Research On The Effect Of Apple And Pear Crop Rotation On The Plant

In the production of old apple and pear orchards,when renewing and rebuilding,there is a phenomenon that the growth of the plant is inhibited by the change of crop planting.In this study,we investigated the effect of the original soil environment on the plants after replanting apples and pears in pots,and further determined the effect of the major phenolic acids and pathogenic fungi of apples and pears on the seedlings of Pyrus betulifolia Bunge.seedlings and Malus hupehensis Rehd.seedlings under greenhouse conditions,with the following main results:1、Older pear orchard soils significantly inhibit the growth of Malus hupehensis Rehd.seedlings.Compared to Malus hupehensis Rehd.seedlings planted in pear fumigated soil,Malus hupehensis Rehd.seedlings planted in old apple orchard soil had 20%,19%,28% and26% lower height,ground diameter,fresh weight and dry weight,respectively.Root activity,root length,root surface area,root volume and root tip number were significantly reduced by48%,44%,18%,27%,and 63%,respectively;the activities of POD,CAT,and SOD enzymes were significantly reduced by 32%,42%,and 71%,and increased the MDA content in the root system by 66%.2、Older apple orchard soils significantly inhibited the growth of Pyrus betulifolia Bunge.seedlings.Compared to Pyrus betulifolia Bunge.seedlings planted in apple fumigated soil,Pyrus betulifolia Bunge.seedlings planted in old apple orchard soil had 40%,25%,41% and46% lower height,ground diameter,fresh weight and dry weight,respectively.Root activity,root length,root surface area,root volume and root tip number were significantly reduced by75%,21%,7.3%,50% and 17%,respectively;root SOD,POD and CAT activity were significantly reduced by 51%,50% and 60%,and increased the MDA content in the root system by 150%.3、After apple and pear crop change planting,the number of bacteria in old apple orchard soil was significantly lower,the number of fungi was significantly higher,the ratio of bacteria to fungi was lower,and the activity of major soil enzymes was lower.The number of bacteria in the old apple orchard soil decreased by 20%,the number of fungi increased by 78%,and the activities of urease,sucrase,phosphatase,and catalase decreased by 21%,15%,6%,and34%,respectively.4、After apple and pear crop change planting,the number of bacteria and the number of fungi in the soil of old pear orchard were significantly lowered and the ratio of bacteria to fungi was reduced,and the main soil enzyme activities were lowered.The number of soil bacteria in old pear orchards was reduced by 38% for bacteria,28% for fungi,and 8%,14%,13% and 9% for urease,sucrase,phosphatase and catalase activities,respectively.5、The measured concentrations of the three phenolic acids in the soil of the old apple orchard and their mixture would have an inhibitory effect on the growth of the Pyrus betulifolia Bunge.seedlings.The dry weight and fresh weight of Pyrus betulifolia Bunge.seedlings were 78% and 63% of the control group(CK),respectively.The inhibitory strength of different phenolic acids on root SOD activity in descending order was: mixed phenolic acid > cinnamic acid > phlorizin > vanillic acid;The inhibition intensity of POD activity in descending order was: mixed phenolic acid > cinnamic acid > phlorizin > vanillic acid;the inhibition intensity of CAT activity in descending order was: mixed phenolic acid > cinnamic acid = Phlorizin > vanillic acid;the MDA content in descending order was: mixed phenolic acid > vanillic acid = cinnamic acid > phlorizin.6、The measured concentrations of the two phenolic acids in the soil of the old pear orchard and their mixture inhibited the growth of Malus hupehensis Rehd.seedlings.The dry weight and fresh weight of Malus hupehensis Rehd.seedlings were 57% and 61% of the control(CK),respectively.The inhibition intensity of different phenolic acids on root SOD and POD activities in descending order were: mixed phenolic acids > phthalic acid > benzoic acid;CAT activity inhibition intensity in descending order were: mixed phenolic acids >phthalic acid = benzoic acid;MDA content in descending order were: mixed phenolic acids >benzoic acid > phthalic acid.7、The greenhouse pathogenicity test showed that the main pathogenic Fusarium species Fusarium oxysporum,Fusarium solani,Fusarium proliferatum,Fusarium moniliforme in apple crop orchards were all highly pathogenic to Pyrus betulifolia Bunge.seedlings.Through the isolation and verification of the pathogenic fungus in the soil of pear orchard,it was proved that the two fungal strains(Fusarium incarnatum and Alternaria alstroemeriae)were pathogenic to pear and would also be strongly pathogenic to the seedlings of Malus hupehensis Rehd.,causing the death of Malus hupehensis Rehd.seedlings.