Effect Of Biocontrol Bacteria GHt-q6 On Cucumber Root Soil Microecology And Root Knot Nematodes

Cucumber root-knot nematode disease caused by continuous cropping is one of the most serious soilborne diseases,which seriously affects soil quality,soil microbial community structure,quality and yield of cucumber.In recent years,researchers used microbial agents to spread before or after transplanting,which could not only effectively control diseases,contribute to the sustainable and healthy development of agricultural production.In this study,we used high-efficiency mutant bacillus amylogenes GHt-q6 obtained from early screening and mutagenesis of our research group as the material.Field experiment and high-throughput sequencing technology were used to study the colonization of GHt-q6 strain in cucumber,effect on soil microecology of cucumber root system and control effect of cucumber root knot nematode disease.The results provide scientific basis for further research and development of biocontrol agents for cucumber root knot nematodes.The main research results of this experiment are as follows:?1?The mutant strain resistant to 300 g.ml^-1 rifampicin induced by rifampicin was denoted as GHt-q6-Rif,GHt-q6-Rif bacterial suspension was diluted and poured into cucumber root circumference.By colony recovery method,it was found that GHt-q6-Rif could be stably colonized in roots,stems and leaves of cucumber plants after 10 days of inoculation.Root,stem and leaf,the amount of colonization were stable at 4.55×10⁴cfu·g^-1?3.6×10³ cfu·g^-1 and 3.6×10² cfu·g^-1.The amount of colonization was greater in the root than in the stem than in the leaf.?2?Biocontrol bacteria GHt-q6 bacteria suspension after treatment of soil,the first 20 days of bacteria showed a promoting effect,the fungi for inhibition.In the seventh day,The bacterial count was 2.67 times higher of CK,and the fungal count of CK was 2.8 times that of the biocontrol group.The fungal biomass of CK was 2.8 times higher than that of the biocontrol group.After treatment for 20 days,the actinomycetes were significantly inhibited,and the amount of CK actinomycetes at 34 days was 3.38 times that of the biocontrol group.The high-throughput sequencing results showed that after biocontrol bacteria GHt-q6 bacterial suspension was treated with soil,the community diversity of cucumber in the early growth stage did not change significantly,and the diversity of bacterial community in the late growth stage increased.Pseudomonas,Arenimonas,and Lysobacter with biocontrol effects were always the dominant bacteria in the soil.?3?In the first 34 days after treatment,soil sucrase and urease were significantly promoted,and the activity of soil sucrase on the third day was 1.57 times higher than that of CK.The activity was 1.81 times stronger than CK at 7 days after treatment,and the difference between treatments was not significant.During the whole growth period of cucumber,the effect on catalase was less.Biocontrol bacteria GHt-q6 bacterial suspension can effectively promote the increase of soil available P,available K and Organic matter.At the seedling stage,it had the strongest promoting effect on rapidly available phosphorus,which was 1.43 times higher than CK.At seedling stage,it had the strongest effect on the promotion of available potassium,which was 2.17 times higher than CK.In the flowering and fruiting period,the organic matter promotion effect was 1.34 times stronger than CK.?4?Through the detection of nematode population density in root soil at different stages and the investigation on the control effect of cucumber at seedling pulling period,it was found that the control effect of nematode population density in the result period and seedling pulling period was significantly different from that in the blank control group.