RESUMO
The objective of this research was to determine the potential use of eco-friendly technologies to reduce the clubroot disease caused by Plasmodiophora brassicae, the main constraint of cruciferous crops worldwide. Two commercial bioproducts were evaluated in susceptible broccoli, one based on the PGPR consortium (Bacillus amyloliquefaciens, Bacillus pumilus, and Agrobacterium radiobacter K84) and the other one based on Trichoderma koningiopsis Th003 (Tricotec® WG). Additionally, the resistant broccoli cv. Monclano® was tested under two concentrations of resting spores (RS) of P. brassicae, 1 × 103 and 1 × 105 RS g-1 of soil. The first phase of evaluations with broccoli was carried out under a greenhouse, while susceptible broccoli, cauliflower, and red cabbage were included in a subsequent field phase. Tebuconazole + Trifloxystrobin mixture and Fluazinam were included as positive controls. The effectiveness of the bioproducts depended on the nature of the biocontrol agent, the concentration of P. brassicae, and the dose of treatment. Tricotec® showed consistent plant growth promotion but no biocontrol effect against clubroot, and the rhizobacteria-based bioproduct significantly reduced the disease in both greenhouse and field experiments. Higher disease severity was observed with the higher dose of Tricotec®. Under field conditions, the rhizobacteria reduced the incidence progress by 26%, 39%, and 57% under high, medium, and low pressure of the pathogen, respectively. However, no reduction of clubroot severity under high pressure of the pathogen was observed. Complete inhibition of club formation in roots was achieved via the fungicide, but a phytotoxic effect was observed under greenhouse conditions. Fungicides reduced the incidence progress of clubroot, but not the severity under high inoculum pressure in the field. The fungicides, the bacterial treatment, and the combination of bioproducts tended to delay the progress of the disease compared with the negative control and Tricotec alone. The resistant broccoli showed a low level of disease under high concentrations of P. brassicae (less than 10% incidence and up to 2% severity). These results suggested the overall potential of commercial tools based on the PGPR consortium and plant resistance to control P. brassicae. The integration of control measures, the role of Trichoderma spp. in P. brassicae-cruciferous pathosystems, and the need to recover highly infested soils will be discussed.
RESUMO
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).
RESUMO
In total, 10 populations of Helicotylenchus associated with Musa spp., six from Colombia, and four from Brazil were identified to the species level. Morphological and morphometric data were recorded for each population, performed a principal components analysis (PCA), a conglomerate, along with consensus sequences of D2 to D3 expansion segment of the large subunit of ribosomal DNA (28S) for different populations. Identify of species were performed using the basic local alignment search tool (BLAST), and the evolutionary relationships of species were explored using a phylogeny study. Four species of Helicotylenchus were identified based on morphological and morphometric data: H. multicinctus, H. dihystera, H. erythrinae, and H. californicus. PCA and conglomerate analysis clearly separated these species. BLAST and phylogenetic analysis confirmed the presence of these species associated with Musa spp. crops. This is the first report of these species in Colombia through integrative taxonomy.In total, 10 populations of Helicotylenchus associated with Musa spp., six from Colombia, and four from Brazil were identified to the species level. Morphological and morphometric data were recorded for each population, performed a principal components analysis (PCA), a conglomerate, along with consensus sequences of D2 to D3 expansion segment of the large subunit of ribosomal DNA (28S) for different populations. Identify of species were performed using the basic local alignment search tool (BLAST), and the evolutionary relationships of species were explored using a phylogeny study. Four species of Helicotylenchus were identified based on morphological and morphometric data: H. multicinctus, H. dihystera, H. erythrinae, and H. californicus. PCA and conglomerate analysis clearly separated these species. BLAST and phylogenetic analysis confirmed the presence of these species associated with Musa spp. crops. This is the first report of these species in Colombia through integrative taxonomy.
RESUMO
The red ring nematode (Bursaphelenchus cocophilus (Cobb) Baujard 1989) has been registered in oil palm crops in the North, Central and Eastern zones of Colombia. In Tibu (North Santander), there are doubts regarding the diagnostic and identity of the disease. Oil palm crops in Tibu with the external and internal symptoms were inspected, and tissue samples were taken from different parts of the palm. The refrigerated samples were carried to the laboratory of Oleoflores in Tibu for processing. The light microscopy was used for the quantification and morphometric identification of the nematodes. Specimens of the nematode were used for DNA extraction, to amplify the segment D2-D3 of the large subunit of ribosomal RNA (28S) and perform BLAST and a phylogeny study. The most frequently symptoms were chlorosis of the young leaves, thin leaflets, collapsed, and dry lower leaves, beginning of roughening, accumulation of arrows and short leaves. Bursaphelenchus, was recovered in most of the tissues from the samples analyzed: stem, petiole bases, inflorescences, peduncle of bunches, and base of arrows in variable populations. The morphometric data and sequences obtained for the segment D2-D3 confirms to B. cocophilus as the causal agent of red ring disease on oil palms in the study area. For our knowledge, this study reports the first partial sequences of segment D2-D3 of B. cocophilus in oil palm in Colombia.
RESUMO
Three populations, two from Colombia and one from Brazil, of Rotylenchulus reniformis associated with banana and plantain, were characterized using morphological, morphometric, and molecular methods. Morphometric data from these populations were similar to type and reference populations of R. reniformis. Partial sequences of both D2-D3 rDNA and mitochondrial cytochrome oxidase subunit I (COI) regions had a strong affinity (99% similarity) to previously published sequences of R. reniformis. Phylogenetic analyses (maximum likelihood and Bayesian inference) suggested that the Colombian populations of R. reniformis corresponded to the previously described Type A of the species. This is the definitive first report in Colombia of R. reniformis associated with banana and plantain crops.
