Chinese leek (Allium tuberosum Rottler ex Sprengel) reduced disease symptom caused by root-knot nematode

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.