Mario Sobral de Abreu

Estudos histopatológicos de Colletotrichum spp. em plântulas de cafeeiro

The objective of this work was to follow the process of infection, colonization and reproduction of different isolates of Colletotrichum spp. in coffee plantlets, obtained by embryo culture, using scanning electron microscopy. The embryo explants were obtained from coffee seeds cv. Rubi. Plants produced in vitro were inoculated with 5µL of a 106 conidia.mL-1 spore suspension, on the hypocotyl region and leaves, wounding with an entomological needle. Isolates of Colletotrichum gloesporioides were obtained from stem (IS) and leaves (IL) from plants with symptoms of greasy leaf spot, and from mangos with symptoms of anthracnose (IM). Isolates of Colletotrichum dematium were obtained from healthy coffee plants. Three hours after inoculation (h.a.i.), leaves and hypocotyl fragments were transferred to 1.5mL-microtubes containing modified Karnovskys fixative solution. Further samples were collected at 3, 5, 12, 16, 24, 48, 72, 96, 114 and 144 h.a.i. Conidia of all isolates adhered more frequently in the depressions of hypocotyls and guard-cells, forming a septum 5 h.a.i. Germ tubes were observed 12 h.a.i. starting from the extremities as well as laterally in the conidia. Appressoria were produced by C. dematium (globoses, trilobullated and foot and comma-shaped), and C. gloeosporioides, respectively globoses, 24 h.a.i. C. gloeosporioides (IH and IF) produced conidiogenic cells 48 h.a.i. Acervuli were produced 72 h.a.i. by C. gloeosporioides (IH), 96 h.a.i. by C. dematium. C. gloeosporioides isolated from mango colonized coffee plant tissues, producing conidiogenic cells without production of acervuli. The most aggressive isolates were IS and IL.

Fungos associados a grãos de cinco cultivares de café (Coffea arabica L.)

ABSTRACT – (Fungi associated with coffee beans ( Coffea arabica L.) on fi ve cultivars). The aim of this work was to verify the mycobiota associated both internally and externally with coffee beans on the cultivars “Catuai Amarelo”, “Mundo Novo”, “Acaia,” “Rubi” and “Icatu” a nd detect the occurrence of ochratoxin A in these samples. Coffee fruits were harvested on the EPAMIG experiment farm, situated in Lavras /Minas Gerais. The procedure for fungi analysis was the Blotter test. Determination of ochratoxin A was accomplished by HPLC. Fusarium semitectum was identifi ed only on the Icatu cultivar and F. equiseti was identifi ed on all cultivars except Mundo Novo. Three species of Penicillium were isolated from the beans: P. rugulosum on the Rubi cultivar, P. funiculosum on the Icatu cultivar and P . variabile on the others. The Acaia cultivar had the highest incidence of P . variabile followed by Mundo Novo and Catuai. The occurrence of A. niger and A. ochraceus did not differ among the cultivars.The presence of fungi on the surface was signifi cantly higher than inside the beans. None of the samples presented ochratoxin A.

Nutrients distribution in diseased coffee leaf tissue

Knowing the structure and distribution of nutrients in plant tissues can clarify some mechanisms of pathogen attack in plants and plant defense against infection, thus helping management strategies. The aim of this study was verify differences in distribution of mineral nutrients in coffee leaf tissues around foliar lesions of bacterial blight of coffee, blister spot, cercospora leaf, phoma leaf spot and coffee leaf rust. Fragments of leaf tissue surrounding the lesions were dehydrated in silica gel, carbon covered and subjected to X-ray microanalysis (MAX). Thirty-three chemical elements were detected in leaf tissue; however, there was variation in potassium and calcium contents surrounding the lesions. The highest potassium content was found in asymptomatic tissues surrounding the lesions, decreasing toward the transition zone and reaching minimum content in symptomatic tissues. The highest calcium content was found in symptomatic tissues, decreasing toward the transition zone and reaching minimum content in asymptomatic tissues. Therefore, MAX can be used to analyze the composition and distribution of nutrients in plant tissues and, if associated with mineral nutrition, it may help understand host-pathogen relationships and plant disease management.

Análise da dinâmica, estrutura de focos e arranjo espacial da mancha manteigosa em campo

Objetivou-se estudar a dispersao espacial da mancha manteigosa em cafeeiro, por meio de arranjos espaciais e da analise da dinâmica e estruturas de focos da doenca durante tres anos consecutivos. Nesse periodo, nao houve progresso da doenca no campo. Sob plantas doentes, surgiam mudas com sintomas da doenca, um indicio da transmissibilidade via semente. Constatou-se um total de 10 focos, com media de 2,5 plantas/focos e com tendencia desses focos (maior numero de plantas sintomaticas) na direcao das linhas de plantios, tendo disposicao de forma eliptica. Observou-se numero elevado de focos unitarios, correspondendo a 52% das plantas doentes. Pelas analises de sequencias ordinarias runs e doublet verificou-se padrao espacial aleatorio. Tal fato indica que a mancha manteigosa ocorre a partir de plantas isoladas (focos unitarios) e que a principal via de transmissao e a semente (semente/planta/semente).

ESTUDOS HISTOPATOLÓGICOS DA INTERAÇÃO COLLETOTRICHUM GLOEOSPORIOIDES - CAFEEIRO

In studies involving the interaction Colletotrichum gloeosporioides - coffee trees (Coffea arabica L.) there is little information regarding the pre-penetration, penetration and colonization pathways of this pathogen. The objectives of this work were: 1. to study through scanning electron microscopy (SEM) the pre-penetration and penetration events of C. gloeosporioides in hypocotyls of coffee plantlets; 2. to observe the colonization of Colletotrichum spp. in branches and fruits of coffee trees with blister spot symptoms. The study took place in three trials. In the first trial, it was observed and reported the pre-penetration events of C. gloeosporioides inoculated on hypocotyls of coffee cv. Acaia Cerrado with and without wounds. The second trial was performed to investigate the colonization of diseased coffee branches that presented drastic wilt and local necrosis was observed. Finally the third trial investigated the colonization of this pathogen in diseased coffee fruits. When C. gloeosporioides was inoculated, germination could be observed in wounded hypocotyls 6 hours after inoculation. Better adhesion of conidia was evident at surface depressions of hypocotyls and germination started by emission of one or two terminal germ tubes. Round or sub-round shaped apressoria appeared 12 hours after inoculation. Up to 72 hours, acervula formation was not observed on inoculated tissues. The wilted branches presented colonization in the phloem and cortical tissues. In fruits at different stages of maturation, it was observed colonization in tissues near the epidermis and collapse of the stomata in the affected area.In studies involving the interaction Colletotrichum gloeosporioides - coffee trees (Coffea arabica L.) there is little information regarding the pre-penetration, penetration and colonization pathways of this pathogen. The objectives of this work were: 1. to study through scanning electron microscopy (SEM) the pre-penetration and penetration events of C. gloeosporioides in hypocotyls of coffee plantlets; 2. to observe the colonization of Colletotrichum spp. in branches and fruits of coffee trees with blister spot symptoms. The study took place in three trials. In the first trial, it was observed and reported the pre-penetration events of C. gloeosporioides inoculated on hypocotyls of coffee cv. Acaia Cerrado with and without wounds. The second trial was performed to investigate the colonization of diseased coffee branches that presented drastic wilt and local necrosis was observed. Finally the third trial investigated the colonization of this pathogen in diseased coffee fruits. When C. gloeosporioides was inoculated, germination could be observed in wounded hypocotyls 6 hours after inoculation. Better adhesion of conidia was evident at surface depressions of hypocotyls and germination started by emission of one or two terminal germ tubes. Round or sub-round shaped apressoria appeared 12 hours after inoculation. Up to 72 hours, acervula formation was not observed on inoculated tissues. The wilted branches presented colonization in the phloem and cortical tissues. In fruits at different stages of maturation, it was observed colonization in tissues near the epidermis and collapse of the stomata in the affected area.

Efeito da temperatura no crescimento micelial, produção e germinação de conídios de Colletotrichum spp. isolados de Coffea arabica L

The objective of this study was to assess the effect of temperature on micelial growth, production and conidial germination of Colletotrichum spp. isolates from branches, leaves and fruits of coffee with symptoms of blister spot and tip blight. The isolates presented differentiated behavior regarding the speed of mycelial growth, sporulation capacity and the formation of reproductive structures, showing high capacity of adaptation to different temperatures.

Estudos histoplásticos da interação Colletotrichum gloeosporioides: cafeeiro

In studies involving the interaction Colletotrichum gloeosporioides - coffee trees (Coffea arabica L.) there is little information regarding the pre-penetration, penetration and colonization pathways of this pathogen. The objectives of this work were: 1. to study through scanning electron microscopy (SEM) the pre-penetration and penetration events of C. gloeosporioides in hypocotyls of coffee plantlets; 2. to observe the colonization of Colletotrichum spp. in branches and fruits of coffee trees with blister spot symptoms. The study took place in three trials. In the first trial, it was observed and reported the pre-penetration events of C. gloeosporioides inoculated on hypocotyls of coffee cv. Acaia Cerrado with and without wounds. The second trial was performed to investigate the colonization of diseased coffee branches that presented drastic wilt and local necrosis was observed. Finally the third trial investigated the colonization of this pathogen in diseased coffee fruits. When C. gloeosporioides was inoculated, germination could be observed in wounded hypocotyls 6 hours after inoculation. Better adhesion of conidia was evident at surface depressions of hypocotyls and germination started by emission of one or two terminal germ tubes. Round or sub-round shaped apressoria appeared 12 hours after inoculation. Up to 72 hours, acervula formation was not observed on inoculated tissues. The wilted branches presented colonization in the phloem and cortical tissues. In fruits at different stages of maturation, it was observed colonization in tissues near the epidermis and collapse of the stomata in the affected area.In studies involving the interaction Colletotrichum gloeosporioides - coffee trees (Coffea arabica L.) there is little information regarding the pre-penetration, penetration and colonization pathways of this pathogen. The objectives of this work were: 1. to study through scanning electron microscopy (SEM) the pre-penetration and penetration events of C. gloeosporioides in hypocotyls of coffee plantlets; 2. to observe the colonization of Colletotrichum spp. in branches and fruits of coffee trees with blister spot symptoms. The study took place in three trials. In the first trial, it was observed and reported the pre-penetration events of C. gloeosporioides inoculated on hypocotyls of coffee cv. Acaia Cerrado with and without wounds. The second trial was performed to investigate the colonization of diseased coffee branches that presented drastic wilt and local necrosis was observed. Finally the third trial investigated the colonization of this pathogen in diseased coffee fruits. When C. gloeosporioides was inoculated, germination could be observed in wounded hypocotyls 6 hours after inoculation. Better adhesion of conidia was evident at surface depressions of hypocotyls and germination started by emission of one or two terminal germ tubes. Round or sub-round shaped apressoria appeared 12 hours after inoculation. Up to 72 hours, acervula formation was not observed on inoculated tissues. The wilted branches presented colonization in the phloem and cortical tissues. In fruits at different stages of maturation, it was observed colonization in tissues near the epidermis and collapse of the stomata in the affected area.

Efeito In vitro e In vivo de filtrados de rizobactérias sobre Colletotrichum gloeosporioides Penz. do cafeeiro

Objetivou-se avaliar o efeito de filtrados derivados de culturas de rizobacterias na inibicao da germinacao de esporos de Colletotrichum gloeosporioides e confirmar sua acao antifungica em relacao a mancha manteigosa em mudas de cafeeiro. Foram conduzidos ensaios in vitro para testar 42 filtrados, identificando-se os de maior capacidade de inibir a germinacao de esporos do fungo. Plântulas de cafe foram submetidas a inoculacao com Colletotrichum e pulverizacao com quatro dos filtrados mais promissores. Os tratamentos constituiram um fatorial 4x4+2, combinando a aplicacao de quatro filtrados com quatro modos de inoculacao do fungo (ausencia de inoculacao e inoculacao dois dias antes, junto, ou dois dias depois da aplicacao dos filtrados). Uma testemunha absoluta e outra que recebeu somente o inoculo do fungo constituiram tratamentos adicionais. Apos 35 dias, foram avaliados o crescimento do cafeeiro e a severidade da mancha manteigosa. Os filtrados apresentaram ampla variacao quanto a atividade antifungica in vitro e cinco deles inibiram completamente a germinacao dos esporos. No experimento com planta, os filtrados tiveram eficacia similar contra a mancha manteigosa, com controle parcial da doenca (35%). A aplicacao dos filtrados teve efeito depressivo ao crescimento do cafeeiro, proporcionando menor producao de materia seca em relacao a testemunha absoluta.

Incidência de Colletotrichum spp. em frutos de Coffea arabica L. em diferentes estádios fisiológicos e tecidos do fruto maduro

Especies de Colletotrichum estao presentes em todos os orgaos do cafeeiro. A importância desses fungos para a cultura do cafeeiro ainda e muito discutida, pois tratam-se de populacoes de especies de Colletotrichum ocasionando diversos sintomas ou colonizando as plantas de forma endofitica. O estudo foi realizado com o objetivo de verificar a presenca de Colletotrichum spp. em diferentes estadios de desenvolvimento do fruto de cafeeiro e nos tecidos do exocarpo+mesocarpo, endocarpo e endosperma de frutos maduros. Este trabalho foi realizado no Laboratorio de Diagnose e Controle de Enfermidades de Plantas da Universidade Federal de Lavras-(UFLA). Os frutos foram coletados na area experimental do Setor de Cafeicultura da UFLA com cafeeiros das cultivares Catuai Vermelho, Catuai Amarelo, Icatu, Topazio, Katipo, Rubi, Acaia Cerrado e Mundo Novo. Nos estadios de formacao do fruto, verificaram-se altos valores de incidencia, com media de 86,6%. Em relacao as cultivares, as maiores incidencias foram em Topazio e Rubi, ambas com 94,4% e as menores incidencias nas cultivares Icatu e Mundo Novo, com 72,8% e 78,4%, respectivamente. A incidencia de Colletotrichum spp. variou tanto entre cultivares como entre os tecidos do fruto. No exocarpo+mesocarpo, as cultivares Topazio, Rubi e Acaia Cerrado tiveram porcentagens de colonizacoes de 84,72%, 79,16% e 77,77%, respectivamente, enquanto a cultivar Icatu teve 48,6%. No endocarpo, a maxima colonizacao foi de 9,72% na cultivar Rubi e a menor colonizacao na cultivar Acaia Cerrado, com 1,39%. No endosperma, a cultivar Rubi teve novamente o maior indice de colonizacao (8,33%) e as cultivares Mundo Novo e Katipo ambas com 1,39% de colonizacao. Verificou-se a presenca de Colletotrichum spp. nas sementes de todas as cultivares estudadas.

Transmissibilidade e efeito do tratamento de sementes de cafeeiros com mancha manteigosa (C. gloeosporioides)

Neste trabalho, os objetivos foram avaliar a transmissibilidade de C. gloeosporioides mancha manteigosa (MM) em sementes e estudar o efeito do tratamento por fungicidas no controle do referido patogeno. Colheram-se frutos cerejas em plantas doentes e sadias, procedeu-se o despolpamento manual secando as sementes a sombra, retirou-se o endocarpo e, em seguida, realizaram-se os devidos tratamentos (fungicida) semeando-as em areia esterilizada. Avaliaram-se os sintomas de necrose e morte das plântulas e a incidencia de C. gloeosporioides, por meio do teste de incubacao em substrato de papel (blotter test), em sementes de cafeeiro tratadas e nao tratadas com mistura comercial de benzimidazol+dimetilditiocarbamato (dose i.a. de 45 g+105 g/100 kg sementes). Com o desenvolvimento das plântulas, observaram-se em sementes de plantas com MM , altos indices de morte de plântulas, tendo apenas 5,2% de sobrevivencia, porem, com a abertura dos primeiros foliolos observaram-se, nestas plântulas, sintomas tipicos da doenca, com posterior morte das mesmas, enquanto que, a partir de sementes sadias, as plântulas apresentam-se vigorosas e em pleno crescimento. Ja, com o uso do tratamento fungicida, observou-se efeito significativo, principalmente em sementes de plantas doentes (MM), nas quais verificou-se uma menor area abaixo da curva de progresso da doenca e, consequentemente, menor incidencia e severidade da doenca. Pelo bloter test, em sementes tratadas, nao houve crescimento de nenhum agente fungico tanto para sementes de plantas com MM como para sementes de plantas sadias. Em sementes nao tratadas, observou-se incidencia de C. gloeosporioides em 29,8% nas sementes de plantas com MM e 1,2% de incidencia em sementes de plantas sadias. Com base nestes resultados, fica evidenciado que neste patossistema, mancha manteigosa - cafeeiro, a principal via de transmissao de C. gloeosporioides e a semente.