Kumar Kanchan, Kumar Deepak, Pal Gaurav, Verma Satish K
Department of Botany, Institute of Science, Banaras Hindu University, Varanasi, 221005, UP, India.
Department of Plant Breeding and Genetics, Dr. Rajendra Prasad Central Agricultural University, Pusa, Samastipur, Bihar, India.
World J Microbiol Biotechnol. 2025 Jul 3;41(7):246. doi: 10.1007/s11274-025-04455-y.
Seeds naturally harbour bacterial endophytes that act as primary symbionts of plants. This study aimed to isolate and characterise seed inhabiting bacterial endophytes of sorghum sudan grass and evaluate the most active endophyte, Bacillus amyloliquefaciens-SS7 for protecting seedlings against Rhizoctonia solani infection. Seven bacterial endophytes (SS1-SS7) were isolated from surface sterilized sorghum sudan grass seeds and identified via 16 S rRNA sequencing. All isolates were screened for plant growth promoting and antifungal activities. B. amyloliquefaciens-SS7 exhibited the highest siderophore production and strong antifungal activity. Gene screening confirmed the presence of antifungal lipopeptide genes (Iturin A and Bacillomycin D) in B. amyloliquefaciens. Extracted lipopeptides from B. amyloliquefaciens strongly inhibited R. solani in disc diffusion assays. Bright field and fluorescence microscopy revealed that lipopeptides caused structural deformations and cell death in R. solani. Microcosm assays demonstrated significant protection of seedlings inoculated with B. amyloliquefaciens from Rhizoctonia infection. Histological studies confirmed overproduction of superoxide ions and cell death in seedlings infected with R. solani. Biochemical analysis showed increased levels of phenylalanine ammonia-lyase (PAL), superoxide dismutase (SOD), and peroxidase (POX) in treated seedlings compared controls. Infections caused by R. solani targeted the collar region of seedlings, causing damping-off in those lacking the endophyte B. amyloliquefaciens. This study concludes that sorghum sudan grass seeds contain bacteria like B. amyloliquefaciens-SS7, which are crucial in protecting seedlings from R. solani. This research is the first to report on the role of seed endophytic bacteria (SEB) in the protecting sorghum sudan grass against R. solani.
种子天然携带着作为植物主要共生体的细菌内生菌。本研究旨在分离和鉴定苏丹草种子中的细菌内生菌，并评估最具活性的内生菌解淀粉芽孢杆菌 - SS7对幼苗抵御立枯丝核菌感染的保护作用。从表面消毒的苏丹草种子中分离出7种细菌内生菌（SS1 - SS7），并通过16S rRNA测序进行鉴定。对所有分离株进行了促进植物生长和抗真菌活性的筛选。解淀粉芽孢杆菌 - SS7表现出最高的铁载体产量和较强的抗真菌活性。基因筛选证实了解淀粉芽孢杆菌中存在抗真菌脂肽基因（伊枯草菌素A和芽孢霉素D）。在纸片扩散试验中，从解淀粉芽孢杆菌中提取的脂肽强烈抑制立枯丝核菌。明场和荧光显微镜观察表明，脂肽会导致立枯丝核菌的结构变形和细胞死亡。微观试验表明，接种了解淀粉芽孢杆菌的幼苗对立枯丝核菌感染具有显著的保护作用。组织学研究证实，感染立枯丝核菌的幼苗中超氧离子过量产生且细胞死亡。生化分析表明，与对照相比，处理过的幼苗中苯丙氨酸解氨酶（PAL）、超氧化物歧化酶（SOD）和过氧化物酶（POX）的水平有所增加。立枯丝核菌引起的感染靶向幼苗的颈部区域，导致缺乏内生菌解淀粉芽孢杆菌的幼苗猝倒。本研究得出结论，苏丹草种子含有像解淀粉芽孢杆菌 - SS7这样的细菌，它们对于保护幼苗免受立枯丝核菌侵害至关重要。本研究首次报道了种子内生细菌（SEB）在保护苏丹草免受立枯丝核菌侵害中的作用。
