药用野生稻拮抗稻瘟病内生细菌的筛选、鉴定及发酵条件优化

Screening, identification, and fermentation condition optimization of antagonistic endophytes from Oryza officinalis

摘要:

【背景】稻瘟病是水稻的三大重要病害之一，每年对水稻生产都会造成较大的损失，生物防治稻瘟病已成防治该病害的重要手段，而目前鲜少有报道从药用野生稻中分离内生菌用以防治稻瘟病。【目的】从药用野生稻内生菌中挖掘对稻瘟病具有拮抗作用的微生物资源。【方法】采用分离法从勐遮药用野生稻中先分离出内生菌，再通过平板对峙法筛选对稻瘟病菌具有拮抗作用的菌株，通过形态学和16s rRNA基因序列分析对菌株进行鉴定，同时筛选该菌株的最适培养基、pH、培养温度和摇床转速。【结果】筛选得到拮抗菌株Z5，在LB培养基上对稻瘟病菌菌丝生长的抑制率达到96.43%，经形态学和16S rRNA基因序列分析，初步鉴定为短小芽孢杆菌(Bacillus pumilus)。在NYBD、CM、LB、NA和YSP这5种培养基中，菌株Z5的最适培养基为NYBD培养基、最适pH值为8.0−9.0、最适培养温度为35 ℃、最适摇床转速为250 r/min。【结论】短小芽孢杆菌Z5对稻瘟病菌的生长具有较好的抑制作用，且该菌株耐高温、较耐酸碱，作为稻瘟病生防制剂研发具有一定的价值。

Abstract:

[Background] Rice blast, one of three major diseases of rice, causes great losses to rice production every year. Biocontrol has become a key means for the prevention and control of this disease. However, there are few endophytes isolated from Oryza officinalis Wall. for the control of this disease at present. [Objective] To excavate the microbial resources against rice blast from the endophytes of O. officinalis. [Methods] The endophytes were isolated from O. officinalis, screened by the plate confrontation method, and identified based on morphological characteristics and 16S rRNA gene sequences. Furthermore, we optimized the medium, pH, temperature, and shaking speed for the fermentation of the strain screened out. [Results] The antagonistic strain Z5 was screened out and identified as Bacillus pumilus, with the inhibition rate of 96.43% on the mycelial growth of Magnaporthe grisea in the LB medium. Strain Z5 showed the best growth in the NYBD medium among the five medium tested (NYBD, CM, LB, NA, and YSP) and at pH 8.0–9.0, 35 ℃, and 250 r/min. [Conclusion] B. pumilus Z5 exerted a good inhibitory effect on the growth of M. grisea and can tolerate high temperature, acid, and alkali, demonstrating the potential of serving as a biocontrol agent for rice blast.