Linking soil nematode community structure with pomegranate root phytochemicals in Limpopo Province, South Africa

Abstract

Abstract This study examined the diversity, functional structure, and ecological relationships of nematode communities associated with the rhizosphere of pomegranate ( Punica granatum L.) in Limpopo Province, South Africa, with particular focus on their interaction with soil physicochemical properties and root phytochemicals. A total of 20 nematode genera were identified, representing five feeding guilds: herbivorous, bacterivorous, fungivorous, predators, and omnivorous. The nematode assemblage showed that herbivorous taxa (P-p class 3) were represented by Rotylenchulus , Helicotylenchus , Pratylenchus , Tylenchorhynchus , and Rotylenchus , while bacterivorous nematodes ( Acrobeloides , Pseudacrobeles, Prismatolaimus, Geomonhystera ) accounted for the largest proportion of free-living nematodes. Food web analysis showed a gradient from disturbed, nitrogen-enriched systems (high enrichment index, low structure index) to mature, structured webs, indicating variation in soil fertility and biological regulation across the orchard. Principal component analysis (PCA) explained 100% of total variation (PC1 = 55.08%, PC2 = 44.92%), revealing that nematode distribution was primarily driven by soil pH, electrical conductivity (EC), and nitrogen content. Pratylenchus and Rotylenchulus were negatively correlated with EC ( r = -0.99). In addition, Pratylenchus and Rotylenchulus showed strong positive correlations with ammonia ( r = 0.99) and nitrate ( r = 0.98). Phytochemical analysis revealed that total phenolic, flavonoid, flavonol, and tannin contents were negatively correlated with Tylenchorhynchus ( r = -0.866) and Xiphinema ( r = -0.866), suggesting suppression of these nematodes by polyphenolic compounds and Trichodorus ( r = 0.866), suggesting an increase in this nematode by polyphenolic compounds. In conclusion, the findings highlight the regulatory role of root phytochemicals and soil properties in shaping nematode community composition, indicating that phenolic-rich pomegranate roots may contribute to natural suppression of herbivorous nematodes and enhance soil ecological stability.