| Continuous cropping obstacles will lead to slow growth and severe disease of apple plants,deterioration of soil physical and chemical properties and the reduction of production of orchards.To relieve apple continuous cropping obstacle effeciently,this study gathered apple orchard soil samples from shandong yantai,screened athogenic bacteria,siderophores produced bacteria and phlorizin degradation bacteria and identified the strains.Verified the effects of several strains to catalyse the apple stock Malus hupehensis with pot experiment.The study got 13 growth-promoting strains from apple rhizoshpere.There are 3 antagonistic bacterias and they are Bacillus methylotrophicus PQ11 and PA19,Paenibacillus polymyxa PY7.There are 7 strains with high siderophores production and they are Bacillus methylotrophicus GEN11 and GEN12,Alcaligenes faecalis PJ3 and PK48,Bacillus siamensis PE4,Pseudomonas chlororaphis PD1,Serratia nematodiphila PJ6.There are 4 phlorizin degrading bacteria strains and they are Pseudomonas chlororaphis PD1,Bacillus aryabhattai PD4,Pseudomonas mediterranea PD14,Serratia nematodiphila PK50.This provided bacterial resources for apple-specific microbial fertilizer.The study verified the effects of Paenibacillus polymyxa PY7,Bacillus methylotrophicus FKM10,Enterobacter ludwigii KD49 on Malus hupehensis through pot assay.The results showed as follow:(1)Compared with CK group,the plant height,stem diameter,leaf number of Malus hupehensis of treated groups began to show the advantage from 50 days after irrigation with strains.The plant height and stem diameter Malus hupehensis of FKM10 treatment had significant differences respectively in 50-90d、70-90 d.The plant height,stem diameter,leaf number of Malus hupehensis of PY7 treatmnet had significant differences respectively in 50-90 days,50-110 days,50-70 days.While that of KD49 treatment had significant differences respectively in 50-70 days,50-90 days,50-70 days.The fresh weight of total plant,aerial part and underground part of treated groups were all higher than that of CK group and PY7 had most evident effects on plant fresh weight.The dry weight of root,stem and leaves of three treated groups were all higher than that of CK group and the dry weight of root and stem of KD49 treatment had significant advantages,while PY7 treatment group had significant advantage in dry weight of stem.Bacillus methylotrophicus FKM10 had no obvious effect on plant potassium accumulation while FKM10 could improve the content of phosphorus and nitrogen in root and leaf.Paenibacillus polymyxa PY7 could improved the potassium content in root,leaf and plant while PY7 didn’t show obvious effect on the accumulation of nitrogen and phosphorus.Enterobacter ludwigii KD49 could significantly increase the content of plant total phosphorus and increase the nitrogen accumulation of Malus hupehensis stem.But KD49 didn’t show obvious effect on the potassium accumulation.(2)Compared with CK group,the treated groups could improve the SOD and POD enzyme activity and induce the system resistance of Malus hupehensis in different degree.In 2d,30 d,75d,90 d after irrigating,the SOD,POD enzyme activity of FKM10 treatment were significantly higher than CK.KD49,PY7 could improve the activity of SOD and POD in a certain period after treating.Of the three bacterias,FKM10 had the most significant influence on plant defense related enzyme activity.(3)Compared with CK,the soil phosphatase,urease and sucrase activities were improved in different degree in groups treated with strains.And this three enzyme activities of FKM10 treatment and PY7 treatment were higher than KD49 treatment.Meanwhile,3 strains reduced the activity of soil catalase,FKM10 treatment and PY7 treatment had significant difference with CK group.The soil available phosphorus,available nitrogen content of FKM10 treatment is lower than that of CK group while the available potassium content is higher than that of CK group.The soil avilable phosphorus and available potassium content in PY7 group were lower than that in CK group and the available nitrogen content was lower than that of CK group.The soil available phosphorus,available nitrogen and available potassium content in KD49 group were all reduced compared with CK group.Maybe the growth-promoting strains accelerate the Malus hupehensis absorbtion of nutrient and resulted in the reduction of soil available nutrient.(4)The apple rhizosphere bacterial and fungal community structure were measured with Illumina Miseq method.The soil bacterial diversity and richness of FKM10 treatment,PY7 treatment,KD49 treatment were superior to CK group and the soil fungal diversity and richness were inferior to CK group.The bacterial abundance of PY7 treatment and KD49 treatment were superior to FKM10 group while bacterial diversity of PY7 treatment and KD49 treatment were slightly lower than FKM10 treatment.PY7 showed the most significant influence on the reduction of soil fungal diversity and abundance and the following was KD49,and the effect of FKM10 was slightly poorer.The strains could cause the increase of bacterial quantity and variety and lead to the reduction of soil fungal quantity and variety.And this may has important role in the control of continuous cropping obstacle.Compared with CK group,FKM10 treatment had 10 bacterial genus with significant difference in relative abundance,1 specific genera,8 genus with significant increase and 1 genera with significant reduction.Meanwhile FKM10 treatment had 6 fungal genus with significant increase,5 genus with significant reduction.PY7 treatment had 16 bacterial genus with significant increase and there were 4 specific genus of them,6 fungal genus with significant increase and 5 fungal genus with significantly reduction.KD49 treatment had 8 bacterial genus with significant difference in relative abundance,2 specific genus,6 genus with significantly increase.Meanwhile KD49 treatment had 3 fungal genus with significantly increase and 3 fungal genus with significantly reduction.Among the three strains,PY7 and FKM10 showed more obvious impact on the community structure of soil.The increase of relative abundance of Rhodobacter and some other generas may have beneficial effect on the soil material transformation,increase of soil organic matter and the degradation of poisonous material.The decrease of pathogenic fungal genus or harmful fungal genus like Fusarium,Ilyonectria,Lecanicillium,Ramichloridium and the increase of beneficial fungus like Nectria,Monacrosporium may play role in reducing quantity of pathogenic microorganism,improving the disease resistance of plant,reducing the amount of root-knot nematodes and so on.This study screened several beneficial strains from apple rhizosphere,enriched the apple rhizospheric bacterias and provided resources for apple-specific microbial fertilizer.The pot experiment results show that: All the three strains can significantly improve apple rhizosphere environment,increase the abundance of bacterias and the beneficial bacterial and fungi generas especially,reduce the abundance of apple pathogens,promote plant growth,inducing plant systemic resistance and Paenibacillus polymyxa PY7 and Bacillus methylotrophicus FKM10 were superior to Enterobacter ludwigii KD49.These strains have important application value in alleviating apple continuous cropping obstacle,control soil borne disease and promote the growth of apple. |
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