Yunnan Agricultural University
枯草芽孢杆菌L1-21菌株是一株能高效抑制柑橘黄龙病菌和溃疡病菌的柑橘内生细菌。为在实际应用时提供理论依据,本研究通过向柑橘叶片喷施106cfu/mL 的L1-21菌株的绿色荧光标记菌(L1-21-GFP)发酵液,探究其在叶片内的定殖动态及传导能力；采用108cfu/mL的菌液喷施和浸泡处理柑橘果实,研究其在果实内的定殖能力,用注射接种Penicillium digitatum孢子和计算发病率,测定其对绿霉病的防控效果。结果表明,处理后10min,L1-21-GFP在叶表及叶肉中的定殖量分别达到1.36×103cfu/cm2和8.08×102cfu/cm2,并呈现持续增长的趋势。处理后1h,L1-21-GFP向下传导到叶表的菌含量为1.51×102cfu/cm2,并稳定存在于叶表中；处理后2h,传导到叶肉的菌含量为5.67cfu/cm2,逐渐增加到30h的1.15×103cfu/cm2。L1-21-GFP能在果实内定殖,浸泡1h果肉和果皮中的定殖量分别为9.51×103cfu/g和3.51×104cfu/g,但在不同柑橘品种果实间定殖能力有显著性差异,椪柑中定殖量最高。浸泡30min后,L1-21对果实绿霉病防效第3天为100%,第5天为80.36%；本研究结果对L1-21田间应用有重要指导意义。
Bacillus subtilis L1-21 is an endophytic bacterium to effectively inhibit citrus huanglongbing and canker disease pathogens. In order to provide theoretical basis for practical application, this study investigated the colonization dynamics and downward-conduction of B. subtilis green fluorescent labelled strain (L1-21-GFP) in citrus leaves by foliar spraying suspension with 106cfu/mL. Colonization in citrus fruits was checked through spraying and soaking with 108cfu/mL and control effect was evaluated on green mold by spore injection with Penicillium digitatum and incidence investigation. After 10min treatment, the colonization of B. subtilis L1-21-GFP in leaf surface and mesophyll reached 1.36×103cfu/cm2 and 8.08×102cfu/cm2, respectively, and displayed a continuous increasing trend. One hour after treatment, the GFP-tagged endophyte was stable in leaf surface with 1.51×102 cfu/cm2. The bacterial concentration reached to 5.67 cfu/cm2 in mesophyll after 2 h, which gradually increased to 1.15×103cfu/cm2 after 30h. Endophyte L1-21-GFP could easily colonize in fruits, and bacterial concentration in pulp and peel after 1h was 9.51×103cfu/g and 3.51×104cfu/g, respectively. However, there was significant difference in the colonization ability among fruits of different citrus varieties, and Citrus Reticulata cv Ponkan had the highest colonization. In addition, citrus green mold was successfully control on third and fifth day with 100% and 80.36% control effect, respectively, when soaked once with the bioagent for 30 min. Taken together, overall results of this study could guide us to apply B. subtilis L1-21 for field application of potential citrus diseases.