Maria Imaculada Pontes Moreira Lima

Occurrence of head blast in barley

In the 2001 and 2002 crop seasons, barley (Hordeum vulgare L.) spikes showing symptoms similar to wheat (Triticum aestivum L.) and rice (Oryza sativa L.) blast were collected in commercial fields in the states of Rio Grande do Sul, Minas Gerais, and Goias, Brazil, as well as in experimental plots grown by the National Wheat Research Center (Embrapa Trigo) in the counties of Passo Fundo and Tapera, RS. The characteristic symptoms such as spike tip death (Figure 1A) and bright black spots of the rachis,were associated with pear-shaped, hyaline conidia, of up to three cells, 27.06-34.44 μm long and 9.84-12.3 μm wide, inherent characteristics of the fungus Pyricularia grisea (Cooke) Saccardo synonym P. oryzae Cavara [Tel.: Magnaporthe grisea (Hebert) Barr]. Attempting to confirm this etiology, an isolation was made on potato dextrose agar (PDA), with incubation at 22 ± 2 C and 12 h under light. Microorganism sporulation was obtained according to Anjos & Charchar (Fitopatologia Brasileira 25:205. 2000). Spikes of barley BR 2 were inoculated with a spore suspension (2.5 x 10 spores ml). Two inoculation procedures were used: sprinkling spore suspension and applying drop suspension on the rachis in two opposite spikelets. Plants were kept for 24 h in a humid chamber made from semitransparent, dark polyethylene bags, in the greenhouse. The spikes were sprayed with distilled water in the morning and in the afternoon for three consecutive days to keep them wet. Characteristic disease symptoms were recorded from the twelfth day onwards (Figure 1B). Inoculation by spraying resulted in the total death of most spikes. The microorganism isolated from inoculated spikes showed characteristics of P. grisea, confirming Koch′s postulates. Pyricularia grisea affecting barley spikes in Brazil is hereby reported for the first time. FIG. 1 Barley (Hordeum vulgare) spikes affected by Pyricularia grisea: A) Symptoms in spikes under natural conditions; B) Symptoms observed in cv. BR 2 after inoculation.

Relação entre a incidência de Fusarium graminearum em sementes, emergência e ocorrência de giberela em plântulas de trigo

Com o objetivo de verificar o comportamento de 30 genotipos de trigo em relacao a emergencia e a incidencia de giberela em plântulas provenientes de sementes portadoras de Fusarium graminearum, foram instalados experimentos de laboratorio e casa-de-vegetacao. Em laboratorio, as sementes utilizadas para os experimentos de emergencia e incidencia de giberela foram analisadas para sanidade pelo metodo do papel de filtro com congelamento. Em casa-de-vegetacao, as sementes foram distribuidas em caixas de plastico, contendo areia tratada com brometo de metila. O delineamento utilizado foi o de blocos casualizados, constituido de 30 tratamentos com quatro repeticoes de 50 sementes, perfazendo um total de 200 sementes/tratamento. As avaliacoes da emergencia de plântulas e da incidencia de giberela foram feitas aos sete, 14 e 21 dias apos a semeadura (DAS), contando-se o numero de plântulas emergidas e retirando-se as plântulas sintomaticas, as quais foram submetidas a câmara umida, por 24 horas, em laboratorio. Nao houve diferenca significativa da incidencia do patogeno na emergencia das plântulas. Nao foi constatada correlacao entre a incidencia de giberela nas plântulas e o nivel de resistencia dos genotipos, bem como entre incidencia de giberela nas plântulas e a incidencia do patogeno nas sementes.

Occurrence of rice blast in barley leaves in Rio Grande do Sul, Brazil

Occurrence of Rice Blast in Barley leaves in Rio Grande do Sul, Brazil Magnaporthe grisea is reported for the first time affecting barley leaves in the state of Rio Grande do Sul, in experimental plots and in farmers fields in Victor Graeff county and surroundings. A brusone, causada pelo fungo Magnaporthe grisea (T.T. Hebert) M.E. Barr (anamorfo Pyricularia grisea Sacc.), foi constatada pela primeira vez na cultura de cevada (Hordeum vulgare L.) no Brasil em 1998 (Anjos & Charchar, Fitopatol. Bras. 25:205. 2000), no Distrito Federal afetando folhas da planta, cujos sintomas foram descritos como lesoes elipticas com centro de cor cinza e margem de cor marrom. Em 2001 e 2002, registrou-se sua ocorrencia afetando espigas nos estados de Goias, Minas Gerais e tambem no Rio Grande do Sul (Lima & Minella, Fitopatol. Bras. 28:207. 2003), cujos sintomas foram caracterizados por morte da porcao superior da espiga no ponto de infeccao no raquis e lesao preta brilhante nesse. Em 2005, a brusone em espigas de cevada foi observada, novamente, no Rio Grande do Sul em ensaios e lavouras no municipio Victor Graeff e arredores. Observou-se nas folhas sintomas similares aos de brusone descritos em cevada (Figura 1A). Na Embrapa Trigo, no Laboratorio de Fitopatologia, apos incubacao das folhas com sintomas em câmara umida, constatou-se nas lesoes a presenca de conidios em formato semelhante a pera, hialinos, com ate tres celulas, caracteristicas inerentes a conidios de Pyricularia. Realizou-se isolamento do fungo em meio de cultura BDA conforme Anjos & Charchar (2000). Plantas de cevada, cultivar BR 2, de aproximadamente 30 dias foram pulverizadas com uma suspensao de conidios na concentracao de 1,0 X 105 esporos mL-1 e mantidas em câmara umida no escuro por 24 horas a temperatura de 28 oC. Os primeiros sintomas da doenca foram registrados 48 horas apos a inoculacao. As dimensoes dos conidios produzidos em câmara umida foram de 10 μm de largura e 30-40 μm de comprimento. O re-isolamento do microorganismo a partir das lesoes produzidas nas folhas inoculadas (Figura 1B) comprovou a ocorrencia de P. grisea afetando folhas de cevada no estado do Rio Grande do Sul. Recebido 13 Dezembro 2006 Aceito 16 Marco 2007 FB 6134 FIG. 1 Folhas de cevada (Hordeum vulgare) com sintomas causados por Pyricularia grisea A. Sintomas em folha em condicoes naturais; B. Sintomas observados na cv. BR 2 apos inoculacao. A B

Avaliação da resistência à giberela de genótipos de cereais de inverno

Evaluating scab resistance on genotypes of winter cereals Scab incited by Gibberella zeae is an important disease affecting wheat (Triticum aestivum) and other Triticea [barley (Hordeum vulgare), triticale (X Triticosecale), and rye (Secale cereale). In moist weather, the fungus infects the heads during flowering. Scab reduces yields and also can produce harmful mycotoxins. Control measures besides cultivar resistance are insufficient. A nursery was set up under field conditions in order to evaluate scab resistance among cultivars. The protocol used at Embrapa Trigo for screening scab resistant cultivars is described

Uma ferrugem, causada por Phakopsora tomentosae sp. nov., em oiti , em Manaus

A rust fungus (Phakopsora tomentosae nov. sp.) is reported here on seedlings and trees of Licania tomentosa in Manaus, AM, Brazil. The symptoms related to the uredinial phase were die-back, blight of young leaves, and necrotic lesions on mature and old leaves. The telial state was observed as brownish crusts near the border of the necrotic lesions on the abaxial surface of mature and old leaves

Androgenic response of wheat genotypes resistant to fusariosis

The objective of this work was to assess the androgenic response, via microspore culture, of wheat genotypes with different levels of resistance to Gibberella zeae. The number of androgenic embryos per spike, and of green and albino plants was counted for the BRS 179 (moderately resistant), Frontana and Sumai 3 (resistant), and BRS 194, Embrapa 27, and Fielder (susceptible) genotypes. The degree of interference by the Fielder, Pavon 76, and Sumai 3 ovary-donor genotypes, used for co-culture with the microspore cells, was also assessed regarding androgenic response. Induction efficiency ranged from 0.33 embryo per spike for Embrapa 27 to 109.8 embryos for Frontana. Sumai 3 presented the second best response, and Embrapa 27 behaved as highly recalcitrant. The co-culture of ovaries from the Fielder genotype stands out from the others and positively interferes in the embryo induction rate. No significant differences were observed for the regeneration frequency of green plants; however, for albino plants, BRS 194 produced the highest rate. Frontana and Sumai 3 present the highest androgenic response rates and can be used in breeding programs for the rapid development of cultivars resistant to Gibberella zeae.

Rust in Licania tomentosa caused by Phakopsora tomentosae sp. nov., in Manaus.

A rust fungus (Phakopsora tomentosae nov. sp.) is reported here on seedlings and trees of Licania tomentosa in Manaus, AM, Brazil. The symptoms related to the uredinial phase were die-back, blight of young leaves, and necrotic lesions on mature and old leaves. The telial state was observed as brownish crusts near the border of the necrotic lesions on the abaxial surface of mature and old leaves

Rust in Licania tomentosa caused by Phakopsora tomentosae in the state of Manaus, Amazonas, Brazil

A rust fungus (Phakopsora tomentosae nov. sp.) is reported here on seedlings and trees of Licania tomentosa in Manaus, AM, Brazil. The symptoms related to the uredinial phase were die-back, blight of young leaves, and necrotic lesions on mature and old leaves. The telial state was observed as brownish crusts near the border of the necrotic lesions on the abaxial surface of mature and old leaves