Augusto César Pereira Goulart

Resistance spectra of wheat cultivars and virulence diversity of Magnaporthe grisea isolates in Brazil

Seventy-two monoconidial isolates of Magnaporthe grisea were obtained from the States of Mato Grosso do Sul and Parana. The isolates were inoculated on seedlings of 20 wheat (Triticum aestivum) cultivars under greenhouse conditions. The virulence diversity of M. grisea was assessed based on compatible and incompatible reactions of leaf blast on wheat cultivars. Fifty-four distinct virulence patterns were identified on test cultivars among the isolates collected from the two wheat growing States. Sixteen of these isolates corresponding to 22.2% showed similar virulence pattern. None of the wheat cultivars was resistant to all isolates of M. grisea, but the cultivars differed in degree of resistance as measured by the relative spectrum of resistance (RSR) and disease index (DI). Among the cultivars the RSR ranged from 0 to 53.3% and DI from 0.4662 to 0.9662 (0 to 1 scale). The wheat cultivar BR18 exhibited a broad resistance spectrum in relation to the rest of the tested cultivars to the isolates of M. grisea, and can be used in wheat resistance breeding.

Danos em trigo causados pela infecção de Pyricularia grisea

This work was carried out in order to quantify the damages in wheat yield due to natural infection by Pyricularia grisea, (causal agent of wheat blast), in different wheat cultivars and breeding lines, during 2004 crop season, at Dourados county, Mato Grosso do Sul State in the absence of other diseases. The experiments were developed under natural conditions and without fungicide spraying, in experimental plots located at Embrapa Agropecuaria Oeste and Indapolis. After heading stage, all spikes that showed the characteristic blast symptoms (black point infection in the rachis), had been identified and marked in an area of the 1m 2 . The blast and healthy spikes were harvested, counted and threshed separately. The damages were calculated based on the difference between the actual yield and the estimated yield potential. The results showed that the damages and

Efeito do tratamento de sementes de algodão com fungicidas no controle do tombamento de plântulas causado por Rhizoctonia solani

Effect of cotton seed dressing with fungicides for the control of seedling damping-off caused by Rhizoctonia solani This work was carried out at Embrapa Agropecuaria Oeste, Dourados, MS in order to evaluate the efficiency of several fungicides, applied as seed dressing, in the control of damping-off caused by Rhizoctonia solani. Greenhouse testing was performed, using the cotton (Gossypium hirsutum) cv. DeltaOpal. Treated and untreated seeds with the fungicides were sowed in sand contained in plastic flats, placed in individual and equidistant wells, 3 cm deep. Inoculation with R. solani was done by the homogeneous distribution of the fungus inoculum onto the substrate. The fungus was grown for 35 days on autoclaved oat seeds and then ground to Foram utilizados 9 g de inoculo por bandeja de areia. Foi observado efeito do tratamento fungicida na emergencia inicial e final de plântulas, com destaque para triadimenol + pencycuron + tolylfluanid e triadimenol + tolylfluanid, seguidos de carboxin + thiram, triadimenol e carboxin + thiram + carbendazim. Os tratamentos mais eficientes no controle do tombamento de posemergencia do algodoeiro foi obtido com a mistura triadimenol + pencycuron + tolylfluanid, seguida de triadimenol, triadimenol + tolylfluanid e carboxin+thira m. Nenhum dos fungicidas testados foi fitotoxico ao algodao. Palavras-chave adicionais: Gossypium hirsutum, emergencia, tratamento quimico, damping-off.

Cottonseeds treatment with fungicides for the control of seedling damping-off pathogens

The cotton seedling damping-off is a worldwide problem caused by a complex of soil-borne and seed-borne fungi, occurring separately or in combination, and cause pre- or post-emergence damping-off. The main etiological agents causing the damping-off are Rhizoctonia solani Khun, Colletotrichum gossypii South and Colletotrichum gossypii var. cephalosporioides. The aim of this work was to evaluate the effectiveness of many fungicides that have been used on the treatment of cottonseeds to control pathogens associated with seeds and/or presents in the soil. Cottonseeds free of pathogens, inoculated and non-inoculated with Colletotrichum gossypii var. cephalosporioides (Cgc), were treated with tolylfluanid + pencycuron + triadimenol; carboxin + thiram and fluazinam + thiophanate methyl. On the Growing on Test, the non-treated seeds inoculated with Cgc showed a lower level of emergence. The higher level of emergence occurred on non-inoculated seeds treated with tolylfluanid + pencycuron + triadimenol. The most efficient treatment in the control of post-emergence damping-off in substrates containing Rhizoctonia solani, was obtained with the mixture of tolylfluanid + pencycuron + triadimenol, followed by carboxin + thiram. In the field, the higher severity of ramulosis, caused by Cgc, occurred in plants from non-treated seeds inocculated with Cgc. None of the fungicides tested showed phytotoxity to cotton.

Efeito do tratamento de sementes de algodoeiro com fungicidas no controle do tombamento em relação à densidade de inóculo de Rhizoctonia solani.

The fungus Rhizoctonia solani Kuhn is considered the most important cause of cotton damping-off in Brazil. Treatment of seeds with fungicides is the most efficient and economical procedure to control this disease. The performance of fungicides depends, among many other factors, of the pathogen population in the soil. This work was carried out, under greenhouse conditions at Embrapa Agropecuaria Oeste, Dourados, MS, with the goal to determine the effect of treatment of cotton seeds with fungicides to control damping-off at different inoculum densities of R. solani in the soil. Seeds of cultivar DeltaOpal treated or not with different fungicides were sowed 3 cm deep in sand contained in plastic flats. Seeds were placed in individual and equidistant wells. Inoculum of the fungus was homogeneously distributed in the substrate. The fungus was grown for 35 days on autoclaved oat seeds and then ground to powder using a mill until reach the size of 1mm. Four inoculum densities were tested: 1 g; 2 g; 3 g e 4 g/plastic flat with dimensions of 56x35x10 cm. The effect of the fungicide treatment on initial and final seedling emergence, as well as, in the control of post and pre-emergence damping-off was observed. Treatment of seed with a combinations of fungicides gave the best results in controlling damping-off as compared to the use of each fungicide alone. The interaction fungicides x inoculum densities, was significant indicating that the efficiency of the fungicides was somehow affected by the fungus densities. Fungicides had the best performance at low inoculum densities (1g and 2g/flat). As for fungi populations of 3g and 4g/flat, the efficiency of all fungicides tested decreased sharply, with a reduced control of the disease. The fungicides used in this study did not have any phytotoxic effect on cotton seedlings.

Detection of Pyricularia grisea on barley seeds produced under central pivot irrigation in the Brazilian Cerrado.

ABSTRACT Detection of Pyricularia grisea on barley seeds produced undercentral pivot irrigation in the Brazilian Cerrado Occurrence of Pyricularia grisea on barley ( Hordeumvulgare ) seeds produced under central pivot irrigation is reportedfor the first time in the Brazilian Cerrado, DF, Bra zil. As sementes de cevada ( Hordeum vulgare L.) assumemum importante papel na disseminacao de inumeros patogenoscausadores de doencas, visto que, do ponto de vista de sanidade,alem de sofrerem ataque de inumeros agentes fitopatogenicos,as sementes podem servir de fonte de inoculo para cultivosposteriores, como tambem se constituir em veiculo para intro-ducao de patogenos em areas livres de determinadas doencas.Dentre os patogenos associados as sementes de cevada, osfungos constituem o mais importante e numeroso grupo,merecendo destaque Bipolaris sorokiniana (Sacc.) Shoem., Drechslera teres (Sacc.) Shoem. e Fusarium graminearum Schwabe, agentes causais de importantes doencas deste cerealno Brasil (Barba

Espaçamento entre linhas e severidade da ferrugem-asiática da soja

ABSTRACT A ferrugem-asiatica da soja, causada pelo fungo Phakopsorapachyrhizi Syd. & P.Syd., tem sido, desde sua deteccao no Brasil (25),um dos principais desafios fitopatologicos para essa cultura. Ate omomento, a unica forma de controle da doenca, apos sua instalacao nalavoura, e por meio da aplicacao de fungicidas, o que onera os custosda lavoura. Alem disso, o seu uso continuo, como unica estrategia demanejo, pode causar a selecao de patogenos resistentes ou menossensiveis aos fungicidas utilizados e, por conseguinte, a ineficienciado controle da doenca, com a aplicacao exacerbada de fungicidas eelevacao dos custos de producao.Dessa forma, e necessaria a combinacao de outras praticas agricolaspara o controle mais efetivo das doencas, a fim de garantir a eficienciaeconomica e ambiental da agricultura. Neste contexto, a adocao domanejo integrado torna-se uma estrategia adequada para atender aoproposito de eficiencia e sustentabilidade no controle de doencas. Noentanto, pouco avanco se obteve no conhecimento sobre o manejocultural da ferrugem-asiatica da soja, principalmente com relacao aoarranjo de plantas.O efeito do arranjo de plantas e do espacamento entre linhas desemeadura tem sido estudado por diversos pesquisadores para asmais variadas culturas (3, 4, 5, 8, 11, 12, 13, 14, 15, 16, 17, 22). Nacultura da soja, o espacamento entre linhas interfere na populacao ecrescimento de plantas daninhas (3), no indice de area foliar, navelocidade de fechamento das entrelinhas (13) e no rendimento degraos (12, 14). No entanto, pouco se tem estudado sobre o efeito deespacamento entre linhas na severidade de doencas, principalmente daferrugem-asiatica da soja, exceto pelos trabalhos realizados porMadalosso et al. (15) e Soares & Lonien (22).Sabe-se que o desenvolvimento de uma doenca depende dainteracao entre planta, agente patogenico e fatores ambientais (1, 2, 7,20). Portanto o ambiente, representado tanto pelas condicoesmeteorologicas como pelo micro clima, e um fator relevante nesta

Ocorrência de mela causada por Rhizoctonia solani AG4-HGI em plântulas de algodoeiro no Brasil

UNESP - Universidade Estadual Paulista, Campus de Ilha Solteira, Departamentode Fitossanidade, Engenharia Rural e Solos, 15385-000 Ilha Solteira, SPAutor para correspondencia: Augusto Cesar Pereira Goulart. (goulart@cpao.embrapa.br)Data de chegada: 19/11/2009. Aceito para publicacao em: 25/01/2011. 1696O tombamento de plântulas de algodoeiro, causado por

Controle integrado da ferrugem asiática da soja (Phakopsora pachyrhizi) com o fungicida fluquinconazole aplicado nas sementes em associação com outros fungicidas pulverizados na parte aérea da cultura

O objetivo deste trabalho foi avaliar o controle da ferrugem asiatica da soja (Phakopsora pachyrhizi) pela integracao do tratamento de sementes com o fungicida fluquinconazole e a pulverizacao de fungicidas na parte aerea da cultura. Dois ensaios foram instalados na safra 2006/07, um em Dourados, MS, usando sementes de soja da cv. BRS 245 RR e o outro em Paulinia, SP com a cv. CD 208. Foram avaliados a severidade da doenca, a desfolha e o rendimento de graos. O delineamento experimental usado foi o de blocos ao acaso, com quatro repeticoes, em arranjo fatorial 2x5, com dois tratamentos de semente, com e sem fluquinconazole, e cinco combinacoes de misturas de fungicidas aplicadas na parte aerea da soja. Os resultados observados nestes ensaios mostraram que a adicao do fluquinconazole ao tratamento de sementes padrao na cultura da soja, sem considerar a aplicacao de fungicidas na parte aerea da cultura, atrasou a evolucao da ferrugem da soja, apresentando diferenca significativa com o tratamento de sementes padrao sem o fluquinconazole, em relacao a severidade e desfolha, o que nao ocorreu com relacao ao rendimento de graos. Considerando a integracao entre o tratamento de sementes com fluquinconazole e os fungicidas aplicados na parte aerea da soja, na maioria das avaliacoes de severidade da ferrugem e de desfolha, bem como em relacao ao rendimento de graos da cultura, nao foi observada interacao significativa entre estas duas praticas. As aplicacoes foliares de fungicidas foram eficientes para o controle da ferrugem da soja, proporcionando menores niveis de severidade e de desfolha, o que refletiu de forma positiva no rendimento de graos da cultura, em comparacao com a testemunha nao tratada. Nao foram observados efeitos fitotoxicos nas plantas de soja decorrentes da utilizacao do fungicida fluquinconazole nas sementes.

Suscetibilidade de cultivares de algodoeiro a Rhizoctonia solani e benefícios do tratamento de sementes com fungicidas

The objective of this work was to evaluate the behavior of six cotton cultivars (BRS-Ipe, BRS-Aroeira, BRS-Cedro, Fibermax 966, DeltaOpal and CNPA Ita 90-II) in relation to Rhizoctonia solani AG-4 and the benefits of cotton seed treatment with fungicides, for each tested cultivar, for the control of damping-off in relation to inoculum densities of this fungus. This experiment was carried out at greenhouse conditions at Embrapa Agropecuaria Oeste, in Dourados, MS. Four inoculum densities were tested (0; 1; 2 and 3g of fungus inoculum/plastic tray with dimensions of 56x35x10cm) in the trial. The evaluations were done based on symptoms development and seedling survival, using initial and final emergence and pre and pos damping-off data. Treated and untreated seeds with fungicides mixture tolylfluanid + pencycuron + triadimenol (30+50+50g a.i./100kg of seeds) were sowed in sand contained in plastic trays, by placing in equidistant 3-cm-deep wells. The inoculation with R. solani AG-4 was done by the homogeneous distribution of the fungus inoculum onto the substrate. The fungus was grown for 35 days on autoclaved oat seeds and then ground to powder using a mill (1mm). Significant effect of the interactions cultivars x inoculum densities, cultivars x fungicides and inoculum densities x fungicides were oberved. The cultivars behavior was significantly influenced by different populations of R. solani. Results showed that the higher the inoculum density, the higher the disease level and the lower the emergence rates. It was also demonstrated the importance of cotton seed treatment with fungicides, with best results in relation to emergence and disease level (damping-off and lesioned seedlings), regardless of tested cultivar, being obtained when the seeds were treated with tolylfluanid + pencycuron + triadimenol. It was still observed that pathogen population significantly influenced the benefits of seed treatment, since the performance of fungicides was better when inoculum densities were low. In the absence of seed treatment with fungicides, differences among the cultivars in relation to R. solani were observed, being distinct in CNPA ITA 90 II and BRS Aroeira, followed by BRS Cedro and BRS Ipe, which showed higher tolerance to R. solani.