连作苹果园土壤真菌的T-RFLP分析

为探讨连作苹果园不同土壤空间真菌群落结构,应用T-RFLP(Terminal Restriction Fragment Length Polymorphism)技术,比较了3个连作园不同取样位置(行间、原穴、株间)和不同土层(0—30 cm、30—60 cm)的土壤真菌多样性,并结合不同样品TRFLP图谱的差异,采用多样性指数分析、聚类分析和主成分分析(PCA),分析了3个连作园土壤真菌群落结构特征。结果表明,磁窑、道朗和金城连作园的土壤真菌多样性存在差异,各采样地区的Shannon多样性指数在0.43—2.47之间,Pielou均匀度指数在0.17—0.85之间,Simpson优势度指数在0.12—0.81之间,Margalef丰富度指数最高的是金城树穴0—30 cm土层(R=4.55),最低的是磁窑行间30—60 cm土层(R=0.77)。在调查的不同取样位置、不同土层中,原树穴具有最高的多样性指数、均匀度指数、丰富度指数和最低的优势度指数;0—30 cm土层的土壤真菌多样性指数、均匀度指数、丰富度指数均高于30—60cm土层,而优势度指数的趋势正好相反;PCA和聚类分析结果显示磁窑、道朗和金城连作园的土壤真菌群落结构均有明显差异,3个连作园的土壤真菌各自构成一个独立的群落结构,这些群落能够适应各自的土壤环境并成为环境的优势群落。

Assessment of fungal diversity in apple replanted orchard soils by T-RFLP analysis

Apple replant disease (ARD) has been reported from all major fruit-growing regions of the world. ARD is a serious problem in about half of old orchard sites surveyed, with typical symptoms including stunted above- and below-ground tree growth, necrosis of feeder roots, water stress and nutrient deficiencies. The etiology of ARD is complex and causal agents vary among different sites and regions. In most sites, biotic factors seem to be prevalent, including nematodes, bacteria, actinomycete, oomycetes and fungi species thought that Pratylenchus penetrans was the primary nematode species involved in ARD. Although several bacterial genera and species have been associated and suggested as being involved in ARD, most bacteria likely impaired plant at inordinately high densities. Evidence for the involvement of actinomycetes in ARD is circumstantial. However, most researches demonstrated fungal and oomycete genera were the main reason for apple replant disease, i.e. fungal genera: Fusarium, Rhizoctonia, Cylindrocarpon; oomycete genera: Phytophthora, Pythium. To investigate the spatial structure of soil fungal community structure in replanted orchards, three replanted orchards in Ciyao, Daolang and Jincheng town were used to take soil samples, which were collected from 0-30 cm and 30-60 cm depth of the row, inter-row and tree hole, respectively. T-RFLP (Terminal Restriction Fragment Length Polymorphism) was applied in the analysis of soil fungal diversity. Based on the T-RFLP pattern differences, diversity index analysis, cluster analysis and principal component analysis (PCA) were combined to do the further analysis of soil fungal diversity from different orchards. The results indicated that soil fungal diversity differed in three orhcards, Shannon diversity index, Pielou evenness index and Simpson index in all samples were between 0.43-2.47, 0.17-0.85 and 0.12-0.81, respectively. The highest Margalef richness index (R=4.55) was observed at 0-30 cm soil layer of tree hole in Jincheng and the lowest value (R=0.77) was obtained at 30-60 cm soil layer of tree inter-row in Ciyao. In all investigated sites and soil layers, original tree hole showed the highest diversity index, evenness index, richness index and the lowest Simpson index. Soil fungal diversity index, evenness index, richness index of 0-30 cm soil layer were higher than those of 30-60 cm soil layer; however, Simpson index expressed a reverse trend. PCA and cluster analysis indicated that soil fungi of Ciyao, Daolang and Jincheng formed independent community structure, respectively, and these communities could adapt to their own specific soil environment and became the dominant population.