Survey of nematodes associated with sugarcane in the state of Paraná, Brazil

Sugarcane-associated nematodes (Saccharum spp.) can reduce productivity up to 50%. Through the survey, it was possible to identify the main nematodes that occur in a certain region as a tool for designing the best management and control strategies. The aim of this study was to characterize the population of nematodes associated with sugarcane in the North Central, North Pioneiro and Northwest mesoregion of the state of Paraná, Brazil, quantify the nematode genera associated with the crop and identify the species of Pratylenchus and Meloidogyne. A total amount of 89 soil and root composite samples were collected in nine municipalities. Nematodes were extracted and counted in a Peters counting chamber under an optical light microscope. Morphological description followed identification keys. Pratylenchus spp. were identified by morphological characteristics; Meloidogyne spp. were identified by morphological characteristics and isoenzyme electrophoresis. Twelve genera of nematodes associated with sugarcane were identified: Pratylenchus, Meloidogyne, Helicotylenchus, Xiphinema, Mesocriconema, Trichodorus, Aphelenchus, Hoplolaimus, Tylenchus, Tylenchorhynchus, Ditylenchus, and Paratrichodorus. The genera Pratylenchus and Meloidogyne were found with the highest frequencies in the roots. Among the species of Pratylenchus, P. zeae and P. brachyurus were found, with P. zeae being the most frequent. Among the Meloidogyne species, only M. javanica was found. These results are essential to aid decision making in the management of phytonematodes, mainly in the development of new control strategies and in directing genetic breeding programs for development of sugarcane cultivars for the Paraná state.

Nitrogen and potassium synergism influences the yield and quality of Dioscorea cayennensis / Sinergismo de nitrogênio e potássio influencia na produtividade e qualidade de Dioscorea cayennensis

This study aimed to evaluate yield, quality, nematode incidence, chlorophyll content, and primary foliar macronutrients of yam in response to nitrogen and potassium fertilization. A complete randomized block design was used in a factorial scheme (5 x 5), with five nitrogen (0; 60; 120; 180 and 240 kg ha-1 of N) and five potassium doses (0; 60; 120; 180 and 240 kg ha-1 of K2O), with four replicates. The mass, total and commercial productivity of tubers, starch content, ash, leaf N, P, and K content, chlorophyll, and nematode incidence were evaluated. The average mass of tubers obtained was 1.935 kg with doses of 133 kg ha-1 of N and 105 kg ha-1 of K2O. The dose of 178 kg ha-1 of N promoted maximum total tuber productivity (22.56 t ha-1). The doses of 132 kg ha-1 of N and 118 kg ha-1 of K2O resulted in maximum productivity of commercial tubers with 20.35 t ha-1. Leaf N and K, starch, and ash contents were within the standards for yam. The incidence of Meloidogyne, Scutellonema, and Pratylenchus reduced with the increasing simple effect doses of N and K2O. The maximum chlorophyll content was obtained at the dose of 240 kg ha-1 of N. The nitrogen and potassium interaction, despite the antagonistic effects on the accumulation of foliar P and starch, increased the productivity and average mass of commercial tubers, consequently ensuring the profitability of yam cultivation.

Objetivou-se avaliar a produtividade, qualidade, incidência de nematoides, teor de clorofila e macronutrientes primários foliares do inhame em função das doses de nitrogênio e potássio. O delineamento experimental de blocos casualizados foi utilizado em esquema fatorial (5 x 5), com cinco doses de nitrogênio (0; 60; 120; 180 e 240 kg ha-1 de N), e cinco doses de potássio (0; 60; 120; 180 e 240 kg ha-1 de K2O), com quatro repetições. As características avaliadas foram à massa média, produtividade total e comercial de túberas, teor de amido, cinzas, teor de N, P e K foliar, clorofila e a incidência de nematoides. A massa média de túberas foi de 1,935 kg com uso de 133 kg ha-1 de N e 105 kg ha-1 de K2O. A dose de 178 kg ha-1 de N proporcionou máxima produtividade total de túberas (22,56 t ha-1). As doses de 132 kg ha-1 de N e 118 kg ha-1 de K2O, foram responsáveis pela produtividade máxima de túberas comerciais de 20,35 t ha-1. Os teores de N e K foliar, amido e cinzas ficaram dentro padrão para o inhame. A incidência de Meloidogyne, Scutellonema e Pratylenchus foram reduzidas com aumento das doses de efeito simples de N e K2O. A clorofila máxima foi observada na dose de 240 kg ha-1 de N. A interação nitrogênio e potássio apesar dos efeitos antagônicos sobre o acúmulo de P foliar e amido, promove aumento da produtividade e massa média de túberas comerciais, consequentemente, garante a rentabilidade do cultivo de inhame.

Phytonematodes infesting common bean fields in Brazil, and pathogenicity tests with Pratylenchus brachyurus

ABSTRACT Phytonematodes are among the main pathogens of the common bean. In general, control practices that aim to control these pathogens have not been regularly adopted in Brazil. The objectives of the present study were to evaluate the occurrence of phytonematodes in dry bean fields in Paraná and São Paulo states and estimate the pathogenicity of Pratylenchus brachyurus to dry bean in glasshouse experiments. Root and soil were sampled for nematode extraction, identification and estimation of population density. Four glasshouse experiments with different initial population densities were carried out to evaluate the effect of P. brachyurus on the growth of dry bean plants. Six species of phytonematodes were detected, namely Helicotylenchus dihystera, P. brachyurus, Pratylenchus crenatus, Meloidogyne javanica, Meloidogyne incognita and Rotylenchulus sp. The spiral nematode H. dihystera was found in all samples and was the most abundant species in both states. The lesion nematode P. brachyurus was also frequent, reaching 94% in Paraná and 100% in São Paulo. The root-knot nematodes and Rotylenchulus sp. were reported only in São Paulo fields (45% and 18% frequency, respectively), and P. crenatus only in Paraná (12%). The most abundant nematode in the soil was H. dihystera, and in roots was P. crenatus. It was demonstrated that densities of 6.66 specimens of P. brachyurus per cm3 of soil provoke visible and measurable root decay. In conclusion, survey data showed low phytonematode densities and pathogenicity tests demonstrated that densities above 6.67 specimens of P. brachyurus per cm3 of soil cause damage to the dry bean roots.

Host status of eucalypt species to Pratylenchus brachyurus and Meloidogyne incognita

ABSTRACT Plant parasitic nematodes are major threats to Brazilian and world agriculture. Among them, Pratylenchus brachyurus and Meloidogyne incognita stand out as major pests for several crops, including corn, cotton, soybean among others, which can be components of integrated crop-livestock-forestry systems (ICLFs). In this context, information about the host status of eucalypts (Corymbia spp. and Eucalyptus spp.) to plant parasitic nematodes becomes more relevant in Brazil, due to the use of eucalypts in ICLFs. If tree components used on this system increase the population density of P. brachyurus and M. incognita, it is possible that these pathogens could damage shorter-cycle crops. Since information about the host status of eucalypts to plant parasitic nematodes is scarce, this study evaluated the host status of some eucalypt species to P. brachyurus and M. incognita. Two greenhouse trials were done to evaluate the reproduction of P. brachyurus and one to M. incognita, using some of the most cultivated species and hybrids of eucalypts in Brazil. The population growth of P. brachyurus increased on Corymbia citriodora, Eucalyptus grandis, Eucalyptus dunnii × Eucalyptus urophylla, and E. grandis × E. urophylla after ~90 days of inoculation. Conversely, despite M. incognita reproducing well in the control plants, no individuals were recovered from C. citriodora, E. urophylla and E. grandis × E. urophylla, which were classified as resistant plants. Based on both obtained and available data, M. incognita poses no threat to eucalypt species today. However, P. brachyurus is suggested to be a threat to eucalypts.

Phytonematodes infesting common bean fields in Brazil, and pathogenicity tests with Pratylenchus brachyurus

Phytonematodes are among the main pathogens of the common bean. In general, control practices that aim to control these pathogens have not been regularly adopted in Brazil. The objectives of the present study were to evaluate the occurrence of phytonematodes in dry bean fields in Paraná and São Paulo states and estimate the pathogenicity of Pratylenchus brachyurus to dry bean in glasshouse experiments. Root and soil were sampled for nematode extraction, identification and estimation of population density. Four glasshouse experiments with different initial population densities were carried out to evaluate the effect of P. brachyurus on the growth of dry bean plants. Six species of phytonematodes were detected, namely Helicotylenchus dihystera, P. brachyurus, Pratylenchus crenatus, Meloidogyne javanica, Meloidogyne incognita and Rotylenchulus sp. The spiral nematode H. dihystera was found in all samples and was the most abundant species in both states. The lesion nematode P. brachyurus was also frequent, reaching 94% in Paraná and 100% in São Paulo. The root-knot nematodes and Rotylenchulus sp. were reported only in São Paulo fields (45% and 18% frequency, respectively), and P. crenatus only in Paraná (12%). The most abundant nematode in the soil was H. dihystera, and in roots was P. crenatus. It was demonstrated that densities of 6.66 specimens of P. brachyurus per cm3 of soil provoke visible and measurable root decay. In conclusion, survey data showed low phytonematode densities and pathogenicity tests demonstrated that densities above 6.67 specimens of P. brachyurus per cm3 of soil cause damage to the dry bean roots.

Host status of eucalypt species to Pratylenchus brachyurus and Meloidogyne incognita

Plant parasitic nematodes are major threats to Brazilian and world agriculture. Among them, Pratylenchus brachyurus and Meloidogyne incognita stand out as major pests for several crops, including corn, cotton, soybean among others, which can be components of integrated crop-livestock-forestry systems (ICLFs). In this context, information about the host status of eucalypts (Corymbia spp. and Eucalyptus spp.) to plant parasitic nematodes becomes more relevant in Brazil, due to the use of eucalypts in ICLFs. If tree components used on this system increase the population density of P. brachyurus and M. incognita, it is possible that these pathogens could damage shorter-cycle crops. Since information about the host status of eucalypts to plant parasitic nematodes is scarce, this study evaluated the host status of some eucalypt species to P. brachyurus and M. incognita. Two greenhouse trials were done to evaluate the reproduction of P. brachyurus and one to M. incognita, using some of the most cultivated species and hybrids of eucalypts in Brazil. The population growth of P. brachyurus increased on Corymbia citriodora, Eucalyptus grandis, Eucalyptus dunnii × Eucalyptus urophylla, and E. grandis × E. urophylla after ~90 days of inoculation. Conversely, despite M. incognita reproducing well in the control plants, no individuals were recovered from C. citriodora, E. urophylla and E. grandis × E. urophylla, which were classified as resistant plants. Based on both obtained and available data, M. incognita poses no threat to eucalypt species today. However, P. brachyurus is suggested to be a threat to eucalypts.

Spectral detection of nematodes in soybean at flowering growth stage using unmanned aerial vehicles / Detecção espectral de nematóides na soja em estádio de florescimento por meio de veículos aéreos não-tripulados

Soybean is one of the main crop species grown in the world. However, there is a decline in productivity due to the various types of stress, including the nematodes Heterodera glycines and Pratylenchus brachyurus. The objectives were to determine the best spectral band for detecting H. glycines and P. brachyurus at the beginning of flowering (R1). Soil and root sampling was conducted at nine sampling sites in each of the five nematode-infested regions, totaling 45 sampling points. Flights were made at all regions using Phantom 4 Advanced, Sequoia and 14-band customized Sentera. For H. glycines, the red spectral band best explained the variability on soil and root nematode counts as well as the second stage of juveniles in soil. For P. brachyurus, Sentera RedEdge best explained the variability in root nematode counts and Sequoia NIR best explained soil juveniles. A multiple linear regression model using spectral data for detecting P. brachyurus and H. glycines improved R² compared to simple linear regressions. At flowering growth stage (R1), soybean spectral reflectance was associated with the number of H. glycines and P. brachyurus on soil and roots using low-cost and multispectral sensors.(AU)

A soja é uma das principais espécies de planta cultivadas no mundo. Todavia, perdas de produtividade são ocasionadas por vários tipos de estresses, incluindo os nematoides H. glycines e P. brachyurus. Como objetivo, buscou-se determinar a melhor banda espectral para a detecção do H. glycines e P. brachyurus com o uso de modelos de regressões lineares simples e definir um modelo matemático de regressão linear múltiplo para sua detecção, no início do florescimento (R1). Para isto, foram definidos nove pontos de coleta em cinco reboleiras, totalizando 45 pontos. As coletas foram feitas em um padrão específico de distâncias, de forma a ter amostras com tipos variados de populações de nematoides. Foram realizados voos com o Phantom 4 Advanced, Sequoia e Sentera sobre cada uma das reboleiras. O comprimento de onda do vermelho melhor explicou a variabilidade dos dados para H. glycines no solo e na raiz, bem como dos juvenis de segundo estádio no solo. Para P. brachyurus, a RedEdge da Sentera foi a que explicou melhor a variabilidade dos dados para nematoide na raiz e a NIR da Sequoia a que melhor explicou para juvenis no solo. Quando se utilizou um modelo matemático para a detecção do P. brachyurus e H. glycines, percebe-se uma grande melhora no R² e p-valor com relação às regressões lineares simples. No início da floração (R1), a refletância espectral da soja foi associada ao número de H. glycines e P. brachyurus no solo e nas raízes, usando sensores de baixo custo e multiespectrais.(AU)

Crotalaria species in succession to soybean for the management of Pratylenchus brachyurus / Espécies de crotalaria em sucessão à soja para o manejo de Pratylenchus brachyuru

Soybean is the main agricultural crop in the State of Mato Grosso do Sul, Brazil. It is primarily cultivated in a crop succession system, in wich soybean is grown in spring/summer, followed by corn or graminaceous pastures in autumn/winter as a second crop. Due to the intensive cultivation, new phytosanitary problems have arisen, among them the root-lesion nematode, Pratylenchus brachyurus, which besides causing damage to plant roots, can be important gateway for other soil pathogens. The recent occurrence of high nematode population densities has brought great concern due to the limited resistant soybean genotypes available. Besides, the use of nematicides only reduces nematodes populations temporarily. A viable alternative for the control of soil nematodes could be the use of Crotalaria spp. in succession or rotation with soybean. Crotalaria is immune or a bad host to the nematode, besides having high capacity of biological nitrogen fixation. Thus, the objective of the present research was to define the best way of insertion of this legume as a second crop in soybean production systems to reduce the population density of the root-lesion nematode. Two experiments were carried out: one in the field, in an infested area, and other in a greenhouse. In both experiments, the treatments were: 1) Zea mays, 2) Brachiaria brizantha cv. Xaraés,, 3) Z. mays + Crotalaria spectabilis, 4) Z. mays + C. ochroleuca, 5) B. brizantha cv. Xaraés + C. spectabilis, 6) B. brizantha cv. Xaraés + C. ochroleuca, 7) C. spectabilis, and 8) C. ochroleuca. The effect of the treatments was evaluated by estimating the number of nematodes in the roots of autumn/winter crops, as well as in the roots of the soybean cultivated in the sequence. The cultivation of both Crotalaria species provided suppression of the nematode population. However, when intercropped with corn or Xaraés palisade grass, the suppressive effect of Crotalaria was supplanted by corn and Xaraés palisadegrass susceptibility to the root-lesion nematode.(AU)

A soja é a principal cultura agrícola explorada no Estado do Mato Grosso do Sul, cultivada prioritariamente no sistema de sucessão com milho safrinha. Com expansão da cultura, novos problemas fitossanitários surgiram, como o nematoide das lesões radiculares, Pratylenchus brachyurus. A ocorrência recente de altas densidades populacionais do nematoide trouxe preocupação pela limitada quantidade de genótipos de soja resistentes e o uso de nematicidas reduzir temporariamente a população. Uma alternativa viável para controle seria o uso de crotalária em sucessão ou rotação com a soja, pois esta é má hospedeira ou imune a nematoides. Assim, o objetivo do presente trabalho foi definir a melhor forma de inserção dessa leguminosa em sucessão com soja para redução da densidade populacional do Pratylenchus brachyurus. O trabalho consistiu de dois experimentos: à campo, em uma área infestada, e em casa de vegetação. Os tratamentos utilizados em ambos experimentos foram: 1) Zea mays, 2) Brachiaria brizantha cv. Xaraés, 3) Z. mays + Crotalaria spectabilis, 4) Z. mays + C. ochroleuca, 5) Xaraés + C. spectabilis, 6) Xaraés + C. ochroleuca, 7) C. spectabilis, 8) C. ochroleuca. O efeito dos tratamentos sobre densidade populacional do nematoide foi avaliado por: estimativa do número de nematoides nas raízes; cálculo da variação da população durante todo o experimento; fator de reprodução e; características fitotécnicas. O cultivo das espécies de Crotalaria, sem consorciação, proporcionaram supressão da população dos nematoides. Todavia o efeito supressor das crotalárias consorciadas foi suplantado pela suscetibilidade do milho e Xaraés ao Pratylenchus brachyurus.(AU)

Host suitability of grain sorghum and sudangrass for Pratylenchus brachyurus

ABSTRACT: Nowadays, the root-lesion nematode Pratylenchus brachyurus (Godfrey) is a major pest of soybean in Brazil, mainly in areas using double cropping with maize or cotton, which are suitable hosts for P. brachyurus. A great effort has been made to find cash crops for P. brachyurus management. Grain sorghum [Sorghum bicolor (L.)] was classified as a non-host for P. brachyurus but based on a single trial. It would be a valuable option as a culture for double cropping with soybean, as it is profitable and can be used in root-lesion nematode management. Sudangrass (S. bicolor var. sudanense) is not directly profitable, but Brazilian farmers favor it because it can produce pasture, green chop, silage, or hay under unfavorable hydric conditions. However, no information is available regarding the suitability of sudangrass for P. brachyurus. Thus, the current study aimed to assess the suitability of grain sorghum and sudangrass for P. brachyurus in two glasshouse trials. The first trial tested sudangrass and grain sorghum DKB 510, Dow 740, Dow 822, DKB 599, and AG 1040. The second trial retested sudangrass and grain sorghum Dow 740 and DKB 599. The results demonstrated that sudangrass and grain sorghum were suitable hosts for P. brachyurus. These results, in addition to those obtained for other types of sorghum, emphasize that S. bicolor and sudangrass should be avoided in fields infested with P. brachyurus, as they increase the nematode population.

RESUMO: Atualmente, o nematoide das lesões radiculares Pratylenchus brachyurus Godfrey é um dos principais patógenos para a soja no Brasil, principalmente em áreas com sucessão de milho ou algodão, que também são suscetíveis a P. brachyurus. Grandes esforços têm sido feitos a fim de encontrar uma cultura rentável que possa ser utilizada no manejo de P. brachyurus. O sorgo granífero (Sorghum bicolor L.) é relatado como resistente a P. ­brachyurus, porém com base em apenas um ensaio. Adicionalmente, o capim-sudão (S. ­bicolor var. sudanense) não é diretamente rentável, mas é apreciado pelos agricultores brasileiros por produzir pasto, material verde picado, silagem ou feno, mesmo sob condições hídricas desfavoráveis. Entretanto, não há nenhuma informação sobre a suscetibilidade dessa cultura a P. brachyurus. Dentro desse contexto, o objetivo do presente trabalho foi avaliar a suscetibilidade de cultivares de sorgo granífero e capim-sudão a P. brachyurus em dois ensaios em casa de vegetação. No primeiro experimento, foram testados o capim-sudão e os sorgos graníferos DKB 510, Dow 740, Dow 822, DKB 599 e AG 1040. No segundo experimento, capim-sudão e os cultivares de sorgo granífero Dow 740 e DKB 599 foram testados novamente. Os resultados de ambos os ensaios demonstraram que o capim-sudão e o sorgo granífero são suscetíveis a P. ­brachyurus. Esses resultados, mais os obtidos para outros tipos de sorgo, demonstram que S. ­bicolor e o capim-sudão devem ser evitados em áreas infestadas com P. ­brachyurus, já que essas culturas aumentam dramaticamente as densidades populacionais do nematoide das lesões no solo.

Host suitability of grain sorghum and sudangrass for Pratylenchus brachyurus

ABSTRACT: Nowadays, the root-lesion nematode Pratylenchus brachyurus (Godfrey) is a major pest of soybean in Brazil, mainly in areas using double cropping with maize or cotton, which are suitable hosts for P. brachyurus. A great effort has been made to find cash crops for P. brachyurus management. Grain sorghum [Sorghum bicolor (L.)] was classified as a non-host for P. brachyurus but based on a single trial. It would be a valuable option as a culture for double cropping with soybean, as it is profitable and can be used in root-lesion nematode management. Sudangrass (S. bicolor var. sudanense) is not directly profitable, but Brazilian farmers favor it because it can produce pasture, green chop, silage, or hay under unfavorable hydric conditions. However, no information is available regarding the suitability of sudangrass for P. brachyurus. Thus, the current study aimed to assess the suitability of grain sorghum and sudangrass for P. brachyurus in two glasshouse trials. The first trial tested sudangrass and grain sorghum DKB 510, Dow 740, Dow 822, DKB 599, and AG 1040. The second trial retested sudangrass and grain sorghum Dow 740 and DKB 599. The results demonstrated that sudangrass and grain sorghum were suitable hosts for P. brachyurus. These results, in addition to those obtained for other types of sorghum, emphasize that S. bicolor and sudangrass should be avoided in fields infested with P. brachyurus, as they increase the nematode population.

RESUMO: Atualmente, o nematoide das lesões radiculares Pratylenchus brachyurus Godfrey é um dos principais patógenos para a soja no Brasil, principalmente em áreas com sucessão de milho ou algodão, que também são suscetíveis a P. brachyurus. Grandes esforços têm sido feitos a fim de encontrar uma cultura rentável que possa ser utilizada no manejo de P. brachyurus. O sorgo granífero (Sorghum bicolor L.) é relatado como resistente a P. ­brachyurus, porém com base em apenas um ensaio. Adicionalmente, o capim-sudão (S. ­bicolor var. sudanense) não é diretamente rentável, mas é apreciado pelos agricultores brasileiros por produzir pasto, material verde picado, silagem ou feno, mesmo sob condições hídricas desfavoráveis. Entretanto, não há nenhuma informação sobre a suscetibilidade dessa cultura a P. brachyurus. Dentro desse contexto, o objetivo do presente trabalho foi avaliar a suscetibilidade de cultivares de sorgo granífero e capim-sudão a P. brachyurus em dois ensaios em casa de vegetação. No primeiro experimento, foram testados o capim-sudão e os sorgos graníferos DKB 510, Dow 740, Dow 822, DKB 599 e AG 1040. No segundo experimento, capim-sudão e os cultivares de sorgo granífero Dow 740 e DKB 599 foram testados novamente. Os resultados de ambos os ensaios demonstraram que o capim-sudão e o sorgo granífero são suscetíveis a P. ­brachyurus. Esses resultados, mais os obtidos para outros tipos de sorgo, demonstram que S. ­bicolor e o capim-sudão devem ser evitados em áreas infestadas com P. ­brachyurus, já que essas culturas aumentam dramaticamente as densidades populacionais do nematoide das lesões no solo.

Host suitability of grain sorghum and sudangrass for Pratylenchus brachyurus / Suscetibilidade do sorgo granífero e capim-sudão a Pratylenchus brachyurus

Nowadays, the root-lesion nematode Pratylenchus brachyurus (Godfrey) is a major pest of soybean in Brazil, mainly in areas using double cropping with maize or cotton, which are suitable hosts for P. brachyurus. A great effort has been made to find cash crops for P. brachyurus management. Grain sorghum [Sorghum bicolor (L.)] was classified as a non-host for P. brachyurus but based on a single trial. It would be a valuable option as a culture for double cropping with soybean, as it is profitable and can be used in root-lesion nematode management. Sudangrass (S. bicolor var. sudanense) is not directly profitable, but Brazilian farmers favor it because it can produce pasture, green chop, silage, or hay under unfavorable hydric conditions. However, no information is available regarding the suitability of sudangrass for P. brachyurus. Thus, the current study aimed to assess the suitability of grain sorghum and sudangrass for P. brachyurus in two glasshouse trials. The first trial tested sudangrass and grain sorghum 'DKB 510', 'Dow 740', 'Dow 822', 'DKB 599', and 'AG 1040'. The second trial retested sudangrass and grain sorghum 'Dow 740' and 'DKB 599'. The results demonstrated that sudangrass and grain sorghum were suitable hosts for P. brachyurus. These results, in addition to those obtained for other types of sorghum, emphasize that S. bicolor and sudangrass should be avoided in fields infested with P. brachyurus, as they increase the nematode population.(AU)

Atualmente, o nematoide das lesões radiculares Pratylenchus brachyurus Godfrey é um dos principais patógenos para a soja no Brasil, principalmente em áreas com sucessão de milho ou algodão, que também são suscetíveis a P. brachyurus. Grandes esforços têm sido feitos a fim de encontrar uma cultura rentável que possa ser utilizada no manejo de P. brachyurus. O sorgo granífero (Sorghum bicolor L.) é relatado como resistente a P. ­brachyurus, porém com base em apenas um ensaio. Adicionalmente, o capim-sudão (S. ­bicolor var. sudanense) não é diretamente rentável, mas é apreciado pelos agricultores brasileiros por produzir pasto, material verde picado, silagem ou feno, mesmo sob condições hídricas desfavoráveis. Entretanto, não há nenhuma informação sobre a suscetibilidade dessa cultura a P. brachyurus. Dentro desse contexto, o objetivo do presente trabalho foi avaliar a suscetibilidade de cultivares de sorgo granífero e capim-sudão a P. brachyurus em dois ensaios em casa de vegetação. No primeiro experimento, foram testados o capim-sudão e os sorgos graníferos DKB 510, Dow 740, Dow 822, DKB 599 e AG 1040. No segundo experimento, capim-sudão e os cultivares de sorgo granífero Dow 740 e DKB 599 foram testados novamente. Os resultados de ambos os ensaios demonstraram que o capim-sudão e o sorgo granífero são suscetíveis a P. ­brachyurus. Esses resultados, mais os obtidos para outros tipos de sorgo, demonstram que S. ­bicolor e o capim-sudão devem ser evitados em áreas infestadas com P. ­brachyurus, já que essas culturas aumentam dramaticamente as densidades populacionais do nematoide das lesões no solo.(AU)

Host suitability of grain sorghum and sudangrass for Pratylenchus brachyurus / Suscetibilidade do sorgo granífero e capim-sudão a Pratylenchus brachyurus

Nowadays, the root-lesion nematode Pratylenchus brachyurus (Godfrey) is a major pest of soybean in Brazil, mainly in areas using double cropping with maize or cotton, which are suitable hosts for P. brachyurus. A great effort has been made to find cash crops for P. brachyurus management. Grain sorghum [Sorghum bicolor (L.)] was classified as a non-host for P. brachyurus but based on a single trial. It would be a valuable option as a culture for double cropping with soybean, as it is profitable and can be used in root-lesion nematode management. Sudangrass (S. bicolor var. sudanense) is not directly profitable, but Brazilian farmers favor it because it can produce pasture, green chop, silage, or hay under unfavorable hydric conditions. However, no information is available regarding the suitability of sudangrass for P. brachyurus. Thus, the current study aimed to assess the suitability of grain sorghum and sudangrass for P. brachyurus in two glasshouse trials. The first trial tested sudangrass and grain sorghum 'DKB 510', 'Dow 740', 'Dow 822', 'DKB 599', and 'AG 1040'. The second trial retested sudangrass and grain sorghum 'Dow 740' and 'DKB 599'. The results demonstrated that sudangrass and grain sorghum were suitable hosts for P. brachyurus. These results, in addition to those obtained for other types of sorghum, emphasize that S. bicolor and sudangrass should be avoided in fields infested with P. brachyurus, as they increase the nematode population.(AU)

Atualmente, o nematoide das lesões radiculares Pratylenchus brachyurus Godfrey é um dos principais patógenos para a soja no Brasil, principalmente em áreas com sucessão de milho ou algodão, que também são suscetíveis a P. brachyurus. Grandes esforços têm sido feitos a fim de encontrar uma cultura rentável que possa ser utilizada no manejo de P. brachyurus. O sorgo granífero (Sorghum bicolor L.) é relatado como resistente a P. ­brachyurus, porém com base em apenas um ensaio. Adicionalmente, o capim-sudão (S. ­bicolor var. sudanense) não é diretamente rentável, mas é apreciado pelos agricultores brasileiros por produzir pasto, material verde picado, silagem ou feno, mesmo sob condições hídricas desfavoráveis. Entretanto, não há nenhuma informação sobre a suscetibilidade dessa cultura a P. brachyurus. Dentro desse contexto, o objetivo do presente trabalho foi avaliar a suscetibilidade de cultivares de sorgo granífero e capim-sudão a P. brachyurus em dois ensaios em casa de vegetação. No primeiro experimento, foram testados o capim-sudão e os sorgos graníferos DKB 510, Dow 740, Dow 822, DKB 599 e AG 1040. No segundo experimento, capim-sudão e os cultivares de sorgo granífero Dow 740 e DKB 599 foram testados novamente. Os resultados de ambos os ensaios demonstraram que o capim-sudão e o sorgo granífero são suscetíveis a P. ­brachyurus. Esses resultados, mais os obtidos para outros tipos de sorgo, demonstram que S. ­bicolor e o capim-sudão devem ser evitados em áreas infestadas com P. ­brachyurus, já que essas culturas aumentam dramaticamente as densidades populacionais do nematoide das lesões no solo.(AU)

Mobility of Pratylenchus coffeae in segmented soil columns submitted to water flows and plant stimuli / Mobilidade de Pratylenchus coffeae no solo em colunas segmentadas submetidas a fluxos de água e estímulos vegetais

The root-lesion nematode Pratylenchus spp. causes a high-severity disease, promoting high economic losses in various crops of agricultural importance. The nematode control is difficult, especially after introduction into the area. Studies on the migration of this parasite in the soil are scarce. However, understanding nematode behavior in the soil is fundamental to increase the efficiency of management practices, especially in irrigated agriculture. This study aimed to evaluate the influence of water flow and plant stimulus on Pratylenchus coffeae mobility in segmented soil columns. The columns were segmented into 11 rings of 1 cm long filled with washed sand, one of the ends exposed to a bait, and submitted to flows of 0, 3, 7 cm3/min of water. Baits for nematode attraction and repelling consisted of sectioned tubers of yam (Dioscorea cayennensis) and cut leaves of neem (Azadirachta indica), respectively, and the absence of baits as the control. Nematodes were injected into the central segment of the column, and migration and presence in water leaching were determined five days after soil infestation. Mobility of P. coffeae varied with water flow and bait type. In the absence of water flow, nematodes migrated in the opposite direction to the neem baits, but migration was well distributed in the presence of yam baits, with specimens present in all column segments. The nematode had significantly higher resistance to water flow of 3 cm3/min in the presence of yam baits. No nematodes were found in the water leached at flows of 3 and 7 cm3/min in the absence of bait.

O nematoide das lesões radiculares Pratylenchus spp. causa doença de alta severidade promovendo elevadas perdas econômicas em inúmeras culturas de importância agrícola. O controle é difícil, principalmente depois de sua introdução na área. Estudos sobre a migração desse parasito no solo são escassos. No entanto, entender o comportamento do nematoide no solo é fundamental para aumentar a eficiência das práticas de manejo, especialmente em agricultura irrigada. O objetivo do estudo foi avaliar a influência do fluxo de água e do estímulo vegetal na mobilidade de Pratylenchus coffeae em colunas de solo. As colunas foram segmentadas em 11 anéis de 1 cm de comprimento, preenchidas com areia lavada, tendo uma das extremidades exposta à isca e submetida a fluxos de 0, 3, 7 cm3/min de água. As iscas para atração e afastamento do nematoide consistiram de túberas seccionadas de inhame (Dioscorea cayennensis) e folhas picotadas de nim (Azadirachta indica), respectivamente, e a ausência de iscas como testemunha. Os nematoides foram injetados no segmento central da coluna e a migração e lixiviação determinadas cinco dias após infestação do solo. A mobilidade de P. coffeae variou com fluxo de água e tipo de isca. Na ausência de fluxo de água os nematoides migraram em sentido contrário às iscas de nim, mas a migração foi bem distribuída na presença de iscas de inhame, com espécimes presentes em todos os segmentos da coluna. Quando aplicado fluxo de 3 cm3/min de água, P.coffeae ofereceu significativamente maior resistência ao fluxo na presença de iscas de inhame. Os nematoides não foram lixiviados nos fluxos de 3 e 7 cm3/min de água na ausência de isca.

Mobility of Pratylenchus coffeae in segmented soil columns submitted to water flows and plant stimuli / Mobilidade de Pratylenchus coffeae no solo em colunas segmentadas submetidas a fluxos de água e estímulos vegetais

The root-lesion nematode Pratylenchus spp. causes a high-severity disease, promoting high economic losses in various crops of agricultural importance. The nematode control is difficult, especially after introduction into the area. Studies on the migration of this parasite in the soil are scarce. However, understanding nematode behavior in the soil is fundamental to increase the efficiency of management practices, especially in irrigated agriculture. This study aimed to evaluate the influence of water flow and plant stimulus on Pratylenchus coffeae mobility in segmented soil columns. The columns were segmented into 11 rings of 1 cm long filled with washed sand, one of the ends exposed to a bait, and submitted to flows of 0, 3, 7 cm3/min of water. Baits for nematode attraction and repelling consisted of sectioned tubers of yam (Dioscorea cayennensis) and cut leaves of neem (Azadirachta indica), respectively, and the absence of baits as the control. Nematodes were injected into the central segment of the column, and migration and presence in water leaching were determined five days after soil infestation. Mobility of P. coffeae varied with water flow and bait type. In the absence of water flow, nematodes migrated in the opposite direction to the neem baits, but migration was well distributed in the presence of yam baits, with specimens present in all column segments. The nematode had significantly higher resistance to water flow of 3 cm3/min in the presence of yam baits. No nematodes were found in the water leached at flows of 3 and 7 cm3/min in the absence of bait. (AU)

O nematoide das lesões radiculares Pratylenchus spp. causa doença de alta severidade promovendo elevadas perdas econômicas em inúmeras culturas de importância agrícola. O controle é difícil, principalmente depois de sua introdução na área. Estudos sobre a migração desse parasito no solo são escassos. No entanto, entender o comportamento do nematoide no solo é fundamental para aumentar a eficiência das práticas de manejo, especialmente em agricultura irrigada. O objetivo do estudo foi avaliar a influência do fluxo de água e do estímulo vegetal na mobilidade de Pratylenchus coffeae em colunas de solo. As colunas foram segmentadas em 11 anéis de 1 cm de comprimento, preenchidas com areia lavada, tendo uma das extremidades exposta à isca e submetida a fluxos de 0, 3, 7 cm3/min de água. As iscas para atração e afastamento do nematoide consistiram de túberas seccionadas de inhame (Dioscorea cayennensis) e folhas picotadas de nim (Azadirachta indica), respectivamente, e a ausência de iscas como testemunha. Os nematoides foram injetados no segmento central da coluna e a migração e lixiviação determinadas cinco dias após infestação do solo. A mobilidade de P. coffeae variou com fluxo de água e tipo de isca. Na ausência de fluxo de água os nematoides migraram em sentido contrário às iscas de nim, mas a migração foi bem distribuída na presença de iscas de inhame, com espécimes presentes em todos os segmentos da coluna. Quando aplicado fluxo de 3 cm3/min de água, P.coffeae ofereceu significativamente maior resistência ao fluxo na presença de iscas de inhame. Os nematoides não foram lixiviados nos fluxos de 3 e 7 cm3/min de água na ausência de isca.(AU)

Resistance to Pratylenchus brachyurus in Vitis species population through multivariate approaches and mixed models

Genetically diverse interspecific hybrids of Vitis were selected for resistance to Pratylenchus brachyurus. Three segregating populations with 57 hybrid crosses were evaluated. The parents included Vitis romanetiiC166-043 × 07355-075, 06354-047 × Cereza and 06354-047 × Nocera, selected from the germplasm bank at the University of California, Davis, the United States. The experiment was arranged in a randomized block design, with three replications and three plants per plot. Root mass, nematodes per gram of root and reproduction factor were determined and used as quantitative variables; 16 multi categoric descriptors were also evaluated. The traits were analyzed using the Ward-Modified Location Model procedure (Ward-MLM) for the composition of genotype groups. Genetic parameters and prediction of genetic values by Restricted Maximum Likelihood / Best Linear Unbiased Prediction (REML / BLUP) were assessed. The Ward-MLM classification strategy supported the formation of three homogeneous groups. Group I comprised 13 hybrids; Group II, 26 hybrids; and Group III, 18 hybrids. Groups II and III contained hybrids resistant to P. brachyurus. High broad sense heritability values were found for root mass, reproduction factor and nematodes per gram of root, which provided genetic gain and allowed selection of resistant genotypes available for cloning, since the total genetic variance occurred due to the dominance effects. Of the 57 genotypes assessed, those with the lowest genotypic values for reproduction factor were selected as resistant, including: CH3.2, CH3.23, CH3.8, CH3.37, CH3.38, CH3.41, CH3.36, CH2.1, CH2.7, CH1.1, CH1.3 and CH1.2.

Resistance to Pratylenchus brachyurus in Vitis species population through multivariate approaches and mixed models

Genetically diverse interspecific hybrids of Vitis were selected for resistance to Pratylenchus brachyurus. Three segregating populations with 57 hybrid crosses were evaluated. The parents included Vitis romanetiiC166-043 × 07355-075, 06354-047 × Cereza and 06354-047 × Nocera, selected from the germplasm bank at the University of California, Davis, the United States. The experiment was arranged in a randomized block design, with three replications and three plants per plot. Root mass, nematodes per gram of root and reproduction factor were determined and used as quantitative variables; 16 multi categoric descriptors were also evaluated. The traits were analyzed using the Ward-Modified Location Model procedure (Ward-MLM) for the composition of genotype groups. Genetic parameters and prediction of genetic values by Restricted Maximum Likelihood / Best Linear Unbiased Prediction (REML / BLUP) were assessed. The Ward-MLM classification strategy supported the formation of three homogeneous groups. Group I comprised 13 hybrids; Group II, 26 hybrids; and Group III, 18 hybrids. Groups II and III contained hybrids resistant to P. brachyurus. High broad sense heritability values were found for root mass, reproduction factor and nematodes per gram of root, which provided genetic gain and allowed selection of resistant genotypes available for cloning, since the total genetic variance occurred due to the dominance effects. Of the 57 genotypes assessed, those with the lowest genotypic values for reproduction factor were selected as resistant, including: CH3.2, CH3.23, CH3.8, CH3.37, CH3.38, CH3.41, CH3.36, CH2.1, CH2.7, CH1.1, CH1.3 and CH1.2.(AU)

Relationship among soil properties, root-lesion nematode population,and soybean growth / Relação entre atributos de solo, população de nematoide das lesões radiculares e crescimento de plantas de soja

Root-lesion nematode (RLN (Pratylenchus brachyurus) is an important challenge to soybean production in Central Brazil due to its widespread occurrence, along with the absence of resistant cultivars and strategies for its management. The aim of this research was to evaluate the relationship among soil properties, RLN populations, and soybean crop growth using geostatistical analysis. The experiment was conducted in a soybean field located in the northern half of Mato Grosso state, in Brazil, with a history of damages by RLN. The results suggest a positive correlation between plant height and values of pH, Ca, Mg, and base saturation. On the other hand, RLN population was positively correlated with organic carbon, cation exchange capacity, and soil potential acidity. Moreover, our findings also indicate that soybean plant growth is reduced under acidic soil conditions, as susceptibility to RLN increases. Thus, the correction of soil acidity to suitable levels for soybean crop becomes an important strategy to minimize damages by RLN.(AU)

O nematoide das lesões radiculares (NLR) (Pratylenchus brachyurus) representa um importante desafio para a produção de soja na região central do Brasil, devido a sua ocorrência generalizada e à ausência de cultivares resistentes e de estratégias adequadas para o seu manejo. O objetivo deste trabalho foi estudar as relações entre atributos de solo, a população de NLR e o crescimento de plantas de soja, usando ferramentas de geoestatística. O estudo foi realizado em área de produção comercial de soja na região do médio norte do Estado de Mato Grosso, com histórico de danos causados pelo NLR. Os resultados indicam que há correlação negativa entre a intensidade dos sintomas causados pela infestação do NLR e alguns atributos químicos do solo, tais como pH, Ca, Mg e saturação por bases. A população do NLR é positivamente correlacionada ao carbono orgânico, a capacidade de troca de cátions e a acidez potencial do solo. Há evidências de que a acidez do solo aumenta a suscetibilidade das plantas de soja ao ataque do NLR. Nesse sentido, a correção da acidez do solo para níveis adequados à cultura da soja é uma importante estratégia para minimizar os danos causados pelo NLR.(AU)

Relationship among soil properties, root-lesion nematode population,and soybean growth / Relação entre atributos de solo, população de nematoide das lesões radiculares e crescimento de plantas de soja

Root-lesion nematode (RLN (Pratylenchus brachyurus) is an important challenge to soybean production in Central Brazil due to its widespread occurrence, along with the absence of resistant cultivars and strategies for its management. The aim of this research was to evaluate the relationship among soil properties, RLN populations, and soybean crop growth using geostatistical analysis. The experiment was conducted in a soybean field located in the northern half of Mato Grosso state, in Brazil, with a history of damages by RLN. The results suggest a positive correlation between plant height and values of pH, Ca, Mg, and base saturation. On the other hand, RLN population was positively correlated with organic carbon, cation exchange capacity, and soil potential acidity. Moreover, our findings also indicate that soybean plant growth is reduced under acidic soil conditions, as susceptibility to RLN increases. Thus, the correction of soil acidity to suitable levels for soybean crop becomes an important strategy to minimize damages by RLN.

O nematoide das lesões radiculares (NLR) (Pratylenchus brachyurus) representa um importante desafio para a produção de soja na região central do Brasil, devido a sua ocorrência generalizada e à ausência de cultivares resistentes e de estratégias adequadas para o seu manejo. O objetivo deste trabalho foi estudar as relações entre atributos de solo, a população de NLR e o crescimento de plantas de soja, usando ferramentas de geoestatística. O estudo foi realizado em área de produção comercial de soja na região do médio norte do Estado de Mato Grosso, com histórico de danos causados pelo NLR. Os resultados indicam que há correlação negativa entre a intensidade dos sintomas causados pela infestação do NLR e alguns atributos químicos do solo, tais como pH, Ca, Mg e saturação por bases. A população do NLR é positivamente correlacionada ao carbono orgânico, a capacidade de troca de cátions e a acidez potencial do solo. Há evidências de que a acidez do solo aumenta a suscetibilidade das plantas de soja ao ataque do NLR. Nesse sentido, a correção da acidez do solo para níveis adequados à cultura da soja é uma importante estratégia para minimizar os danos causados pelo NLR.

Meloidogyne and Pratylenchus species in sugarcane fields in the state of Alagoas, Brazil

ABSTRACT: The objective of this study was to accomplish a survey on populations of Meloidogyne and Pratylenchus species in sugarcane farming areas in the state of Alagoas, Brazil. Twenty samples of soil and roots were processed to extract and quantify nematodes; however, the identification of Meloidogyne species was performed using only 12 samples. Pratylenchus spp. were reported at moderate population levels of 68-1556 specimens 50g-1 of roots and 2-298 specimens 100cm-3 of soil in twenty analyzed samples. For Meloidogyne spp., these values were of 12-487 specimens 50g-1 of roots and 0-140 specimens 100cm-3 of soil. Based on electrophoresis of esterase isozymes, M. incognita was reported to be the most frequent species, followed by M. javanica and M. arenaria. Pratylenchus species identified through morphometrical and morphological characteristics were P. zeae and P. brachyurus , with predominance for the first species. No significant correlation (P0.05) were reported between nematode populations and sugarcane cropping systems.

RESUMO: O objetivo deste trabalho foi realizar um levantamento de espécies de Meloidogyne e de Pratylenchus existentes em áreas de cultivo de cana-de-açúcar, no estado de Alagoas. Vinte amostras de solo e raízes foram processadas para a extração e quantificação, sendo a identificação das espécies de Meloidogyne realizada em 12 amostras. Detectou-se a presença de Pratylenchus spp. em níveis populacionais médios de 68-1556 espécimes 50g-1 de raízes e 2-298 100cm-3 de solo, em todas as amostras. Para Meloidogyne spp., esses valores foram de 12-487 50g-1 de raízes e 0-140 100cm-3 de solo. Com base na eletroforese da isoenzima esterase, M. incognita foi a espécie mais frequente, seguida por M. javanica e M. arenaria . As espécies de Pratylenchus identificadas pelas características morfológicas e morfométricas, foram P. zeae e P. brachyurus , com predomínio da primeira espécie. Não houve correlações significativas (P0,05) entre as populações de nematoides e as características dos sistemas de cultivo de cana-de-açúcar.

Meloidogyne and Pratylenchus species in sugarcane fields in the state of Alagoas, Brazil / Espécies de Meloidogyne e de Pratylenchus em áreas cultivadas com cana-de-açúcar no estado de Alagoas

he objective of this study was to accomplish a survey on populations of Meloidogyne and Pratylenchus species in sugarcane farming areas in the state of Alagoas, Brazil. Twenty samples of soil and roots were processed to extract and quantify nematodes; however, the identification of Meloidogyne species was performed using only 12 samples. Pratylenchus spp. were reported at moderate population levels of 68-1556 specimens 50g-1 of roots and 2-298 specimens 100cm-3 of soil in twenty analyzed samples. For Meloidogyne spp., these values were of 12-487 specimens 50g-1 of roots and 0-140 specimens 100cm-3 of soil. Based on electrophoresis of esterase isozymes, M. incognita was reported to be the most frequent species, followed by M. javanica and M. arenaria. Pratylenchus species identified through morphometrical and morphological characteristics were P. zeae and P. brachyurus , with predominance for the first species. No significant correlation (P≤0.05) were reported between nematode populations and sugarcane cropping systems.

O objetivo deste trabalho foi realizar um levantamento de espécies de Meloidogyne e de Pratylenchus existentes em áreas de cultivo de cana-de-açúcar, no estado de Alagoas. Vinte amostras de solo e raízes foram processadas para a extração e quantificação, sendo a identificação das espécies de Meloidogyne realizada em 12 amostras. Detectou-se a presença de Pratylenchus spp. em níveis populacionais médios de 68-1556 espécimes 50g-1 de raízes e 2-298 100cm-3 de solo, em todas as amostras. Para Meloidogyne spp., esses valores foram de 12-487 50g-1 de raízes e 0-140 100cm-3 de solo. Com base na eletroforese da isoenzima esterase, M. incognita foi a espécie mais frequente, seguida por M. javanica e M. arenaria . As espécies de Pratylenchus identificadas pelas características morfológicas e morfométricas, foram P. zeae e P. brachyurus , com predomínio da primeira espécie. Não houve correlações significativas (P≤0,05) entre as populações de nematoides e as características dos sistemas de cultivo de cana-de-açúcar.