荔枝霜疫霉拮抗菌资源筛选与功能评价

Screening and functional evaluation of antagonistic bacterial resources against litchi downy blight

摘要:

荔枝(Litchi chinensis Sonn.)是我国重要的热带、亚热带水果。由荔枝霜疫霉(Peronophythora litchii Chen ex Ko et al.)侵染引起的荔枝霜疫病严重危害荔枝的生产和采后贮藏过程，是我国荔枝产业健康发展的重大威胁。目的 筛选高效拮抗荔枝霜疫霉的细菌菌株并评价其植物促生潜力，以丰富荔枝霜疫霉拮抗菌资源库。方法 采集荔枝根围土壤样品，采用高通量培养法分离细菌，基于16S rRNA基因序列进行菌株鉴定。采用平板对峙法筛选拮抗荔枝霜疫霉的活性菌株，并通过功能平板测定评价拮抗菌株的促生功能(溶磷、解钾、固氮、产铁载体、产吲哚乙酸)。结果 共分离获得细菌327株，其中92株对荔枝霜疫霉表现出拮抗活性(菌丝生长抑制率大于40%，分离到拮抗菌的阳性率达28.13%)。这些拮抗菌株系统发育多样，涵盖4门[主要为芽孢杆菌门(Bacillota)和假单胞菌门(Pseudomonadota)] 6纲12目20科42属，其中芽孢杆菌属(Bacillus)和类芽孢杆菌属(Paenibacillus)为优势属。对92株拮抗菌的促生功能评价显示：55株菌(占59.8%)具备至少一种促生能力；30株菌(占32.6%)同时具备3种以上促生能力。综合拮抗活性和促生功能，发现兼具抗病和促生功能的短芽孢杆菌属(Brevibacillus)的菌株T101、4株类芽孢杆菌属(Paenibacillus)的菌株(T431、T270、T327和T234a)，及副伯克霍尔德氏菌属(Paraburkholderia)的菌株R116b是最具生防应用潜力的菌株。结论 本研究成功筛选出多株兼具拮抗荔枝霜疫霉活性与多种促生功能(溶磷、解钾、固氮、产铁载体、产吲哚乙酸)的细菌菌株，为荔枝霜疫病的绿色防控及荔枝生态友好型种植体系的构建提供了宝贵的微生物资源。

Abstract:

Litchi (Litchi chinensis Sonn.) is one of the important tropical and subtropical fruits in China. However, litchi downy blight caused by the infection of Peronophythora litchii (Peronophythora litchii Chen ex Ko et al.) a severe disease damaging litchi during production, storage, and transportation, seriously threatening the healthy development of China’s litchi industry.Objective We screened effective antagonistic bacteria against P. litchii and evaluated their plant growth-promoting potential, aiming to enrich the resources of antagonistic bacteria against P. litchii.Methods Soil samples from the litchi rhizosphere were collected, and the bacteria in the samples were isolated through a high-throughput isolation and culture method. The strains were identified by means of 16S rRNA gene sequence analysis. The antagonistic strains against P. litchii were screened via the plate confrontation method, and the plant growth-promoting functions [phosphorus solubilization, potassium solubilization, nitrogen fixation, siderophore secretion, and indole-3-acetic acid (IAA) production] of the antagonistic strains were further evaluated through functional plates.Results A total of 327 bacterial strains were isolated in this study, among which 92 (28.13%) strains were identified as antagonists (with mycelial growth inhibition rates>40%) against P. litchii. These antagonistic strains belonged to 4 phyla, 6 classes, 12 orders, 20 families, and 42 genera, with Bacillota and Pseudomonadota being the dominant phyla, and Bacillus and Paenibacillus as the dominant genera. Functional evaluation of the 92 antagonistic strains revealed that 55 (59.8%) strains exhibited more than one plant growth-promoting function, while 30 (32.6%) strains possessed three or more such functions. Through comprehensive evaluation of antagonistic activity and plant growth-promoting functions, one Brevibacillus strain T101, four Paenibacillus strains (T431, T270, T327, and T234a), and one Paraburkholderia strain R116b were identified as the most promising strains for biocontrol applications.Conclusion Multiple antagonistic strains against P. litchi, with functions of phosphorus solubilization, potassium solubilization, nitrogen fixation, siderophore secretion, and IAA production, are screened out, which provides efficient strain resources for the green control of litchi downy blight.