| China is the largest producer and consumer of apples in the world, apple planting area and output account are more than40%of the world’s total nunber, which plays an important role in the apple industry. Loess Plateau area is the main planting areas of apple in China, the production of fruit had developed rapidly in recent years, people have become increasingly demanding the quality of fruit. The old varieties were replaced by new varieties, as limited land resources, many old trees were replaced. The apple replanted disease was the major limiting factor. Orchard replanted obstacle is the worldwide problem of fruit development, and to study its mechanism and control technology is also an important part of fruit trees cultivation technology research in. The analysis of different old apple orchards and replant orchards community are the structure of soil fungi in the Loess Plateau area. The specific results gained are summarized as following:1. Sixteen genera of soil fungi were isolated from eighty-four samples (each forty-two) which were collected two times from eight countries of Loess Plateau area. 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 eight countries. The results showed that the amount and species distribution of soil fungi had an obvious variability in different counties. In different areas, the fungi type and quantity and diversity index of the orchard soil are clear by differenct, but the general trend is always that the line of old orchard soil had the highest number of fungal species and the amount. The amount of species and the total number of species and evenness had the lowest in the mass of replanted orchard oil. While there is unconspicuous change between the lines of the old orchard and wheat crop soil fungi in diversity index and evenness change that showed no regular. In the same areas, the line of the old orchard within the soil fungal species diversity index and evenness was significantly higher than the replanted orchard. These results indicate that the fungal community structure is stable within the line of the old orchard because of adaptation and collaboration between each other after years of microbial evolution and other factors to achieve a relatively stable state of equilibrium between the different species of soil fungi. While because of removing of the old trees from the replanted orchard, fungal community structure have been varying degrees of damage, fungal community structure imbalances are likely to be an important factor caused by the apple orchard replantation obstacles.2. Comparative analysis of the eight county soil fungal species composition of law, the results showed that the species percentage of Trichoderma and Gliocladium which had biological control effects in the line of old orchard soil was higher than replant orchard, but the species percentage of Fusarium and Verticillium which had pathogenicity in replant orchard soil was higher than old orchard. This explained that some fungus which had pathogenicity had the relative increasing and some fungus which had biological control effects had the relative reduction in replanted orchard, it showed that this is one of the key factors that caused by continuous cropping obstacles. The Fusarium and Verticillium fungus may be the major pathogens which caused the apple replanted disease in the Loess Plateau area replanted orchards.3. To further validate the reliability of conventional soil fungi separation analysis of the diversity of soil fungal communities, using the PCR-DGGE technology to study the soil fungal community structure from in all42soil samples based on the routine analysis which was acquisited for the second time. Total soil microbial genomic DNA fragment by using of the extraction kit around in the17kb. Amplified by PCR using the primers with a "GC" clamp to obtain amplified fragments is about230bp. At the same place, the soil microbial in the line of old orchard had the most number of bands and in replanted orcharda had the least number of bands. The number of bands of the soil microbial in between the lines of the old orchard and wheat crop had a large fluctuation. We can see from different parts of the apple orchard soil fungal community structure similarity clustering analysis that it is always the same of the structural similarity of the replanted orchard soil fungi and in the line of old orchard soil fungi. This analysis showed that the results of diversity analysis with conventional soil fungi separation had a similar trend.4. Five hundred and thirteen actinomyces isolates of soil samples were also isolated by using the soil plate and dilution plates methods. Using the confrontation culture method, we select21actinomycete strains which have the control effect on the four kinds of pathogenic Fusarium sp.(F. oxysporum, F. proliferatum, F. solani and F. moniliforme) and one actinomycete strains which have the control effect on the four kinds of pathogenic Rhizoctomia solani. The actinomycete strain35-5had the extensive biocontrol effect on the pathogenic fungi. The actinomycete strain which had the better biocontrol effect on the F. proliferatum is the35-7,25-15and18-5; the actinomycete strain which had the better biocontrol effect on the F. moniliforme is the24-6,37-12and35-5; the actinomycete strain which had the better biocontrol effect on the F. oxysporum is the33-8. We have not selected the actinomycete strain which had the better biocontrol effect on the F. solani. The actinomycete strain37-12and24-6had the best biocontrol effect on the R. solani.5. Comprehensive consideration of the various strains of actinomycetes by the inhibitory effect on the tested strains, we choosed the nine strains of soil actinomycetes. Using the methed of growth rate to rescreen the fermentation broth of nine soil actinomycetes antibacterial activity, we discover that the actinomycetes strain37-12antagonistic inhibition of R. solani rate reached95%. The actinomycetes strain37-12antagonistic inhibition of the other tested fungi rate reached50%, so that it had the extensive biocontrol effect on the pathogenic fungi. Followed by the actinomycetes strain24-6, it antagonistic inhibition of the other testing fungi rate reached40%-80%.6. Using16SrDNA sequence analysis methods to sequence the identification of actinomycetes strains24-6and37-12, and then use Balst sequence alignment in GenBank. The results showed that two strains of actinomycetes belong to the Streptomyces sp. |
PDF Full Text Request