The plant rhizosphere is a major habitat for diverse microorganisms because of its heterogeneous microenvironment. It is well known that an imbalance in rhizosphere microorganisms has direct and indirect effects on soil fertility and plant health. In this study, we investigated the impact of Lysobacter antibioticus 13–6 seed coat treatment on the soil physicochemical properties, plant growth, and bacterial community composition of maize plants in both in vivo and in vitro experiments, using high-throughput amplicon sequencing of 16S rRNA. Under in vitro conditions, we determined that L. antibioticus 13–6 has the ability to solubilize P, hydrolyze cellulose, and synthesize indole acetic acid. Furthermore, under in vivo conditions, L. antibioticus 13–6 significantly improved the soil physicochemical properties and enhanced the root length, stalk height, dry weight of root and stalk, grain yield, and chlorophyll contents by successful colonization in the rhizosphere of maize plants. The results of high-throughput amplicon sequencing of 16S rRNA demonstrated that L. antibioticus 13–6 significantly changed the diversity and composition of the rhizosphere bacterial communities. The relative abundance of Gammaproteobacteria, Gemmatimonadetes, and Bacteroidetes at the phylum level and Streptomyces, Lysobacter, and Nitrospira at the genus level significantly increased in the rhizosphere of L. antibioticus 13–6 seed coat-treated plants. Co-occurrence networks analysis revealed that the rhizosphere of L. antibioticus 13–6 seed coat-treated plants had fewer negative correlations and less competition for resources among bacterial communities. Genome analysis of L. antibioticus 13–6 revealed that the genome of L. antibioticus 13–6 encodes genes related to indole acetic acid synthesis, chitinase decomposition, and P solubilization, making it one of the most potent plant growth-promoting bacteria. Overall, this study demonstrated the potential of L. antibioticus 13–6 as a promising seed coat bioagent for sustainable agriculture and to minimize the utilization of agrochemicals.

玉米茎腐病是一种在世界玉米产区普遍发生的土传病害,根据病原菌的不同,玉米茎腐病分为细菌性茎腐病和真菌性茎腐病.玉米细菌性茎腐病病原主要有短小芽孢杆菌(Bacillus pumilus Meyer and Gottheil)[1]、玉米狄克氏菌(Dickeya ze-ae Samson et al.)[2]、铜绿假单胞杆菌(Pseudo-monas aeruginosa)[3]、成团泛菌(Pantoea agglom-erans)[4]等.玉米细菌性茎腐病导致玉米茎部腐烂并散发腥臭味,折断后导致玉米不能抽穗和结实,严重影响玉米产量[5].

玉米小斑病是玉米生产中的重要病害之一,本研究利用传统植物病理学和荧光定量PCR方法,研究抗生素溶杆菌对玉米小斑病菌(Bipolaris maydis)的生防效果和作用机制,为玉米小斑病的生物防控提供理论依据.结果显示,抗生素溶杆菌13-6对玉米小斑病菌丝生长和孢子萌发具有显著抑制作用,造成菌丝顶端生长受阻、表面粗糙,部分菌丝破裂,代谢粗提物抑制孢子萌发率高达92.19％,PI荧光染色显示病原菌孢子破裂并死亡.温室叶面喷施13-6发酵液、发酵液粗提物后显著降低玉米小斑病病情指数,相对防效分别达到42.43％和68.06％.诱导抗性实验表明:13-6对玉米小斑病的诱导防效达49.57％.玉米植株体内相关抗性基因表达结果显示,在灌根处理3 d后,抗病相关基因PR1和PR5、脂氧合酶LOX、乙烯受体ETR1均被激活表达,9 d达到最大值.研究证实抗生素溶杆菌13-6对玉米小斑病具有较好的生防效果,直接喷施可减缓玉米小斑病的发生,灌根施用使植株产生诱导抗性.

[目的]研究云南玉米大豆间作模式对玉米根际微生物群落特征、玉米产量及病害的影响,为玉米大豆间作模式的田间应用提供科学依据.[方法]采用单因素随机区组试验,通过设置玉米大豆间作和玉米单作处理,利用Illumina Miseq高通量测序技术分析间作玉米根际土壤微生物群落结构及其多样性,并进行玉米产量、病害发生与根际微生物变化之间的相关性分析.[结果]间作玉米产量显著高于单作玉米产量(P＜0.05);与单作相比,间作后玉米锈病、玉米灰斑病、玉米小斑病和玉米大斑病的病情指数显著降低;间作可提高玉米根际土壤微生物多样性指数(真菌和细菌Observed_species指数、Chaol指数和Shannon指数).差异OTUs分析结果显示:细菌中276个OTUs在玉米大豆间作中显著富集,251个OTUs在玉米单作中显著富集,芽单孢菌属(Gemmatimonas)和溶杆菌属(Lysobacter)等菌属的数量在玉米大豆间作中显著升高,伯克氏菌属(Burkholderia)和鞘脂菌属(Sphingobium)等菌属的数量显著降低;真菌中146个OTUs在玉米大豆间作中显著富集,141个OTUs在玉米单作中显著富集,被孢霉属(Mortierella)和壶菌属(Spizellomyces)等菌属丰度在玉米大豆间作中显著升高,而镰刀菌属(Fusarium)和梭杆菌属(Monographella)等菌属丰度显著降低.功能注释结果显示:玉米大豆间作能使玉米根际土壤中具有促进氮元素转化、有机物分解和改善土壤结构功能的有益微生物的丰度增加,而注释到潜在致病菌有害微生物丰度降低.[结论]玉米大豆间作改变了玉米根际微生物的群落结构,提高了细菌和真菌的多样性,使根际土中有益微生物数量增加,同时潜在致病菌等有害微生物数量降低,提高了玉米的抗病能力,增加了产量.