fujian, Shandong, Hebei, Shanxiprovinces’ asparagus stem blight were identified, analyzed their rDNA-ITS sequences, andbuilt a phylogenetic tree, the result showed that the pathogeny of asparagus stem blight isthe Phomopsis asparagi (Sacc.) Bubak. There are different biological andmolecularbiolog features between several provinces’ strains, the phylogenetic tree put theHainan strains and the Shanxi strains together, the others provinces’ strains be put togetherrespectively, the Hebei strains have extremely difference compared others strains whichITS sequences length are561nt and the others are563nt; The analysis of phylogenetic treebased on neighbor-joining method (NJ) and unweighted pair-group method with arithmeticmeans (UPGMA) revealed that the genetic distance between Phomopsis sp. and Fusariumsp. more shorter than Phoma sp.Researched on sporulation quantity of Phomopsis asparagi(Sacc.)Bubak underdifferent conditions,the results showed that the strain XT1, FJ3and LT1respectively havethe most sporulation quantity on PDA, OMA and NLPDA medium, and the strain FJ5hasthe most sporulation quantity on OLPDA and OLDA medium, On the NLDA, WA andCzapek medium all of the strains has few sporulation quantity. The illumination offluorescent light or black light promoted sporulation. The temperature of the mostquantities’ sporulation was31℃, and sporulation quantity was FJ1>FJ3>XT1on anytemperature except on28℃, when temperature reach34℃none of strain willsporulation.The organicnitrogen can promoted sporulation, but the carbon source have no affection tosporulation. the strain FJ2behaved the strongest virulence and the best inoculationconcentration was1×106spore/mL for virulence identification.The enzyme activity of three kind of cell wall degrading enzymes from Phomopsis asparagi was determined, the result showed the enzyme activity of three kindof wall degrading enzymes include cellulase (Cx), polygalacturonase (PG), Polymethyl-galacturonase (PMG),was dropped off with the prolongation of reaction time. Atthe beginning of the20minutes the enzyme activity rapidly decreased, and slowlydecreased at the succedent time. For the three enzymes, the optimum reaction temperature is60℃, pH value is4.0. And the scale ofenzyme activity is PG>PMG>CxTo define the resistance-level difference of asparagus stem blight fungus from differentprovinces on systemic and protective fungicides, the resistance levels of24isolates from6provinces on carbendazim and mancozeb were determined using the mycelial growth ratemethod,followed with the difference comparison. The results revealed that the resistance ofthe isolates from each province on the two fungicides existed obvious diversity. Theisolates from Shandong Province expressed the most resistance on carbendazim with an average EC50value of1.10mg/L, followed by the isolates from Jiangxi Province andFujian Province, with average EC50values of0.58mg/L and0.33mg/L respectively. Theisolates from Fujian Province expressed the most resistance on mancozeb with an averageEC50value of34.53mg/L, followed by the isolates from Hebei Province and ShandongProvince, with average EC50values of15.88mg/L and14.19mg/L respectively. Comparedto mancozeb it’s easier for carbendazim to produce resistance, with7resistant isolates,3.6575as the resistant level and29.17%as the resistant frequency, while4resistantisolates,1.9017as the resistant level and16.67%as the resistant frequency were includedin mancozeb. Of24isolates SD4existed resistant on both of carbendazim and mancozeb,with resistance levels of10.44and3.01respectively, which expressed multiresistance.