Prevalence and characterization of plant-parasitic nematodes in lowland and upland rice agro-ecosystems in Luzon, Philippines

The prevalence of plant-parasitic nematodes in lowland and upland rice ecosystems was compared based on soil and root samples from 30 rice fields in five provinces (Bataan, Batangas, Bulacan, Pampanga, and Pangasinan) of Luzon, Philippines. Five nematode genera (Meloidogyne, Hirschmanniella, Pratylenchus, Tylenchorhynchus, and Helicotylenchus) from lowland and nine genera (Rotylenchulus, Aphelenchoides, Criconematidae, Rotylenchus, and those found in lowland) from upland were identified. Meloidogyne graminicolawas the most prevalent and abundant plant-parasitic nematode in both ecosystems. Hirschmanniellawas the second most prevalent genus in lowland rice, but its density was low in upland rice. Pratylenchus was present in high densities, but was not widely distributed in either upland or lowland rice fields. The three most prevalent nematode species, M. graminicola, H. oryzae, and H. mucronata, were morphologically and molecularly characterized. Molecular analyses based on D2D3, ITS1-5.8-ITS2, and 18S rDNA regions generally showed an overall congruence, low intraspecific variation and agreement with classical morphological and morphometrical identifications. Se comparo la prevalencia de nematodos parasitos de plantas en ecosistemas de arrozales en tierras bajas y altas, basados en muestras de suelo y raices procedentes de 30 campos de arroz en cinco provincias (Bataan, Batangas, Bulacan, Pampanga, y Pangasinan) de Luzon, Filipinas. Se identificaron cinco generos de nematodos (Meloidogyne, Hirschmanniella, Pratylenchus, Tylenchorhynchus, y Helicotylenchus) procedentes de arrozales en tierras bajas y nueve generos procedentes de arrozales en tierras altas (Rotylenchulus, Aphelenchoides, Criconematidae, Rotylenchus, y aquellos encontrados en las tierras bajas). Meloidogyne graminicolafue el nematodo parasito de plantas mas prevalente y abundante en ambos ecosistemas. Hirschmanniellafue el segundo genero mas prevalente en arrozales de tierras bajas, aunque sus densidades fueron bajas en tierras altas. Se encontraron Pratylenchusen altas densidades, pero no estaban ampliamente distribuidos ni en arrozales de tierras bajas ni de altas. Se caracterizaron morfologica y molecularmente las tres especies mas prevalentes de nematodos parasitos de plantas, M. graminicola, H. oryzae, y H. mucronata. Analisis moleculares basados en las regiones D2D3, ITS1-5.8-ITS2, y 18S del rDNA mostraron congruencia, baja variacion intraespecifica y estuvieron en concordancia con las clasicas identificaciones morfologicas y morfometricas.