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The objective of this study was to evaluate the resistance reaction of Avena spp. after inoculation of different concentrations of eggs and juveniles of M. javanica and M. incognita. Ten oat genotypes (Avena sativa: UPFPS Farroupilha, UPFA Ouro, IPR Afrodite, AF1345 Ucraniana; A. strigosa: Agro Quaraí, Agro Esteio, Embrapa 139, Iapar 61 Ibiporã, UPFA 21 Moreninha, AF 12202) were evaluated in bioassays for resistance against the root-knot nematodes, Meloidogyne javanica and M. incognita. Susceptible (Solanum lycopersicum and Glycine max) and resistant (Crotalaria spectabilis) species were used as control treatments. Depending on the inoculum level, the oats showed a different response to nematodes. All genotypes of oats were resistant to M. javanica when a high inoculum level (5,000 eggs and J2 per plant) was used but under low inoculum level (1,500 eggs and J2 per plant), AF 12202, Iapar 61 Ibiporã, Agro Esteio and Agro Quaraí were susceptible. All genotypes of oats were resistant to the inoculation of 2,900 eggs and J2 of M. incognita, except for ‘Iapar 61’ that showed susceptibility in this concentration. At lower inoculum level (1,500 eggs and J2) Agro Quaraí, Agro Esteio and Iapar 61 Ibiporã were susceptible. The reaction of oats to M. javanica and M. incognita depends on the inoculum level. The resistance reaction at low inoculum density of A. sativa ‘AF 1345 Ucraniana’ and ‘IPR Afrodite’ allows its use in breeding programs in oats and suggests the possibility of management tool in areas infested with both root-knot nematode species.

The objective of this study was to determine and quantify the main phytonematodes found in soybean crops in the state of Rio Grande do Sul and to estimate the population level where they are found. Therefore, samples of soil and soybean roots were received from 154 municipalities of the Middle Plateau region of Rio Grande do Sul, from 2014 to 2016. After receiving and registering the samples, nematodes were extracted, identified and quantified in each sample. Through these data, it was determined the absolute frequency (AF), relative frequency (RF), absolute density (AD) and relative density (DR) of each nematode genus as well as their average population level in the municipalities. The main genera found in the study were Meloidogyne (found in 7.5% of the samples), Pratylenchus (6.2%), Heterodera (4.3%), Rotylenchulus (1.6%) and Helicotylenchus (22.9%). The species Meloidogyne species was not identified, but for Pratylenchus two species were identified, P. brachyurus and P. zeae. Besides these two genera, others were found, among them Heterodera glycines, Rotylenchulus reniformis and Helicotylenchus dihystera. The most frequently found nematode was H. dihystera, and in relation to population level, Meloidogyne spp. stands out for showing the highest levels in the municipalities in the three years of evaluation.

Made available in DSpace on 2021-07-14T10:19:22Z (GMT). No. of bitstreams: 0 Previous issue date: 2019-08-12. Added 1 bitstream(s) on 2021-07-14T11:27:09Z : No. of bitstreams: 1 S0034-737X2019000300220.pdf: 83319 bytes, checksum: 2123abc1118ddefa6834d77163ae6a19 (MD5) Nematodes of the genus Meloidogyne are associated with soybean cultivation, unknown the reaction of cultivars. The objective of this work was to determine the reaction of soybean cultivars to M. javanica and M. incognita. Twenty-seven soybean cultivars were sown in plastic pots, in a completely randomized experimental design with eight replicates. Ten days after emergence of the seedlings, in a separate experiment, M. javanica and M. incognita were inoculated. For M. javanica, cultivars classified as susceptible were BMX Lança IPRO, AMS Tibagi RR, BMX Vanguarda IPRO, NS 6700 IPRO, BMX Ativa RR, FPS Solimões RR, TEC 6702 IPRO, NS 5909 RR, NS 5445 IPRO, 54i52 RSF IPRO, M 6410 IPRO and NS 5959 IPRO and BMX Elite IPRO, NA 6211 RR, BMX Valente RR, FPS Júpter RR, FPS Iguaçú RR, BMX Tornado RR, GMX Cancheiro RR, TMG 7161 IPRO, TMG 7062 IPRO, FPS Solar RR, M 5730 IPRO, DM5958 RSF IPRO, NS 6006 IPRO, SYN 1163 RR and M 5947 IPRO were resistant. Regarding M. incognita, the resistant cultivars were FPS Iguaçú RR, FPS Solar IPRO, SYN 1163 RR and TMG 7062 IPRO. The cutlivars FPS Júpter RR, SYN 1163 RR e TMG 7062 IPRO were resistant to both nematodes. Universidade de Passo Fundo Breeder at OR Sementes Universidade de Cruz Alta Universidade Estadual Paulista “Julio de Mesquita Filho” Universidade Estadual Paulista “Julio de Mesquita Filho”

Asian soybean rust is one of the most destructive diseases that can be found in this crop. It can be largely controlled by fungicide application. The objective was to assess the sensitivity of P. pachyrhizi isolates to fungicides. The tests were performed in a completely randomized design, with six replicates. The sensitivity of twelve isolates to site-specific and multisite fungicides at concentrations of 0.1; 1.0; 10.0, and 100.0 mg L-1, plus a control with absence of fungicide (0.0 mg L-1) was assessed. Soybean leaflets were immersed in the appropriate fungicide solutions, disposed in wet chambers in plastic boxes, and inoculated using each uredinia suspension of P. pachyhrizi (5.0 x 104 uredospores mL-1), separately. Boxes were incubated for 20 days at a temperature of 23°C and a 12-hour photoperiod. Next, the number of uredinia per cm2 on the abaxial face of each leaflet was evaluated. The active ingredients prothioconazole, trifloxystrobin, fluxapiroxade, trifloxystrobin + prothioconazole, trifloxystrobin + bixafen + prothioconazole, azoxystrobin + benzovindiflupyr, and azoxystrobin + benzovindiflupyr + diphenoconazole were highly fungitoxic for the majority of the isolates, with EC50 lower than 1.0 mg L-1. Diphenoconazole, azoxystrobin, and fenpropimorph were considered moderately fungitoxic for nine of the twelve isolates, with EC50 between 1 and 10 mg L-1. The multisites mancozeb and copper oxychloride presented EC50 responses classified as low toxic for the twelve isolates and eight for chlorothalonil (EC50 between 10 mg L-1 and 50 mg L-1). Site-specific fungicides showed high-to-moderate fungitoxicity to P. pachyrhizi isolates, even as the multisites presented moderate-to-less toxic activity.

The objective of this study was to develop a methodology for inoculum production and inoculation of Passalora sojina in soybean to assess the reaction to frogeye leaf spot. Thus, sporulation of fungal races was quantified in five substrates under two light regimes. The temperature and the leaf wetness period that resulted in greater infection efficiency were also determined. Petri dishes containing the culture media Oat Flour Agar (OFA), Tomato Juice (FTJ), V8 agar juice (V8), Infant Food (IF) and Potato Sucrose Agar (PSA) plus isolates of P. sojina races 23, 24 and 25 were subjected to 12-h photoperiod and 24-h continuous dark. Inoculated plants were incubated at temperatures of 15, 20, 25, 30 and 35 ºC and leaf wetness periods of 12, 24, 36, 48 and 72 hours. Experimental design was completely randomized with five replicates. There was interaction among isolate, culture medium and photoperiod. The highest sporulation (conidia/cm2) was obtained in the culture media FTJ (race 23) and V8 (races 24 and 25) under 12-h photoperiod. The optimum temperature for the disease development was 27oC under 72 hours of continuous leaf wetness. RESUMO O objetivo desse trabalho foi desenvolver uma metodologia para produção de inóculo e inoculação de Passalora sojina em soja visando avaliar a reação à mancha foliar “olho-de-rã”. Para isso foi quantificada a esporulação de raças do fungo em cinco substratos, sob dois regimes luminosos. Também foi determinada a temperatura e duração do período de molhamento foliar que resultasse na maior eficiência da infecção. Placas de Petri com os meios de cultura Farinha de Aveia Ágar (FAA), Suco de Tomate Temperado (STT), Suco V8 ágar (V8), Alimento Infantil (AI) e Batata Sacarose Ágar (BSA) contendo isolados das raças de P. sojina 23, 24 e 25 foram submetidas aos fotoperíodos de 12 h e 24 h de escuro contínuo. Plantas inoculadas foram incubadas a temperaturas de 15, 20, 25, 30 e 35 ºC e períodos de molhamento foliar de 12, 24, 36, 48 e 72 h. O delineamento experimental foi inteiramente casualizado com cinco repetições. Houve interação entre isolado, meio de cultura e fotoperíodo. A maior esporulação (conídio/cm2) foi obtida no meio de cultura STT (raça 23) e no meio V8 (raças 24 e 25), sob fotoperíodo de 12 h. A temperatura ótima para o desenvolvimento da doença foi de 27 oC com 72 horas de molhamento foliar contínuo.

Sementes de trigo infectadas com Pyrenophora tritici-repentis, agente causal da mancha-amarela da folha, respondem em parte pelas epidemias causadas por este patogeno. A obtencao rapida de lotes de sementes com alta incidencia de P. tritici-repentis e fundamental para estudos de transmissao e controle. Sendo assim, o objetivo deste trabalho foi verificar se alteracoes no potencial hidrico do meio de cultura e variacoes na duracao da inoculacao podem favorecer a infeccao de sementes de trigo por P. tritici-repentis, sem comprometer a viabilidade destas sementes. Colonias do patogeno foram cultivadas sobre meio de cultura batata-dextrose-agar (BDA) basico, no potencial hidrico de -0,36 MPa, e no meio BDA com restricao hidrica, causada pela adicao de manitol, nos potenciais hidricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa. Foram realizadas analises para determinar o indice de crescimento micelial do fungo e o tempo de exposicao das sementes ao meio de cultura para o inicio do processo germinativo em funcao dos potenciais hidricos. Posteriormente, sementes de trigo foram colocadas em contato com as colonias de P. tritici-repentis durante 24, 48 e 72 horas nos potenciais hidricos de -0,4, -0,6, -0,8, -1,0 e -1,2 MPa, em esquema fatorial (potenciais hidricos x duracao da inoculacao) e delineamento inteiramente casualizado. Foram avaliadas as taxas de germinacao, de emergencia de plântulas em solo e de infeccao de sementes. Houve estimulo ao crescimento micelial nos menores potenciais hidricos, sendo que nesses potenciais, o tempo para inicio de germinacao e maior. A duracao da inoculacao de 24 horas e o uso de restricao hidrica com potencial de -0,4 MPa foram eficientes para infectar sementes de trigo com P. tritici-repentis, sem prejudicar a germinacao e a emergencia de plântulas em condicoes de laboratorio.

In a survey of damages caused by soybean root rot to crops in the south of Brazil for several years, a root rot caused by Phomopsis sp has been found with increasing frequency. The primary symptoms are seen when the main root is cut longitudinally, including the death of the wood which shows white coloration and well-defined black lines that do not have a defined format. Thus, based on similarity, it has been called geographic root rot due to its aspect resembling irregular lines that separate regions on a map. In isolations, colonies and alpha spores of Phomopsis have prevailed. Pathogenicity test was done by means of inoculation in the crown of plants cultivated in a growth chamber. The geographic symptoms were reproduced in plants and the fungus Phomopsis sp. was reisolated. In soybean stems naturally infected with pod and stem blight, geographic symptoms caused by Phomopsis phaseoli are found. To the known symptoms on stems, pods and grains, that of root rot caused by P. phaseoli is now added. Em levantamento de danos causados por podridões radiculares da soja, em lavouras do sul do Brasil durante vários anos, tem sido encontrado com maior frequência uma podridão radicular causada por Phomopsis sp. Os sintomas primários são visualizados quando se corta longitudinalmente a raiz principal, observando-se a morte do lenho ostentando coloração branca, com linhas negras bem definidas, sem um formato definido. Por isso, por semelhança, tem sido chamada de podridão radicular de geográfico, pelo aspecto que lembra as linhas irregulares separando regiões num mapa. Isolamentos foram feitos durante várias safras e feita a prova de patogenicidade. Nos isolamentos tem predominado colônias e os esporos alfa de Phomopsis sp. A prova de patogenicidade foi feita pela inoculação no colo de plantas cultivadas em câmara de crescimento. Reproduziram-se os sintomas de geográfico nas plantas e foi reisolado o fungo Phomopsis sp. Em hastes de soja naturalmente infectadas pela seca-da-haste e da-vagem são encontrados sintomas de geográfico causados por Phomopsis phaseoli. Aos sintomas conhecidos em hastes, vagens e grãos acrescenta-se agora o de podridão radicular causada por P. phaseoli.

Em experimentos conduzidos no campo, no sistema plantio direto, nas safras de verão de 2003/04, 2004/05 e 2005/06 foram avaliados os efeitos de culturas de inverno, da rotação e da monocultura sobre a emergência de plântulas, na incidência de podridões radiciais e no rendimento de grãos da soja. Demonstrou-se não haver efeitos das culturas de inverno sobre a emergência de plântulas da soja. Quanto à incidência de podridões radiciais em monocultura foi registrada uma intensidade de até 99,2%. O maior rendimento de grãos foi obtido na soja cultivada em rotação com uma safra com milho. Os fungos isolados do sistema radicial de plantas infectadas foram, Macrophomina phaseolina, Phomopsis sp., Fusarium spp. e Colletotrichum truncata. O solo da área experimental pode ser considerado supressivo aos fatores que reduzem a germinação, a emergência de plântulas e de morte de plântulas/plantas de soja. Quanto ao seu efeito em reduzir as podridões radiciais, ainda não se detectou efeito supressivo, porém a rotação da soja com o milho reduziu a incidência de podridões radiciais e aumentou o rendimento de grãos da soja. In experiments carried out in the field, under no-till planting system, in 2003/04, 2004/05 and 2005/06 summer growing seasons, the effects of winter crops, rotation and monoculture on seedling emergence, root rot incidence and soybean grain yield were assessed. There were no effects of winter crops on soybean seedling emergence. As to root rot incidence on monoculture, an intensity of up to 99.2% was recorded. Grain yield was highest when soybean was cultivated in one season of rotation with corn. The fungi isolated from the root system of infected plants were Macrophomina phaseolina, Phomopsis sp., Fusarium spp. and Colletotrichum truncata. The soil at the experimental area can be considered suppressive to factors that reduce soybean germination, seedling emergence, and seedling/plant death. Considering its effect in reducing root rot, a suppressive action has not been detected yet; however, soybean rotation with corn reduced root rot incidence and increased soybean grain yield.

The frogeye leaf spot, a disease caused by the fungus Cercospora sojina, affects soybean crops worldwide with enormous economic impact. In this study, we evaluated the combined effects of temperature and duration of leaf wetness periods on the intensity of frogeye leaf spot in soybean. Experiments were conducted in a growth chamber with cultivar Don Mario 7.0i at temperatures of 15, 20, 25, 30 and 35°C and leaf wetness periods of 12, 24, 36, 48 and 72 hours. The experimental design was completely randomized with five replications. When soybean plants were grown at 15°C, affected leaflet area, number of lesions per leaflet and diameter of lesions could only be measured after 60 hours of leaf wetness. At the temperatures of 20 and 25°C this period was reduced to 24 hours of leaf wetness, at 30oC, we found the need for 36 hours of leaf wetness and at a temperature of 35°C, 48 hours. The optimal temperatures for disease development were 27°C for diameter and affected leaflet area and 28°C for number of lesions per leaflet with 72 hours of leaf wetness. A cultura da soja apresenta grande importância mundialmente, entre as doenças que ocorrem nesta cultura está à mancha olho-de-rã (causada por Cercospora sojina). O objetivo deste trabalho foi avaliar a interação entre temperaturas e diferentes períodos de molhamento foliar na intensidade da mancha olho-de-rã em soja. O experimento foi conduzido em câmara de crescimento com a cultivar Don Mario 7.0i nas temperaturas de 15, 20, 25, 30 e 35ºC e os períodos de molhamento foliar de 12, 24, 36, 48 e 72 horas. Cinco experimentos foram realizados, um para cada temperatura, l5, 20, 25, 30 e 35ºC e os períodos de molhamento foliar 12, 24, 36, 48, 60 e 72 horas consistiram os tratamentos, o delineamento experimental foi inteiramente casualizado com cinco repetições. Quando as plantas foram submetidas à temperatura de 15oC, severidade foliar, número de lesões por folíolo e diâmetro da lesão foram observados somente com 60 horas de molhamento foliar, para temperaturas de 20 e 25oC com 24 horas de molhamento foliar, para temperatura de 30oC com 36 horas de molhamento foliar e para temperatura de 35oC com 48 horas de molhamento foliar. A temperatura ótima estimada para o desenvolvimento da doença foi de 27oC para severidade e diâmetro de lesões e de 28oC para número de lesões por folíolo, com 72 horas de molhamento foliar.