ABSTRACT Integrated management is considered the best strategy to mitigate the damage caused by plant-parasitic nematodes. However, there is still limited information regarding some integrated techniques. Thus, this study aimed to assess the effects of genetic management associated with chemical control of Meloidogyne javanica in soybean (Glycine max (L.) Merr.) The experiment was installed in a greenhouse according to an 8×4 factorial design with eight replicates. The first factor was soybean cultivar (HO Juruena IPRO, resistant; Foco IPRO, HO Maracaí IPRO, and CZ 58B28 IPRO, moderately resistant; HO Mamoré IPRO, moderately susceptible; and Extrema IPRO, CZ 48B32 IPRO, and HO Aporé IPRO, susceptible). The second factor consisted of an untreated control and commercial nematicides based on abamectin, thiodicarb+imidacloprid, and fluopyram. Plants were inoculated with 2000 nematode eggs, and nematode and vegetative variables were evaluated at 65 d after inoculation. There was an interaction effect on nematode variables. Furthermore, there was an additive effect of genetic management and chemical control, mainly in resistant cultivars treated with thiodicarb+imidacloprid or fluopyram with controls of up to 69.90% and 96.86%, respectively. The application of fluopyram and the use of ‘HO Juruena IPRO’, ‘Foco IPRO’, or ‘HO Maracaí IPRO’ also contributed to the control of M. javanica. Vegetative variables were studied by analyzing product effects separately, but results were inconclusive.

ABSTRACT Nematodes of the Meloidogyne genus are among the main limiting factors of world agricultural productivity. Its management is quite complex and alternative methods such as the use of extracts have been widely studied. This study aimed to evaluate the penetration and development of M. javanica in soybean (Glycine max (L.) Merr.) treated with Ascophyllum nodosum extract and assess this algal product and its nutrient components in nematode management. Experiment 1 comprised five sampling times (5, 10, 15, 20, and 25 d after nematode inoculation) and three application methods (planting hole, foliar spraying, and untreated control). Soybean plants were inoculated with 2000 eggs+second-stage juveniles of M. javanica and treated with algal extract. Total nematode number, number of nematodes per developmental stage, and population density (nematodes g-1 root) were determined. Experiment 2 consisted of 11 treatments: Algal extract, N, K, P, Ca, Mg, Cu, Zn, Mn, Fe, combined nutrients, and untreated control. Soybean crops were evaluated for total nematode number, population density, gall index, plant height, root fresh weight, shoot fresh weight, and shoot dry weight. In Experiment 1, algal extract reduced nematode penetration, regardless of application method. There was a decrease in the total number of nematodes and number of nematode g-1 root by 83% and 56% in the application via furrow and 68% and 70% via foliar application, respectively. In Experiment 2, all nutrient treatments reduced at least one nematode parameter, with P, Ca, Mg, Fe, and combined nutrients (Trial 1) and algal extract, P, Ca, Mg, Cu, Zn, Mn, Fe and combined nutrients (Trial 2) achieving 83% to 95% reductions in population density. Nutrient treatments positively influenced vegetative development, as a 20% increase in height for the nutrients A. nodosum, N, K, P, Ca, Mg, Cu and Fe. Ascophyllum nodosum and its nutrient components have potential in the management of M. javanica in soybean.

ABSTRACT The use of non-host cover crops is a key strategy for controlling root-knot nematodes in infested fields. However, pathogenicity of nematodes to cover crops may vary between populations and localities. This study assessed the response of green manure species and millet (Pennisetum glaucum (L.) R.Br.) cultivars to four populations of Meloidogyne javanica (denominated Mj-2, Mj-3, Mj-6 and Mj-7). Seedlings of radish (Raphanus sativus L.), pigeon pea (Cajanus cajan (L.) Huth) ‘IAPAR 43’, buckwheat (Fagopyrum esculentum Moench) ‘IPR 92-Altar’ and millet ‘BRS 1501’, ‘ADR 300’ and ‘ADR 500’ were inoculated with 1000 eggs and second-stage juveniles of M. javanica. Soybean (Glycine max (L.) Merr.) ‘M6210 IPRO’ was used as control. At 60 d after inoculation, plants were evaluated for root fresh weight, gall index (GI), number of nematodes per gram of root and reproduction factor (RF). For GI, Mj-3 and Mj-6 were the most aggressive to soybean (GI = 5.0). In pigeon pea, Mj-7 resulted in the highest GI (3.5). Radish had the lowest GI (0.67) with Mj-2. For buckwheat, Mj-3 was the most aggressive population, with a GI of 4.50. Mj-3 and Mj-7 resulted in the highest GI in ‘ADR 300’, and Mj-6 and Mj-7 in ‘ADR 500’. The reproductive ability of nematode populations differed between hosts. Mj-2 was the most pathogenic to ‘ADR 300’ (RF = 10.88), Mj-3 to buckwheat (RF = 53.46) and radish (RF = 4.81), Mj-6 to ‘ADR 500’ (RF = 19.58) and Mj-7 to pigeon pea (RF = 2.99) and ‘BRS 1501’ (RF = 15.05). Soybean was susceptible to all M. javanica populations (RF = 33.69 to 257.22). Green manure species and millet cultivars varied in their responses to M. javanica populations of different origins.

RESUMO Os nematoides-das-galhas, gênero Meloidogyne spp., estão entre os parasitas mais destrutivos das plantas cultivadas. O sintoma mais característico da doença é o surgimento de galhas no sistema radicular. O uso da resistência genética é um dos mais eficientes, econômicos e menos impactantes do ponto de vista ambiental no controle desse endoparasita, sendo o índice de galhas uma das metodologias utilizadas para seleção de variedades resistentes. No entanto, é um método baseado na avaliação visual de galhas e, portanto, é uma técnica que exige tempo e é passiva de erros. Assim, este trabalho tem como objetivo desenvolver um método computacional automatizado para contar as gralhas de Meloidogyne javanica. O método proposto foi composto de cinco etapas: uma contagem humana visual de galhas, a aquisição de imagens de um scanner, otimização de parâmetros com base no conjunto de imagens e, finalmente, contagem das imagens. A raiz da alface produziu os melhores resultados, com 1% de erro relativo médio e a raiz do tomate o pior, com erro relativo médio de 32%. O erro relativo médio para todas as raízes testadas foi de 13%.

ABSTRACT 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%.