Cyst nematodes, some of the most important plantparasitic nematodes globally, cause major damage to Chinese cabbage and soybean plants in Korea. Cysts are commonly used for cyst nematode bioassays because many eggs are included inside cyst. Traditionally, cysts are extracted from the soil using the paper strip method or the centrifugal flotation method (CFM) combined with sieving. The specific gravity of sugar solution (SGSS) is often used in the CFM; however, the efficiency of cyst extraction and egg hatching in the CFM has not been studied. In this study, we assessed the effects of SGSS in a specific gravity range of 1.15 to 1.30 in the CFM on the cyst extraction and egg hatching of clover cyst nematode (Heterodera trifolii) and sugar beet cyst nematode (H. schachtii). High SGSS in the CFM within the range of 1.15 to 1.30 was positively correlated with the extraction of more cysts. Egg-hatching rates were not different between SGSSs, indicating that SGSS did not directly affect egg-hatching rates. These results showed that the cysts of cyst nematodes can be efficiently extracted with high SGSS in the CFM.

The root-knot nematode, Meloidogyne incognita, poses a significant economic threat as an endoparasite for various vegetables, including cabbage. Utilizing botanicals is an essential aspect of green technology to combat root-knot nematode infection. This study investigates the efficacy of four botanicals (Oxalis corniculata, Ricinus communis, Lantana camara, and Pluchea lanceolata) as emerging phyto-nematicides against M. incognita using both in vitro experiments (J2 mortality after 24, 36 and 48 hours exposure to 3000, 2000, 1000, 500, and 0 mg/L of the four botanicals and then determination egg hatching of M. incognita after 3 and 5 days incubation with various concentrations of the selected botanicals) and pot experiments. In the in vitro study, different extracts from the leaves of botanicals were applied to the second juvenile stage (J2) of M. incognita. The highest mortality of J2 and reduction in egg hatching for O. corniculata extract (89.96 and 86.79%), while the lowest effects (9.01 and 11.50 %) were observed for P. lanceolata extract. The extract of O. corniculata caused complete damage to the morphology of J2 via rupturing the cuticle of posterior, middle, and interior portion. In the pot experiment, M. incognita adversely affected growth shoot length (51.37%), root length (55.10%), fresh head weight (63.14%), and dry head weight (61.79%) by down-regulation of biochemical and epidermal traits compared to un-inoculated plants. However, the soils amended with botanicals especially O. corniculata recorded highest retardation of M. incognita infestation in cabbage roots, hence improved the growth and yield compared to the infected plants. The most beneficial effect denoted by O. corniculata at 100 g/pot on the infected cabbage plants associated with improving carotenoids (83%), chorophyll (117%), and nitrate reductase activity (79%) compared to stressed plants only. Also, O. corniculata at 100 g/pot maximally increased the number of stomata (130%), lengths (87%), and width (141%) of stomatal pore infected cabbage plants compared to the infected plants. These findings recommended the importance of O. corniculata as an eco-friendly organic phyto-nematicide that effectively restrict the damaging impacts of M. incognita on cabbage and may be other crops.

Root-knot nematodes (RKNs) are a vital pest that causes significant yield losses and economic damage to potato plants. The use of chemical pesticides to control these nematodes has led to environmental concerns and the development of resistance in the nematode populations. Endophytic fungi offer an eco-friendly alternative to control these pests and produce secondary metabolites that have nematicidal activity against RKNs. The objective of this study is to assess the efficacy of Aspergillus flavus (ON146363), an entophyte fungus isolated from Trigonella foenum-graecum seeds, against Meloidogyne incognita in filtered culture broth using GC-MS analysis. Among them, various nematicidal secondary metabolites were produced: Gadoleic acid, Oleic acid di-ethanolamide, Oleic acid, and Palmitic acid. In addition, biochemical compounds such as Gallic acid, Catechin, Protocatechuic acid, Esculatin, Vanillic acid, Pyrocatechol, Coumarine, Cinnamic acid, 4, 3-indol butyl acetic acid and Naphthyl acetic acid by HPLC. The fungus was identified through morphological and molecular analysis, including ITS 1-4 regions of ribosomal DNA. In vitro experiments showed that culture filtrate of A. flavus had a variable effect on reducing the number of egg hatchings and larval mortality, with higher concentrations showing greater efficacy than Abamectin. The fungus inhibited the development and multiplication of M. incognita in potato plants, reducing the number of galls and eggs by 90% and 89%, respectively. A. flavus increased the activity of defense-related enzymes Chitinas, Catalyse, and Peroxidase after 15, 45, and 60 days. Leaching of the concentrated culture significantly reduced the second juveniles' stage to 97% /250 g soil and decreased the penetration of nematodes into the roots. A. flavus cultural filtrates via soil spraying improved seedling growth and reduced nematode propagation, resulting in systemic resistance to nematode infection. Therefore, A. flavus can be an effective biological control agent for root-knot nematodes in potato plants. This approach provides a sustainable solution for farmers and minimizes the environmental impact.