Root-knot nematodes (RKNs) cause severe losses in kiwifruit-growing regions. The endophytic bacteria could be biological agents for nematodes management. The aim of this study was the isolation and identification of endophytic bacteria from kiwifruit orchards and the evaluation of their antagonistic ability against RKN in greenhouse conditions. In this study, the population of nematode and the bacterial strains were isolated from kiwifruit roots and leaves in the Mazandaran and Guilan provinces of Iran. Molecular experiments were conducted to identify and confirm the bacterial isolates and RKN species. Also, the effects of bacterial isolates on nematode reproduction factors (number of galls, egg masses, and second-stage juveniles, J2) and growth parameters of kiwifruit plants were determined. The RKN was confirmed as Meloidogyne incognita by molecular identification. Also, the endophytic bacteria were identified based on supplementary experiments and molecular analyses. A total of 31 bacterial endophytes were identified to be including 12 genera of Bacillus, Pseudomonas, Staphylococcus, Exiguobacterium, Sphingomonas, Agrobacterium, Variovorax, Pantoea, Microbacterium, Streptomyces, Chryseobacterium, and Chitinophaga. Generally, Bacillus and Pseudomonas were the dominant genera that included 29.03 and 22.58% of total isolated bacteria, respectively. In vitro screening assays, P. ananatis 121.en and P. chlororaphis 54.en displayed considerable antagonistic ability on J2 mortality of M. incognita and were selected for greenhouse surveys. The isolates displayed a significant reduction in the number of galls and egg masses on roots and juvenile’s population in pot soil. Moreover, 121.en and 54.en strains significantly increased growth parameters including root fresh weight and shoot fresh weight than the control kiwifruit seedlings. The bacterial endophytes are safe and have a low risk of managing the RKNs and can be effective microbial bio-fertilizers for improving kiwifruit plant growth under RKNs infections.

中文翻译：

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猕猴桃相关内生菌的分离鉴定及其对南方根结线虫的生防潜力

根结线虫 (RKNs) 在猕猴桃种植区造成严重损失。内生细菌可能是线虫管理的生物制剂。本研究的目的是从猕猴桃园中分离和鉴定内生细菌，并评估它们在温室条件下对 RKN 的拮抗能力。在这项研究中，线虫种群和细菌菌株是从伊朗马赞达兰省和桂兰省的猕猴桃根和叶中分离出来的。进行分子实验以鉴定和确认细菌分离物和 RKN 物种。此外，还确定了细菌分离物对线虫繁殖因子（虫瘿数、卵块数和第二阶段幼虫数，J2）和猕猴桃植物生长参数的影响。通过分子鉴定，RKN被确认为南方根结线虫。此外，根据补充实验和分子分析鉴定了内生细菌。共鉴定出 31 种细菌内生菌，包括芽孢杆菌属、假单胞菌属、葡萄球菌属、微小杆菌属、鞘氨醇单胞菌属、农杆菌属、杂食菌属、泛菌属、微杆菌属、链霉菌属、金黄杆菌属和几丁质菌属 12 属。一般来说，芽孢杆菌属和假单胞菌属占优势菌属，分别占总分离菌量的29.03%和22.58%。在体外筛选试验中，P. ananatis 121.en 和 P. chlororaphis 54.en 对 M. incognita 的 J2 死亡率表现出相当大的拮抗能力，并被选择用于温室调查。分离株在盆土中根部和幼虫种群中的虫瘿和卵块数量显着减少。此外，与对照猕猴桃幼苗相比，121.en和54.en菌株显着增加了包括根鲜重和地上部鲜重在内的生长参数。细菌内生菌是安全的，管理RKNs的风险低，可以成为有效的微生物肥料，用于改善RKNs感染下猕猴桃植物的生长。