Isolation And Identification Of Fungi Pathogen From Apple Replant Disease In Bohai Bay Region And The Screening Of The Antagonistic Trichoderma Strains

Bohai Bay is the main planting areas of apple in China. In production，fruit varietiesupdates and the establishment of the new orchard are major problems. The old varieties werereplaced of new varieties, as limited land resources, many trees were replaced. The apple re-planted disease was the major limiting factor.In this paper,we studied the preliminary etiolo-gy of the ARD. The fungi were trapped, separated and identified from the soil; The plant hei-ght, fresh weight and the physical signs was explored with the help of seedlings of Malus hu-pehensis Rehd that by pathogenic fungi. We hope to find the major pathogen of ARD. Usingthe methods Confrontation training and glasshouse culture, we screen out the Trichodermaisolation that has good Bio-control effect to the major pathogen of ARD. The results of the a-bove aspects could be as follows:1、We isolates Fusarium、Verticillium and Rhizoctonia as the Potentially pathogen from118soil samples that collectef from Bohai Bay.341isolates from the soil werepurified.Among the341isolates,129isolates were isolated from the first batch of soil sampleand212isolates were isolated from the second batch of soil sample. After a statistica, wediscover the number of Fusarium in old orchard is more than the number of Fusarium inreplant orchard. We hold the opinion that Fusarium spp. is the major fungi pathogens of theapple replanted disease.2、Using morphology and EF-1α sequences analysis, we identified that341Fusariumisolates that we selected in this study belonged to4Fusariu spp.They were F.oxysporum,F.proliferatum, F.solani and F. verticillioide.3、With the help of seedlings of Malus hupehensis Rehd，we explored the pathogenicityof8Fusarium and1Rhizoctonia（AG4-HG-I）.The result show that F.proliferatum andF.verticillioide had strong pathogenicity. F.proliferatum and F.verticillioide have a significantimpact on The physical signs such as Plant height, Fresh weighe, Leaves area, Length of rootand Number of root of Malus hupehensis Rehd. The physical signs had significant reduction.The isolation32-1-4and1-10-1belonged to F.verticillioide reduced47%and42%plantheight. The isolation1-4-2and1-10-1belonged to F.proliferatum reduced36%and38% plant height. The isolation32-1-4and1-10-1belonged to F.verticillioide reduced the numberof root. Compared with control group the number of root reduced53%and56%.TheRhizoctonia has almost no effect on the physical signs of Malus hupehensis Rehd.Consequently,we think the major fungi pathogens of the apple replanted disease in Bohai Bayare F.verticillioide F.proliferatum and F.oxysporum.4、We screen out the Trichoderma isolation2-15-5that has good Bio-control effect to themajor pathogen of ARD with the help of anti-pot test and glasshouse culture. In anti-pot test,Trichoderma2-15-5had good effect on F.verticillioide and F.proliferatum. The inhibition rateof the two pathogens are75.32%and70.83%. The seedlings of Malus hupehensis Rehdwhich inoculate Trichoderma2-15-5fermentation had almost no difference with the blankcontrol. Compared with the control that inoculate pathogen, the Plant height, Fresh weighe,Leaves area of seedlings of Malus hupehensis Rehd increased79%,81%and78%. The resultshowed Trichoderma isolation2-15-5is a better biocontrol strains.