Population Dynamics and Virulence Patterns of Root-Knot Nematodes (Meloidogyne spp.) on Tomato in Poonch Highlands, Azad Jammu and Kashmir, Pakistan

Abstract

Root-knot nematodes (RKNs) are root parasites of tomatoes. The population dynamics of RKNs, including their incidence and prevalence, need to be explored in tomato crops from the Poonch Highlands of Azad Jammu and Kashmir. Overall, 50.6% of the surveyed tomato crop was found to be infested, with disease severity (galling index) ranging from 1 to 9. The highest RKN prevalence (77.8%) was recorded in Haveli, followed by Poonch (64.2%), Sudhnuti (47.6%) and the lowest in Bagh (41.6%). The highest disease severity (galling index 2–9) was observed in Poonch district, followed by Bagh district (1–9), while it was lowest in Haveli district (4–6), followed by Sudhnuti district (2–7). Morphological and molecular diagnostics confirmed the presence of tropical RKN species affecting tomato. Three major tropical RKN species were identified. Meloidogyne javanica was the most prevalent, occurring at 27.6% of the surveyed sites, followed by Meloidogyne incognita (23.5%) and Meloidogyne arenaria (18.8%). Mixed populations were found in fewer than 5% of sites for each combination. The highest prevalence of M. javanica (66.7%) was recorded in Haveli, while the lowest (9.5%) was in Sudhnuti. M. incognita and M. arenaria exhibited similar distribution patterns across all districts, ranging from 20.2% to 33.3% and 17.0% to 44.4%, respectively. Mixed-population infestations were relatively low in Bagh and Sudhnuti compared to Poonch and Haveli. Ecological diversity was found to influence species virulence and distribution patterns. This study highlights the virulence patterns of tropical RKN species, likely representing an indigenous fauna impacting tomato crops under field conditions in the temperate highlands.