Hiroshi Kimati

Efeito da temperatura no crescimento micelial e patogenicidade de Pythium spp. que ocorrem em alface hidropônica

Doze isolados de Pythium foram obtidos de raizes de alface cultivada em sistemas hidroponicos comerciais, apresentando ou nao sintomas de apodrecimento. Tres desses isolados foram identificados como Pythium helicoides Drechsler (H1, H2 e H3), cinco como pertencentes ao grupo F (F1 a F5) e quatro ao grupo T (T1 a T4) de Pythium. A identificacao das especies foi realizada baseando-se nas caracteristicas morfologicas. O efeito da temperatura (10, 15, 18, 21, 24, 27, 30, 37 e 40oC) sobre o crescimento micelial foi determinado para todos os isolados. As temperaturas minima e maxima, estimadas pela funcao beta generalizada, variaram de 3,5 a 10oC e de 40 a 40,7oC, respectivamente. A temperatura otima foi de 24 a 37oC para P. helicoides, de 25 a 35oC para o isolado F4 e de 21 a 30oC para os demais isolados. A patogenicidade e a agressividade dos isolados foram avaliadas, inoculando-se sementes de alface cv. Veronica, semeadas em agar-agua, a 21 e 30oC. A 30oC, os isolados de P. helicoides foram notadamente os mais agressivos, ocasionando 100 % de mortalidade das sementes logo apos sua germinacao. A 21oC, todos os isolados induziram subdesenvolvimento de plântulas, acompanhado ou nao de necrose dos tecidos radiculares. Trata-se do primeiro relato de P. helicoides para o Brasil e a primeira referencia mundial da especie em hidroponia.

Glomevella cingulata (Stonem.) spauld. et v. schrenk. F. SP. phaseoli N.F., fase ascógena do agente causal da antracnose do feijoeiro

O presente trabalho versa sobre a obtencao da fase perfeita de Colletotriohum lindemuthianum (Sacc. et Magn.) Scrib., dirimindo duvidas quanto a sua existencia, suscitada pelo primeiro relato feito por SHEAR e WOOD (1913). Apos ter encontrado duas linhagens heterotalicas que formaram ascosporos em acasalamentos, os autores estudaram alguns fatores ambientais que favorecem a reproducao sexuada, chegando-se as seguintes conclusoes: peritecios se formaram sobre varios meios de cultura semi-sinteticos em cuja composicao entram glucose, Ca(N03)2.4H20(, MgSO4.7H2O e KH2PO4, agar e agua; a quantidade de glucose deve ser igual ou maior do que 4g/l, a de Ca(NO3)2.4H2O de 0,15 a 0,60 g/l e a relacao C/N deve estar entre 29,8 a 89,6:1; a adicao de vitaminas alterou levemente o nivel de aproveitamento de Ca(NO3)2.4H2O, nao havendo boa producao de peritecio ao nivel de 0,15 g/l mas permitindo-se ate o nivel de 1 g/l, mantendo-se as relacoes C/N mais ou menos no mesmo nivel; a luz, nos estagios final ou inicial ou em periodos alternados acima de 8 horas, inibiu a formacao de ascosporos, sendo, portanto, essencial a escuridao continua; peritecios se formaram sob condicoes de pH variavel de 4,0 a 6,0; peritecios ejetam ascosporos em condicoes de alta umidade; a temperatura em que foram obtidos os peritecios foi sempre de 209C. Do acasalamento de linhagens conidiais de C.lindemuthianum o autor obteve resultados a priori comparaveis aos de trabalhos geneticos feitos com G.cingulata, chegando-se a conclusao de que as linhagens usadas sao heterotalicas possivelmente condicionadas por varios fatores geneticos. Isolamentos ascosporicos foram inoculados, sendo todos patogenicos ao feijoeiro, pelo menos para a variedade Michelite. Comparando morfologicamente a fase ascogena de C.lindemuthvanwn com G.cvngulata, o autor propoe o nome de Glomerelia cingulata (Stonem.) Spauld et v. Schrenk f.phaseoli n.f.

Observações preliminares sobre a malformação em inflorescencias de mangueira (Mangifera indica L.) e fungo, alguns insetos e ácaro nelas encontrados

A malformacao de inflorescencias e o superbrotamento de gemas terminais e axilares de mangueiras dos Estados de Sao Paulo e Pernambuco sao relacionados com o acaro Aceria mangiferae Sayed, 1946 (Acarina, Eriophyidae) e o fungo Fusarium moniliforme subglutinans, sendo este ultimo considerado, empiricamente, como o principal agente causal da doenca. Varios insetos associados as inflorescencias de mangueiras foram coletados: lagarta de Eupithecia sp. (Tephroclystis), (Lepidoptera, Geometriidae, Hydriomeninae); Frankliniella cubensis Hood, 1925 (Thysanoptera, Thripidae); coleopteros pertencentes as familias Nitidulidae e Cryptophagidae.

Efeito da solarização do solo, seguida pela aplicação de Trichoderma spp. ou de fungicidas, sobre o controle de Pythium aphanidermatum e de Rhizoctonia solani AG-4

The development of alternative strategies for soil desinfestation with methyl bromide is necessary since the use of this compound faces increasing restrictions worldwide. Therefore the effect of soil solarization, followed by the application of isolates of Trichoderma spp. or fungicides, was evaluated for the control of Pythium aphanidermatum and Rhizoctonia solani, both can cause damping-off and root rots of several crops. Two experiments were carried out, one under greenhouse conditions and the other one under field conditions, both in a randomized block design, in factorial scheme (2x3), involving the combination of soil solarization (solarized and non-solarized soils) and the application of chemical or biological treatments, plus controls. Nylon bags containing soil naturally infested with P. aphanidermatum or soil with propagules of R. solani AG-4 were buried at 10 cm soil depth in plots solarized or non-solarized. After 30 days of solarization the bags were collected and the soil infested with P. aphanidermatum was treated with Trichoderma sp. (isolate IB-26) or with the fungicide metalaxyl + mancozeb, whereas the soil containing propagules of R. solani received an isolate of Trichoderma sp. (isolate IB-17) or the fungicide pencycuron. Fungicide suspensions were irrigated over the soil. A control was maintained for the soils infested with both pathogens. Viability of P. aphanidermatum and R. solani was evaluated by post-emergence damping-off of cucumber seedlings and by pre and post-emergence damping-off of radish seedling, respectively. Soil solarization, the biological treatment and the association of both treatments had no effect on the control of P. aphanidermatum, which was achieved only by the treatment with metalaxyl + mancozeb in the solarized and non-solarized soil. Soil solarization applied in both environments as well as the fungicide pencycuron were effective to control R. solani, but the association of both treatments did not have any synergistic effect. The treatment with the isolate of Trichoderma sp. IB-17 had no effect on R. solani, and was not favored by soil solarization.

Algumas raças fisiológicas de Colletotrichum lindemuthianum (Sacc. et Magn.) Scrib. que ocorrem no estado de São Paulo

This paper deals with the variation of Colletotrichum lindemuthianum (Sacc. et Magn.) Scrib., the fungus of bean anthracnose, one of the most serious diseases of bean in Brazil. Nineteen cultures of C. lindemuthianum were isolated from different regions of the State of Sao Paulo and were tested on the differential varieties Michelite, Dark Red Kidney and Perry Marrow, and on local varieties. The differential varieties were obtained from Cornell and Beltsville. The Hark Red Kidnety variety from Cornell behaved differently than that from Beltsville when inoculated with cultures C-12, C-13 and C-18. It was therefore impossible to say if these cultures belonged to race delta or to a new race not yet reported. For the culture C-3 and C-15 the Dark Red Kidney variety behaved similary, independent of its origin. Therefore these cultures belong to race alfa. For the other cultures the race is unknown. Local varieties were for the most part susceptible to all isolates tested. Some were variable in their reaction to isolates of the alfa race. Variety 54 was resistant to 18 isolates and variety 131 was resistant to all isolates in a single trial.

Isolamento, Caracterização Cultural-Morfológica, Patogenicidade e Serologia de Streptomyces spp. da Batata

Four methods of isolation of common superficial and deep scab were tested with the purpose of characterizing the isolates of Streptomyces scabies according to morphological and serological criteria and their pathogenicity. For isolation, obtained in water-agar at pH 10, a medium containing antibiotics, asparagine medium and coloidal quitin medium were tested. Water-agar pH 10 was the most efficient medium, giving rise to 129 colonies/Petri dishes, besides being of easy preparation, lower cost and giving better visualization of the colonies. The antibiotic medium gave an average of 54% of plated potato tuber fragments that yielded Streptomyces spp. growth. Asparagine and coloidal quitin showed averages of 36,3 and 2,5 colonies/Petri dish, respectively. For characterization of isolates, the yeast extract and malt medium were used, resulting in colony colors ranging from gray to brown and from white to cream, with and without production of pigment. The colonies formed flexuous or spiral spore chains, with variable size and producing or not aerial mycelium in spiral colonies. Nineteen isolates representing the different cultural and morphological types were inoculated in potato (Solanum tuberorum) cv. Monalisa through infestation of sterilized soil before the sowing of the seed tubers. Typical symptoms of the disease were reproduced 14 weeks after inoculation by eight isolates. Antisera produced in rabbits against three pathogenic isolates showed serological reaction (double diffusion in Ouchterlony gel-agar) for the homologous antigens and for few heterologous antigens. Streptomyces spp. isolates with confirmed pathogenicity did not show antigens in common.