Distribution and Associations of Plant-Parasitic Nematodes with Soil-Borne Fungi in Solanaceous Plantations of Al-Ahsa Oasis, Saudi Arabia

A comprehensive survey across three locations in Al-Ahsa Oasis (Saudi Arabia) was carried out to investigate the distribution, population density, and interactions of plant-parasitic nematodes and soil-borne fungi accompanying solanaceous crops (eggplant, pepper, potato, and tomato). A total of six nematode genera were identified, with Meloidogyne spp. accounting for the most prevalent (74% occurrence) and dominant in both loamy sand and sandy loam soils, with high densities especially in sandy loam soils. Other genera were represented by Rotylenchulus, Pratylenchus, Hoplolaimus, Tylenchorhynchus , and Helicotylenchus . The most common fungal pathogens were Fusarium solani and Fusarium oxysporum , and there was a significant positive correlation between the presence of F. solani , root rot severity, and nematode infestation levels. The texture of the soil emerged as a major factor affecting the composition of the nematode and fungal communities, where the co-occurrence of Meloidogyne and Fusarium was higher and root rot symptoms were more intense in soil with sandy loam texture in Al-Hofuf and Al-Omran than in loamy sand in Al-Bustan. Principal component analysis showed a high level of interaction between fungal and nematode populations that influences disease dynamics. These results underline the importance of nematode-fungus associations in intensifying root diseases and losses in crop yields of Solanaceous crops and present a necessity for integrated pest management options based on soil characteristics and local environmental factors to achieve sustainable crop production in arid areas.