Root-knot nematodes, Meloidogyne spp., and the root-lesion nematode, Pratylenchus brachyurus, are the most common phytoparasites in soybean crop, which usually occur in association in crop areas. However, few studies were conducted on the interaction between these parasites. Therefore, this study aimed to assess the interference of the increase in M. javanica population in the reproduction of P. brachyurus, and the effect of mixed populations on soybean (cultivar BRS/MT Pintado) development. The experiment consisted in inoculating a population of 1000 specimens of P. brachyurus per plant Fontana, L.F.; Arieira, c.r.d.; Abe1, V.H.F.; Severino, J.J.; Arieira, J.O.; Monteiro, R.N.F. Interference of Meloidogyne javanica in the reproduction of Pratylenchus brachyurus in soybean cultivar BRS/MT pintado. Summa Phytopathologica, v.44, n.2, p.143-147, 2018. and changing the inoculum level of M. javanica, using zero, 1000, 2000 and 4000 eggs, in two different periods. After 65 days of inoculation, the increase in the initial population of M. javanica reduced by 79 and 73% the final population of P. brachyurus in the different experiments. However, both species significantly increased their populations. When subjected to the same inoculum level, M. javanica was more efficient in reproducing than P. brachyurus. The increase in the number of nematodes reduced the vegetative growth of the plant. Keywords: Glycine max, interactions, root-knot nematodes, root-lesion nematodes, mixed populationsSoybean is the most important oilseed crop in the world and has increased in percentage more than the major grain crops, particularly because its market has obtained a solid structure worldwide, the plant has been recognized as an important source of vegetable protein and technology has been generated, allowing the crop expansion to different regions of the world (17).Although soybean planted areas and productivity have continuously grown, maximum yield potential (4000 kg/ha) is hard to obtain in most countries. The main factors that limit the yield, the profitability and the success of soybean production are diseases, including nematodes which cause significant losses to the Brazilian production, varying from slight to complete (100%) (2, 11).Species of Meloidogyne, particularly Meloidogyne javanica (Treub) Chitwood and M. incognita (Kofoid and White) Chitwood, represent a serious problem in soybean producing regions (18). Data on specific yield losses caused by these two species are common and vary among the different crop areas or regions (1), reaching up to 40% in low fertility sandy soils.Another nematode that has a significant impact on Brazilian soybean production is Pratylenchus brachyurus (Godfrey) Filipjev and Schuurmans Stekhoven. It is an aggressive species that heavily infest soybean producing areas (5, 18). Crop losses caused by this nematode are estimated to range from 10 to 30% of the production potential, especially in areas showing sandy soil and irregular rainfall distribution (5). Nevertheless, declines of u...
The objective of this study was to evaluate the efficacy of the active ingredient abamectin, either in isolation or in combination with fungicides and insecticides formulated for the industrial seed treatment, on the population of Meloidogyne javanica, tested under greenhouse and in vitro conditions. In both tests, the combination of the following treatments was assessed: abamectin; thiamethoxam; fludioxonil + metalaxyl-M + thiabendazole. Water was used as control for the in vitro assay, whereas under greenhouse conditions, controls were inoculated and not inoculated with M. javanica. The tests were conducted in a completely randomized design with six (in vitro) and ten (greenhouse) replicates. For in vitro studies the effect on hatching, motility, and mortality of juveniles of M. javanica was evaluated. Under greenhouse conditions, the soybean 'BRS 133' seeds were treated, and at 15, 30, and 60 days after inoculation (DAI) with M. javanica, plant measurements were recorded. The penetration of second stage juveniles (J2) was also evaluated at 15 DAI. At 30 DAI, galls, egg masses, nematodes/g of root, and final population were evaluated. At 60 DAI, the final population of nematodes in the roots was quantified. The treatments containing abamectin were the most effective in diminishing the hatching of juveniles. All treatments had an effect on nematode motility when compared to the control, and in the treatment containing only abamectin, total juvenile mortality was observed. In greenhouse conditions, at 15 DAI, the treated soybean plants had the highest root mass and shoot length, differing statistically from the inoculated control. All treatments reduced the number of nematodes per gram of root, differing from the control. At 30 DAI, treatment efficiency was observed in reducing the final population of M. javanica, particularly the treatments using abamectin, and abamectin + thiamethoxam + fludioxonil + metalaxyl-M + thiabendazole. However, at 60 DAI, the effect of the treatments on the population of M. javanica did not persist. Key words: Hatching. Mortality. Motility. Nematicide. Root-knot nematode. ResumoO objetivo do trabalho foi avaliar a eficiência do ingrediente ativo abamectina, isolado ou em combinação com fungicidas e inseticidas formulados para o tratamento industrial de sementes, sobre a população de Meloidogyne javanica, in vitro e em casa de vegetação. Em ambos os ensaios, avaliou-se a combinação dos tratamentos: abamectina; thiamethoxam; fludioxonil + metalaxil-m + tiabendazol. Como controle utilizou-se água para o ensaio in vitro, e testemunhas inoculada e não inoculada com M. javanica, em casa de vegetação. Os ensaios foram realizados em delineamento inteiramente casualizado
Root-knot nematodes, genus Meloidogyne spp., are among the most destructive parasites of cultivated plants. The characteristic symptom of this disease is gall formation in the root system. Genetic resistance is one of the most efficient and economic methods of minimal environmental impact to control this endoparasite, and gall index has been used to select resistant varieties. However, this method is based on visual assessment of galls and is therefore a time-consuming and error-prone technique. Thus, this study aims to develop an automated computational method for Meloidogyne javanica gall counting. The proposed method was composed of five steps: visual counting of galls, image acquisition by a scanner, optimization of parameters based on the image group and image counting. Lettuce root showed the best results, with 1% mean relative error, while tomato root had the worst result, showing 32% mean relative error. The mean relative error for all tested roots was 13%.
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