Abstract
Until recently, the stem gall nematode Pterotylenchus cecidogenus was only registered in eastern Colombia. However, the disease has recently been observed in central Colombian oil palm plantations that use Desmodium ovalifolium as a cover crop. Soil, root, stem, and leaf samples were collected from D. ovalifolium. Plants showed foliar yellowing, leaf drying, and galls within stem nodes. Nematodes were identified, and the distribution, population density, and relative importance of different genera were determined. We performed morphometric and molecular identification of nematodes associated with gall symptoms. The D2-D3 segment of the large subunit-28S of ribosomal ribonucleic acid (RNA) and internal transcribed spacer (ITS) was sequenced, and phylogenetic analysis was performed. P. cecidogenus mainly occurred in the galls and to a lesser extent in the roots and soil. Nematodes were not found in leaf or inflorescence tissue. Morphological and morphometric data confirm the presence of P. cecidogenus in the stems of D. ovalifolium with gall symptoms. This study is the first to report deoxyribonucleic acid (DNA) sequences of P. cecidogenus. Based on D2-D3 and ITS partial sequences, P. cecidogenus is a sister species of the leaf-galling nematode Ditylenchus phyllobius (Sinm. Orrina phyllobia).
Highlights
Colombia is the fourth largest palm oil producer in the world and the first in Latin America
We collected 30 samples from 30 plots located on 28 palm oil plantations in the departments of Cesar (26), Santander (3), and Norte de Santander (1), all of which utilized Desmodium ovalifolium as the cover crop (Table 1)
The symptoms observed in diseased plants of D. ovalifolium used as a cover crop in oil palm in central
Summary
Colombian oil palm production is affected by two lethal diseases (sudden wilt and lethal wilt) In both cases, the primary management strategy is to eliminate grasses and establish legume cover crops (Arango et al, 2011; Sierra et al, 2014). The nematode does not need wounds to penetrate the stem, injuries caused by mechanical damage are quickly colonized by the parasite (Lehman, 1991). This nematode’s life cycle takes approximately 2 weeks and presents four juvenile stages (the first occurring inside the egg) for female members; far, male members have not been identified (Stanton, 1990). Nematodes move very little in the soil, and so it is difficult to find them in soil samples
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