| With the rapid development of facility agriculture,soilless culture and plug seedling production have been widely applied,accelerating the development of solid cultivation substrates,however,the quality of the imported substrate was higher than the domestic peat substrate,thus,it is particularly urgent to enhance the overall level of domestic breeding substrates.Our laboratory has previously developed different biological seedling substrates with single functional microbe.In order to further enhance the mutifunction of the biological substrate,in this study,microbes with one or more functions of dissolving phosphorus,producing auxin antagonistic pathogens and so on isolated from the plants rhizosphere were screened for microbial groups constration.After getting multifunctional microbial groups,bio-nursery substrates containing these grops were developed.Finally,the growth promoting effect of bio-nursery substrates and the subsequently pot experiments to evaluate the effect of seedlings from the bio-nursery substrates after transplanting were performed.The main results obtained are listed as follows:1.Abilities of producing IAA or solubilizing phosphorus of microbes previously isolated were were compared and growth promoting effects of bio-nursery substrates produced by these strains on the seedling growth were evaluated.Results showed 10 strains can produce IAA,and 5 of them(strains L-60,NJAU-5,69,84 and 57)can produce more than 5 mg·L-1 of IAA.Five strains inculding NJAU-3,L2,L8,Y2 and Y40 have obvious halo(D/d values greater than 1.5)on NBRIP medium with Ca3(PO4)2 as the sole source of phosphorus and showed dissolved phosphorus content more than 200 ug mL-1.The two seasons seedling raising experiment showed that bio-nursery substrates added with strains NJAU-3,Y2,Y40,L-60,NJAU-5,69 and 84 exhibited obvious promoting effects on seedling growth.2.Microbial groups were constracted by the confrontation experiments between single strains screened in the present study and Bacillus amyloliquefaciens SQR9,a plant-growth promotion bacterial strain previously isolated in our lab and widely utilized in the field to improve crop production.The results showed that none antagonistic phonome was observed betweent strain SQR9 with the phosphate-solubilizing strains Y40,Y2,and NJAU-3 and the IAA-producing strains NJAU-5,L-60,69,and 84.After the chromogenic reaction of 7 screened strains on GEN III plate and the analysis of the carbon.reclosing relationship between strain SQR9 and each functional bacterium,the relatively maximum and minimal reclosing utilization of carbon source between strain SQR9 and each phosphate solubilizing bacterium are SQR9+Y40 and SQR9+Y2,respectively;the relatively maximum and minimal reclosing utilization of carbon source between strain SQR9 and each IAA-producing bacteria are SQR9+69 and SQR9+L60,respectively;the relatively maximum and minimal reclosing utilization of carbon source between strain SQR9 and two bacteria are SQR9+69+Y40 and SQR9+L60+Y2,respectively;the relatively maximum and minimal complementary utilization of carbon source between strain SQR9 and three bacteria are SQR9+Y40+69+94 and SQR9+Y2+L60+84,respectively.The results of two seasons seedling test experiments showed that there was a significant negative correlation between the coincidence number of carbon sources and plant growth promoting effect.Bio-nursery substrates added the six microbial groups(SQR9+Y2+L60+84,SQR9+Y2+L60,SQR9+Y2+L60,SQR9+Y2+84,SQR9+Y2 and SQR9+L60)with relatively less reclosing utilization of carbon source between strain SQR9 and function bacteria strains showed better plant growth promotion effect than bio-nursery substrates amended with single strain and CK(Ordinary nursery substrates amended without adding any strain).The plant growth promotion of bio-nursery substrates amended with group SQR9+Y2+L60 was significantly higher than that amended with single strain and CK.Bio-nursery substrates amended with groups of relatively more complementary utilization of carbon source between SQR9 and function bacteria showed better plant growth promotion effects than amended with single strain and CK,but there was no significant difference among them.Plus,compound liquid amino acids hydrolyzed by sulfuric acid solution from animal carcasses was added in the bio-nursery substrates produced by micaobial groups including SQR9+Y2+L60+84,SQR9+L60+84,SQR9+Y2+84,SQR9+L60,SQR9+69+84 and SQR9+Y40+84 to analysis the plant growth promotion effect of the combination of amino acids and functional microbes.Results showed that addition of amino acids showed better plant growth promotion effect that the bio-nursery substrates amended with water,but there was no significant difference.3.According to the seedling raising experiment,seedlings from the following nursery substrates were selected for pot experiments:bio-nursery substrates produced by SQR9+Y2+L60+84,SQR9+Y2+L60,SQR9+Y2+84,SQR9+Y2,SQR9+L60,SQR9,Y2,L60,84 and CK(ordinary nursery substrates).Treatments transplanted with seedlings from bio-nursery substrates produced by SQR9+Y2+L60 and SQR9+84+Y2 showed significant higher plant height,stem diameter and shoot fresh weight compared to treatments transplanted with seedlings from bio-nursery substrates produced by corresponding single bacterium,two bacteria(SQR9+Y2、SQR9+L60)and four bacteria(SQR9+Y2+L60+84)and CK.Treatments transplanted with seedlings from bio-nursery substrates produced by SQR9+Y2,SQR9+L60 or SQR9+Y2+L60+84 showed higher plant height,stem diameter,and shoot fresh and dry weight than compared to treatments transplanted with seedlings from bio-nursery substrates produced by corresponding single bacterium and CK,but there was no significant difference.The total number of culturable bacteria in bulk and rhizosphere soil samples of two treatments transplanted with seedlings from bio-nursery substrates produced by SQR9+Y2+ L60 and SQR9+Y2+84 were higher than those of other treatments.The results of pot experiment and seedling test experiment showed the best bio-nursery substrates were produced by microbial groups of SQR9+Y2+L60 and SQR9+Y2+84.In summary,the plant growth-promoting effect of multifunctional compoundmicrobial groups are constracted in this study.The results showed that there was a significant negative correlation between the coincidence number of microbial carbon source and plant growth promoting effect.This study can provide new ideas for the development of PGPR products. |
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