西瓜根际促生菌筛选及生物育苗基质研制

通过从西瓜根际分离筛选具根际定殖能力的植物根际促生菌,将其保活添加至普通育苗基质研制生物育苗基质,以确保功能菌株能够在苗期定殖根际,进而在移栽后发挥促生功能。结果表明,分离获得一株同时具有产吲哚乙酸(IAA)和NH_3,且对尖孢镰刀菌和茄科劳尔氏菌均有拮抗作用的植物根际促生菌(PGPR)菌株N23;在三季育苗试验中,与普通基质处理(CK)相比,添加菌株N23的生物育苗基质所育种苗,在多项苗期生长指标上均表现出稳定的促生作用;盆栽试验表明,除叶绿素相对含量测量值(SPAD)外,生物基质所育西瓜种苗的其他检测指标均显著高于对照(普通育苗基质所育种苗,下同);田间试验表明,生物基质所育种苗西瓜、黄瓜、辣椒和番茄种苗移苗后,在苗期植株株高和茎粗均显著优于对照,在产量上均增产10%以上。结合形态、生理生化特征和16S rDNA基因序列分析,初步鉴定菌株N23为芽孢杆菌属细菌(Bacillus sp.)。综上,利用芽孢杆菌N23研制的生物育苗基质能够有效促进所育不同作物种苗质量,增强移栽后作物的生长和田间产量。因此,本研究能够为根际有益微生物的应用提供新的思路,为生物育苗基质的研制提供理论支撑。

Screening of Plant Growth-Promoting Rhizobacteria from Watermelon and Development of Bio-nursery Substrates

Objective]In order to improve the technical level of industrialized seedling culture and find new methods to make use of plant growth-promoting rhizobacteria(PGPR),a new strain of functional bacteria that would promote growth of watermelon was isolated,cultured and inoculated into ordinary nursery substrate,thus forming a kind of bio-nursery substrate. Method] A number of strains of bacteria were isolated randomly from the rhizosphere soil of watermelon plants and screened by plant growth-promoting properties. One strain which was found to possess complex functions and efficient rhizospheric colonization ability was further cultured and then inoculated into in ordinary nursery substrate in developing bio-nursery substrates. Repeated seedling nursing tests and pot experiments were performed in greenhouse and subsequently in the field to further validate effect of the novel bio-nursery substrate prepared by inoculating this bacterial strain into ordinary nursery substrate. In the end this strain was proved to be the right one for preparation of bio-nursery substance. Result] Through screening,a strain of bacteria,N23,capable of both producing indole acetic acid and NH3 simultaneously and acting in antagonism against Fusarium oxysporum f. sp. niveum and Ralstonia solanacearum,was isolated from the rhizospheric soil of watermelon plants. Seedling raising experiments show that in the substrate inoculated with Strain N23,watermelon seedlings grew much better than those in the ordinary nursery substrate,in plant height,stem diameter and leaf area. Such an effect was further demonstrated in another three seedlings raising experiments,showing that the strain steadily promotes seedling growth in a number of growth indices. The pot experiments show that the plants growing in the bio-nursery substrate were significantly higher than those in the ordinary nursery substrate,in all measured parameters except SPAD(Soil and Plant Analyzer Development),which differed very slightly. In the field experiments,watermelon,cucumber,tomato,and pepper seedlings cultured in the bio-nursery substrate grew better than those cultured in ordinary nursery substrate,in plant height and stem diameter,which coincided with the results in the pot and seedling experiments. And in the two seasons of field experiments,the watermelon in the former was 12.5% and 25.4% higher than that in the latter,respectively. In the field experiments cucumber,tomato,and pepper in the former was 18%,60% and 25%,than their respective one in the latter. Morphological and biochemical analysis and 16S rDNA gene sequencing of Stain N23 shows that the strain is one of Bacillus sp. Conclusion] All the findings in this study demonstrate that the bio-nursery substrate prepared by inoculating Bacillus sp. N23 into ordinary nursery substances promotes seedlings and plant growth as well as yield of the crop. Consequently,this study has provided some novel ideas for making use of rhizobacteria and some theoretical and technical support to the development of PGPR agents for preparation of bio-nursery substances.