Study On The Diversity Of Nematodes And Microorganism In Rhizosphere Soil Of Different Age Apples

In recent years,the fruit tree industry in China has developed rapidly.The speed of replacement of various varieties of apple has accelerated,which lead to continuous cropping problems increasingly prominent,such as poor seedling growth are exhibited.Apple replantation in major apple producing areas has become apparent and has severely affected the development of the fruit tree industry.In this paper,we chose the rhizosphere soil of apple orchards in Shijiazhuang,Hebei Province as the research object.The nematodes and microorganisms in apple rhizosphere soils were isolated and identified through sucrose centrifugation and series dilution of soil concentration methods.In addition,the differences of biodiversity and community structure of nematodes and microorganisms in rhizosphere soils between different apple tree ages or different periods were compared.The results revealed the distribution rule of nematodes and microorganisms in rhizosphere soils for apple orchards of different tree years which can provide scientific theoretical supports for the apple replant and the environmental problems of rhizosphere soil in apple orchards.The main results are as follows: 1.Biodiversity of nematodes in rhizosphere soils for apple trees of different ages1)The predominant communities of nematodes in the rhizosphere soils of 5-year-age and 23-year-age apple trees were Bacterivorous nematodes,Plant-parasite nematodes,Fungi nematodes,and Omnivores-predator nematodes.And Eucephalobus,Rhabditis and Acrobeloides are dominant genuses.2)The total numbers and relative abundance of nematodes in the rhizospheric soils of 23-year-age apple trees were higher than those at 5-year-age;the nematode diversity and evenness indices in the rhizospheric soils at the age of 5-year-age were higher than those in the 23-year-age.The rhizosphere soil nematode density of 5-year-age and the 23-year-age apple trees was direct proportional to the month.3)The quantity of soil nematodes in the 5-year-age and 23-year-age rhizosphere concentrated in 0-20 cm soil layer,but the soil nematode species in 20-40 cm soil layer were richer than those in 0-20 cm.2.Rhizosphere soil microbial diversity for apple trees of different ages1)Among the apple rhizosphere soils of different ages,actinomycetes accounted for the most(68%,55%,48%),followed by bacterium(31%,43%,49%)and fungi were least(1%,2%,3%).The total microbial numbers in rhizosphere soils decreased with the increase of apple tree ages.The numbers of isolated actinomycetes decreased with the increase of apple tree ages.However,the numbers of isolated bacterium and fungi increased with the increase of apple tree ages.2)The correlation between the microbial quantity in apple rhizosphere soils and the apple tree age was significant,which was most obviously at a level of 0.05.3)In April to July,the numbers of bacterium and actinomycetes presented a shape of "W" in the rhizosphere soil of 14-year-age and 23-year-age apple trees.However,the numbers of fungi in the rhizosphere soil of 14-year-age and 23-year-age apple trees showed little change during April to July.