Chinese leek (Allium tuberosum Rottler ex Sprengel) is a common vegetable in China.  In our previous study, Chinese leek in rotation was found to have significant antifungal and nematicidal activity.  This study’s aim was to investigate the potential antifungal and nematicidal activity associated with rhizosphere or endophytic microbes of Chinese leek.  Thus, a total of 79 261 high-quality sequences were obtained from Chinese leek rhizosphere soil, leaf and root samples.  In the rhizosphere soil, the bacterial community comprised five dominant phyla: Proteobacteria (37.85%), Acidobacteria (10.99%), Bacteroidetes (8.24%), Cyanobacteria (7.79%) and Planctomycetes (7.1%).  The leaf and root bacterial communities comprised two dominant phyla: Cyanobacteria (83.42% in leaf and 75.44% in root) and Proteobacteria (14.75% in leaf and 21.04% in root).  Microbial diversity, richness and evenness in the rhizosphere soil bacterial community were higher than that in the endophytic bacterial communities.  The rhizosphere bacterial community was significantly different from the endophytic bacterial communities.  The endophytic bacterial communities from the leaf and the root were slightly, but not significantly different from each other.  This study’s findings would contribute to the isolation and identification of nematicidal and antifungal bacterial communities in Chinese leek.

Root-knot nematodes (RKNs, Meloidogyne spp.) are obligate biotrophic parasites that settle close to the vascular tissues in plant roots. The diseases resulting from RKN infections cause serious damage to agricultural production worldwide. In the present paper, the resistance of Chinese leek (Allium tuberosum Rottler ex Sprengel) against RKNs, its suppressive effect on nematode disease, its nematicidal activity and its component profile were studied to identify an efficient disease control method. In soil heavily infected by nematodes, Chinese leek showed strong resistance to RKNs. Additionally, the gall indexes of cucumber plants rotated with Chinese leek and of tomato plants intercropped with Chinese leek were reduced by 70.2 and 41.1%, respectively. In a pot experiment, the gall indexes of Chinese leek extract-treated tomato and cucumber plants were reduced by 88.9 and 75.9%, respectively. In an in vitro experiment, the mortality rate of a RKN (Meloidogyne incognita J2) treated with Chinese leek extract was significantly higher than that of the control. The gas chromatography- mass spectrometry (GC-MS) analysis revealed that glycosides, carboxylic acids, ketones and organic sulfides are the main components in the Chinese leek extract. This study revealed that Chinese leek possesses a high resistance to RKNs, has strong nematicidal activity against M. incognita and can significantly reduce the incidence of disease caused by nematodes.