Université Clermont Auvergne, INRAE, PIAF, Clermont-Ferrand, France.
Université de Tunis El Manar, Campus Universitaire Farhat Hached, Tunis, Tunisia.
PLoS One. 2024 May 17;19(5):e0300791. doi: 10.1371/journal.pone.0300791. eCollection 2024.
Plant growth-promoting rhizobacteria (PGPR) applications have emerged as an ideal substitute for synthetic chemicals by their ability to improve plant nutrition and resistance against pathogens. In this study, we isolated fourteen root endophytes from healthy wheat roots cultivated in Tunisia. The isolates were identified based from their 16S rRNA gene sequences. They belonged to Bacillota and Pseudomonadota taxa. Fourteen strains were tested for their growth-promoting and defense-eliciting potentials on durum wheat under greenhouse conditions, and for their in vitro biocontrol power against Fusarium culmorum, an ascomycete responsible for seedling blight, foot and root rot, and head blight diseases of wheat. We found that all the strains improved shoot and/or root biomass accumulation, with Bacillus mojavensis, Paenibacillus peoriae and Variovorax paradoxus showing the strongest promoting effects. These physiological effects were correlated with the plant growth-promoting traits of the bacterial endophytes, which produced indole-related compounds, ammonia, and hydrogen cyanide (HCN), and solubilized phosphate and zinc. Likewise, plant defense accumulations were modulated lastingly and systematically in roots and leaves by all the strains. Testing in vitro antagonism against F. culmorum revealed an inhibition activity exceeding 40% for five strains: Bacillus cereus, Paenibacillus peoriae, Paenibacillus polymyxa, Pantoae agglomerans, and Pseudomonas aeruginosa. These strains exhibited significant inhibitory effects on F. culmorum mycelia growth, sporulation, and/or macroconidia germination. P. peoriae performed best, with total inhibition of sporulation and macroconidia germination. These finding highlight the effectiveness of root bacterial endophytes in promoting plant growth and resistance, and in controlling phytopathogens such as F. culmorum. This is the first report identifying 14 bacterial candidates as potential agents for the control of F. culmorum, of which Paenibacillus peoriae and/or its intracellular metabolites have potential for development as biopesticides.
植物促生根际细菌（PGPR）能够改善植物营养和提高对病原体的抗性，因此成为了替代合成化学品的理想选择。本研究从突尼斯种植的健康小麦根系中分离出 14 种根内生菌。根据 16S rRNA 基因序列对分离株进行鉴定，它们属于芽孢杆菌和假单胞菌门。在温室条件下，对 14 种菌株进行了促进冬小麦生长和诱导防御的潜力测试，并在体外对引起幼苗疫病、脚腐和根腐以及小麦赤霉病的镰孢菌进行了生物防治能力测试。我们发现所有菌株都能提高小麦地上部和/或根系生物量的积累，其中芽孢杆菌、佩氏假单胞菌和异形 VAR 菌的促进作用最强。这些生理效应与细菌内生菌的植物促生特性相关，内生菌能够产生吲哚类化合物、氨和氢氰酸（HCN），并溶解磷和锌。同样，所有菌株都能持久和系统地调节根部和叶片中的植物防御积累。体外对 F. culmorum 的拮抗作用测试表明，5 株菌对 F. culmorum 的抑制活性超过 40%：蜡样芽孢杆菌、佩氏假单胞菌、多粘类芽孢杆菌、成团泛菌和铜绿假单胞菌。这些菌株对 F. culmorum 菌丝生长、产孢和/或大分生孢子萌发有显著的抑制作用。佩氏假单胞菌表现最好，对产孢和大分生孢子萌发有完全抑制作用。这些结果突出了根内生细菌在促进植物生长和抗性以及控制 F. culmorum 等植物病原体方面的有效性。这是首次报道鉴定出 14 种细菌候选物作为控制 F. culmorum 的潜在药剂，其中佩氏假单胞菌及其细胞内代谢物可能具有作为生物农药的开发潜力。
