Diversity Analysis Of Soil Fungi From Bohai Bay Apple Replanted Orchard And The Screening Of The Antagonistic Fungi

Bohai Bay is the main planting areas of apple in China, the production of fruit was developed rapidly in recent years, people have become increasingly demanding the quality of fruit. The old varieties were replaced of new varieties, as limited land resources, many old trees were replaced. The apple replanted disease was the major limiting factor .The analysis of different old apple orchards and replant orchards community structure of soil fungi in the Bohai Bay.The specific results gained are summarized as following:1. Fifteen genera of soil fungi were isolated from one hundred and eighteen samples which were collected from ten countries of Bohai Bay. The population dominance index, Shannon-Wiener index, evenness, niche breadth and community similarity were used to analyze the diversity and eco-niche of soil fungi in ten countries. The results showed that the amount and species (at generic level) distribution of soil fungi had an obvious variability in different counties. The diversity index and evenness of soil fungi of old orchard were higher than those of replanted orchard, to some extent replant orchard take changes in the quantity of fungi and species composition in the orchard soil.The analysis of the fungal community similarity between different counties showed that the fungal community similarity of soil fungi had an obvious variability and there was an obvious variability between the old orchard and replant orchard of the same county. Further analysis showed that the species percentage of Trichoderma and Gliocladium which had biological control effects in old orchard soil was higher than replant orchard, the species percentage of Fusarium which had pathogenicity in replant orchard soil was higher than old orchard, this showed that Fusarium fungus may be the major pathogens which caused apple replanted disease in the Bohai Bay area replanted orchards.The results of niche breadth analysis indicated that species of Fusarium in old orchards and replanted orchards soil had different niche breadth, the niche breadth of Fusarium was 3.733 in old orchards soil and it was 6.551 in replanted orchards soil, that Fusarium fungi and other harmful microorganisms in the replanted orchards soil had significantly greater competitiveness than that in old orchards soil.2. 58 Fusarium isolates of soil samples were isolated by using the soil plate and dilution plates methods. Using morphology and 5.8S rDNA-ITS sequences analysis, we identified that 58 Fusarium isolates that we selected in this study belonged to 4 Fusariu spp., they were F.oxysporum,F.proliferatum,F.solani and F.moniliforme.The results of pathogenicity showed that F.proliferatum and F.moniliforme had strong pathogenicity. All plants died after inoculation 10 days, and F.oxysporum had low pathogenicity, after 30 days , the tested plants appeared dead leaves, plant death phenomenon ,it deduced that F.proliferatum F.moniliforme and F.oxysporum may be the major fungi of the replanted orchards in the main pathogens of the apple replaneted disease in Bohai Bay.3. The Grey Relational Degree Analysis was employed of 10 Trichoderma isolates which can antagonize to Rhizoctonia spp. and Fusarium spp. They were ananlyed in terms of 8 varying characters including the inhibition rate, growth rate, amount of sporulation, toleration to extreme temperature, pH and toleration to Carbendazim fungicide et al. By this, outstanding Trichoderma isolate T21-1-4 was selected out, followed by T35-2-3 and T16-1-4 Trichoderma isolates.This resoult showed that the integrated characters of those Trichoderma isolates were closed to the ideal Trichoderma isolate, so they were ideal pathogen antagonistic biocontrol strains of Trichoderma spp .The isolate T21-1-4 strongly antagonized Rhizoctonia spp. and Fusarium spp. , had an extensive antagonistic spectrum and could grow well under pH4 and pH10 as well as at 10 and 35℃in the cultural medium containing 0.1 mg/ L of carbendazim.4. Screened T21-1-4,T35-2-3,T16-1-4 Trichoderma strains, useing anti-pot test determined the Biocontrol effect of these Trichoderma strains ,after liquid - solid two-phase fermentation, the results showed that all the treated Begonia seedlings were growing better than CK,which applied T21-1-4 Trichoderma formulations growed best, the average stem diameter, root length and root surface area were the largest,were 0.137 cm,39.10 cm and 6.934 cm~2.It showed that T21-1-4 has good biocontrol effect on the continuous cropping disease, is a better biocontrol strains.5. Using morphological taxonomy and 5.8SrDNA-ITS sequence analysis, we identified that isolate T21-1-4 that we selected in this study was T.harzianum.