Abundance and distribution of plant-parasitic nematodes in tomatoes grown in a semi-arid agro-ecological zone in Tanzania

Abstract

The abundance and distribution of plant-parasitic nematodes (PPN) on tomato plants grown in nine villages in the semi-arid zones of Singida and Dodoma in Tanzania were assessed in December 2020. Samples from soil and plant roots were evaluated for abundance, genera and distribution of PPN. Nematodes were extracted, counted and identified based on morphological descriptors. Ten genera of PPN were identified in both root and soil samples, with root-knot nematodes (RKN) being the most common PPN in all nine villages surveyed. The results showed that the abundance of RKN was significantly higher (p = 0.002) in soil than in tomato roots. Tutu and Chamkoroma villages had a significantly (p = 0.001) higher population density of RKN compared to other villages. In addition, RKN was associated with Penicillium and Aspergillus fungi, while the nematode genera Helicotylenchus, Aphelenchus, Scutellonema and Pratylenchus exhibited relationships with Alternaria and Fusarium fungi. The results also indicated that the abundance of RKN was significantly higher (p = 0.001) in sandy soil as compared to other types of soils. Inappropriate agronomical practices (e.g., no fallow, rotation of tomato plant with related crops) and poor phytosanitary measures were the major factors associated with high levels of abundance and distribution of RKN in soil.