Gustavo Rubens de Castro Torres

Meloidogyne mayaguensis on Psidium guajava in Rio Grande do Norte

ABSTRACT Meloidogyne mayaguensis on Psidium guajava in Rio Grande doNorte This paper reports the occurrence of Meloidogynemayaguensis on Psidium guajava cv. Paluma in the State of RioGrande do Norte, Brazil. O Laboratorio de Agricultura Irrigada da Escola Superiorde Agricultura de Mossoro – ESAM, Rio Grande do Norte,recebeu, em junho de 2003, amostras de solo de rizosfera degoiabeira ( Psidium guajava L.) cv. Paluma e sistemas radicularesdeficientes constituidos por poucas raizes, finas e necrosadas,coletadas em pomar com aproximadamente 500 plantas, comsete anos de idade, situado no municipio de Touros–RN.Segundo o proprietario, as plantas doentes expressavamsintomas de amarelecimento e declinio, e distribuiam-se emreboleiras.Para diagnostico, amostras foram encaminhadas aoLaboratorio de Fitonematologia da Universidade Federal Ruralde Pernambuco; das quais aliquotas de solo de 300 cm 3 foramdestinadas ao processamento por flotacao centrifuga, segundoJenkins (1964) (Plant Disease Reporter, v.48, p.692, 1964), e 10g de raizes para trituracao em liquidificador, por 20 s, associadaa flotacao centrifuga. Nas amostras de solo e de raiz foramdetectadas 440 e 11.380 formas juvenis do segundo estadio,respectivamente, de

Severidade da podridão-verde em inhames e especialização fisiológica em Penicillium sclerotigenum

ABSTRACTSeverity of green rot in yellow and water yams and the physiological specialization of Penicillium sclerotigenum The degree of green rot severity was evaluated in two yam species, D. alata and D. cayennensis . The causal agentof this disease is the fungus Penicillium sclerotigenum, a highly virulent pathogen on D. cayennensis in the producingareas all over the world. In addition, by cross inoculation, an investigation was conducted on the occurrence of physiologicaladaptations of the fungus relative to its pathogenicity on these species of yams. To complement this study the mycelialgrowth of P. sclerotigenum was evaluated on three culture media, two based on extracts of the yam species examined andthe other one on potato ( Solanum tuberosum ). Dextrose and agar were added to all cultures. The results showed thatgreen rot was less severe on D. alata than on D. cayennensis . No physiological adaptation in relation to the pathogenicityof P. sclerotigenum to both yam species was found. Potato-dextrose-agar and

Sobrevivência de Rotylenchulus reniformis em solo naturalmente infestado submetido a diferentes períodos de armazenamento

The reniform nematode (Rotylenchulus spp.) survives to dissecation better than most plant parasite nematodes, being recorded that R. reniformis survived after 29 months with no host. The aim of this research was to investigate the survival fo R. reniformis in the absence of host, in a naturally infested soil, submitted to different periods of storage, under laboratory conditions. At 45, 90, 135 and 180 days after storage, five soil samples were placed in pots and melon (Cucumis melo) cv. Amarelo Ouro were grown for 80 days under greenhouse conditions. Juveniles, males and imature females in the soil, adult females in root system and total of nematodes (soil+root) were recorded per experimental unit. Linear, logarithmic and quadratic models were tested to describe each variable in relation to storage time. Quadratic models fitted better the variation of all variables except for females in the root system for which the variation did not fit any of the models tested. Nematode populations tended to decrease after 90 days of storage. After 180-days storing soil and subsequently growth of melon in the soil stored, nematode population density at harvest was equivalent to 83.41% of population level at begin of storage.

Pratylenchus brachyurus on Cucumis melo in Brazil

This is the first report in Brazil on the lesion nematode Pratylenchus brachyurus on melon (Cucumis melo) plants in naturally infested soil in Acu-Mossoro belt, Rio Grande do Norte. Morphometric data of the nematode population are presented.

Response of cucurbit species to Rotylenchulus reniformis

The state of Rio Grande do Norte is the major melon (Cucumis melo) producer in Brazil and the reniform nematode Rotylenchulus reniformis has become increasingly important due to damages to that crop and the lack of resistant cultivars and effective control measures. Under these circumstances, eight cucurbit genotypes were screened for resistance or tolerance to a population of R. reniformis in naturally infested field soil, under greenhouse conditions. A high reduction in shoot mass was found in all infected genotypes. Watermelon (Citrullus lanatus) cv. Sugar Baby showed the lowest rate of nematode reproduction.

Control of contaminants during introduction and establishment of Bambusa vulgaris in vitro

The aim of this work was to test techniques to reduce microbial contamination in the phases of introduction and establishment of the in vitro cultivation of Bambusa vulgaris through two experiments. The first experiment was carried out in a completely randomized design using a factorial arrangement (pre-treatment of nodal segments using or not a solution of Derosal 500 SC ® and Chloramphenicol × culture medium with half or full concentration of salts × culture medium with presence or absence of sucrose × culture medium with presence or absence of Plant Preservative Mixture TM ). In a second experiment, carried out in a completely randomized design, the effect of different fungicides associated to Chloramphenicol in a liquid culture medium was tested. It was possible to verify that the isolated effects of the pre-treatment by immersion of the nodal segments in a solution of 4 mL L -1 of Derosal 500 SC ® and 200 mg L -1 of Chloramphenicol for 30 minutes and explants placed in a sucrose-free medium reduced fungal contamination. In the second experiment, the treatment that reduced fungal contamination corresponded to explants placed for seven days in a liquid medium with half the concentration of salts, sucrose-free, with 2 mL L -1 of Plant Preservative Mixture TM and with 4 mL L -1 of Derosal 500 SC ® and 200 mg L -1 of Chloramphenicol.

First report on the occurrence of Scutellonema bradys on Dioscorea alata in Brazil, established in the State of São Paulo

First report on the occurrence of Scutellonema bradys on Dioscorea alata in Brazil, established in the State of Sao Paulo This paper reports the first occurrence of the dry rot on Dioscorea alata in Brazil and the occurrence of this disease and the yam nematode Scutellonema bradys, the causal agent, in the State of Sao Paulo. No Brasil, duas especies de inhame sao as mais utilizadas como culturas alimenticias; Dioscorea cayennensis Lam. e D. alata L. com as respectivas cultivares “da Costa” e “Sao Tome”. A primeira e cultivada no Nordeste e a segunda no norte, sul e centro sul, sendo Sao Paulo o mais importante estado produtor, onde a cultura e conhecida por cara. Nematoides e fungos causam severas doencas do inhame no mundo inteiro, inclusive no Brasil [Moura, 2005. Doencas do Inhame. In: Kimati et. al. (Eds.) Manual de Fitopatologia. v. 2. Doencas das Plantas Cultivadas. Sao Paulo SP. Ceres]. Entre essas, com alto destaque, situa-se a casca preta, conhecida na literatura internacional por dry rot of yam, causada, isoladamente, pelos nematoides Scutellonema bradys Steiner, LeHew & Andrassy, conhecido por the yam nematode, e Pratylenchus coffeae Filipjev & Stekhoven, the lesion nematode, nao havendo referencias sobre infeccoes mistas. Esses patogenos se estabelecem nas raizes de alimentacao e periferia das tuberas comerciais e sementes, aprofundando-se ate 5 cm, Figura 1A. Como consequencias do parasitismo, as tuberas diminuem o volume, peso e a qualidade de mercado. Os fitonematoides provocam tambem ferimentos na epiderme, que sao fatores de predisposicao a incidencia do fungo Penicillium sclerotigenum Yamamoto, agente etiologico da podridao-verde, doenca responsavel por elevadas perdas durante o armazenamento. No Brasil, nao houve, ate o momento, assinalamento da casca preta fora do Nordeste nem em D. alata, estando a doenca restrita a D. cayennensis. Esse fato indicava uma provavel imunidade da cultivar “Sao Tome”, muito embora trabalhos internacionais ja houvessem relatado a suscetibilidade de D. alata em relacao aos nematoides causadores da casca preta, exemplo de Jatala & Bridge, 1990 [Nematode parasites of root and tuber crops. In: Luc et al., (Eds.) Plant Parasitic Nematodes in Subtropical and Tropical Agriculture. Wallingford. CAB International. p. 137] Nesses trabalhos nunca foram mencionados nomes das variedades ou cultivares susceptiveis. Em julho de 2005, foram analisadas dez tuberas de inhame cv. “Sao Tome”, coletadas em campos de producao da empresa Agroexotic Comercio Exterior LTDA, localizados no municipio de Planalto, proximo de Sao Jose do Rio Preto, encaminhadas ao Recife pelo Eng. Agro. Jose Luiz M. Garcia, tecnico da empresa, para analise fitopatologica. Segundo relato dos tecnicos responsaveis pelas coletas, foram identificadas no campo diversas reboleiras que somavam aproximadamente 4 hc, onde haviam evidencias da ocorrencia de casca preta. Apos as extracoes de nematoides de tecidos de tuberas infetadas, as analises morfologica e morfometrica de especimes machos e femeas de um tipo de nematoide encontrado em associacao constante com a doenca confirmaram o diagnostico e permitiram a identificacao do agente causal como sendo o endoparasito migrador S. bradys (Figura 1 B), presente em elevadissimo numero por grama de tecido. Alem de evidenciar um grave problema fitopatologico, provavelmente introduzido por tuberas-sementes contaminadas, este trabalho faz o primeiro assinalamento de S. bradys em D. alata no Brasil e tambem o primeiro das ocorrencias da casca preta e do nematoide S. bradys no Estado de Sao Paulo. FIG. 1 – A. Sintomas externos e internos da doenca casca preta em tuberas comerciais de Dioscorea alata cultivar “Sao Tome”, coletadas no Estado de Sao Paulo; B. Regiao anterior do nematoide Scutellonema bradys.