Hilário Antônio de Castro

Elaboration and validation of diagrammatic scale to evaluate gray mold severity in castor bean.

ABSTRACT Elaboration and validation of diagrammatic scale to evaluate gray mold severity in castor bean A diagrammatic scale was developed to standardize assessment of gray mold in castor bean bunches, caused by Amphobotrys ricini. Both the maximum and minimum limits of disease severity observed in the field were considered, and the intermediate values progressed by logarithmic increments, representing: 3, 5, 8, 12, 25, 50, 76, 86, 94 and 100% of necrotic area. The scale was validated by 10 raters in three phases: first the raters estimated the severity in 40 photographs without using the scale. In the second and third phases, the same raters estimated the severity in the photographs but with different sequences, with a seven-day interval between assessments. Accuracy, precision, repeatability and reproducibility of estimates were determined by linear regression, relating assessments performed by raters using the scale to actual severity, and relating the results between two assessments using the scale. Assessments with the diagrammatic scale were precise and accurate, the absolute errors were lower than the acceptable limits and the raters exhibited good repetition of estimates. The proposed diagrammatic scale proved to be adequate for severity assessments of gray mold in castor bean.

Diversidade populacional de Colletotrichum sublineolum em seis localidades no Brasil

Foi objetivo deste trabalho caracterizar a populacao de Colletotrichum sublineolum Henn. por meio da avaliacao da virulencia de 289 isolados monosporicos do patogeno. Foram utilizadas como diferenciadoras 10 linhagens elites do programa de melhoramento genetico de sorgo da Embrapa Milho e Sorgo. Os isolados de C. sublineolum foram obtidos de folhas de sorgo provenientes de Palmeira de Goias e Goiânia, GO, Sete Lagoas, Ipiacu e Uberlândia, MG, e Jardinopolis, SP e designados de acordo com um sistema binario de classificacao de racas. As populacoes foram tambem caracterizadas quanto a diversidade fenotipica, por meio de indices de Shannon, de Gleason e de Simpson, e de um indice de complexidade, e quanto a sua distribuicao e frequencia nas seis localidades. Somente a raca 31.04 foi encontrada nos seis locais avaliados e foi a raca mais frequente em Uberlândia, Ipiacu e Palmeira de Goias. A raca mais complexa, 31.31, foi a mais frequente em Sete Lagoas e Goiânia e nao foi observada somente em Palmeira de Goias. Verificou-se que as racas mais frequentes em cada localidade apresentaram-se, em sua maioria, bem distribuidas nas seis regioes avaliadas. O local com maior diversidade fenotipica foi Jardinopolis, de acordo com os indices de Shannon, Simpson e Gleason. O maior indice de complexidade de racas foi encontrado em Sete Lagoas e Goiânia, seguidas por Jardinopolis, Ipiacu, Uberlândia e Palmeira de Goias, respectivamente. Houve correlacao entre os indices de Shannon e Gleason, mas nao entre os indices de diversidade e de complexidade.

Incidência e severidade do mofo-cinzento-da-mamoneira sob diferentes temperaturas, períodos de molhamento e concentração de conídios

The effect of temperature (15, 20, 25 and 28 oC), wetness period (0, 6, 12, 24, 48 and 72 hours) and conidia concentration (0, 1x102, 1x103, 1x104, 1x105 and 1x106 conidia/mL-1) on the incidence and severity of gray mold caused by Amphobotrys ricini in castor bean (Ricinus communis) bunches were evaluated. The conidia concentration effect was evaluated fixing the temperature at 25oC and the wetness duration at 48 hour. The temperature and wetness duration were evaluated fixing the conidial concentration at 1x105 conidia mL-1. The plants were evaluated as to the incidence of fruit wiht symptons and severity in each bunch. The area under incidence progress curve (AUIPC) and under severity progress curve (AUSPC) was calculated, and the results submitted to variance and regression analysis. There was a significant difference for the different concentrations of conidia, for the temperatures and for the wetness period. There was significant interaction between temperature and the wetness period. With the increased concentrations of conidia, both the incidence and the severity of the gray mold showed increases until the 105 conidia mL-1 concentration. There was an increase of AUIPC and AUSPC for the wetness period increase and the temperature. There were no symptoms in the absence of wetness.

Viability of Puccinia psidii urediniospores stored in different environments

The objective of this study was to evaluate the viability and infectivity of urediniospores stored in liquid nitrogen (-196oC), deep-freezer (-80oC), modified-refrigerator (5oC), biochemical oxygen demand (BOD 25oC) and herbarium specimens (25oC), for 150 days. The urediniospores were multiplied in Rose Apple plants (Syzygium jambos) and stored in the above conditions. Every 30 days, the germination and infectivity were evaluated, the first in vitro and the second on Eucalyptus grandis plants. The viability and infectivity of urediniospores stored in BOD and herbarium specimens were not preserved. The maximum germination (24.9%) and infectivity (162 pustules/leaf) occurring in modified-refrigerator environment were higher at 17.6 and 30 days, respectively. Urediniospore germination was highest when preserved in deep-freezer (34.3%) and liquid nitrogen (36.3%), at 45 and 40 days, respectively. The highest infectivity occurred at 60 days for the deep-freezer (77 pustules/leaf) and 90 days for the liquid nitrogen (67 pustules/leaf). Urediniospores kept in deep-freezer, liquid nitrogen, and modified-refrigerator maintained their viability and infectivity for 150 days.

Caracterização e dinâmica de colonização de Cladosporium cladosporioides (Fresen.) de vries em frutos do cafeeiro (Coffea arabica L.)

A presenca de fungos em associacao natural com frutos do cafeeiro e considerada um fator importante influenciando a qualidade do cafe. A influencia negativa de algumas especies de Aspergillus e conhecida, comprometendo inclusive a seguranca do produto. Os relatos de fungos influenciando positivamente a qualidade se resumem a ocorrencia de Cladosporium sp. associados a graos que originaram cafes de boa qualidade, porem informacoes exatas sobre a especie e a sua dinâmica no campo sao escassas. Objetivando caracterizar a especie associada ao cafeeiro e sua dinâmica de colonizacao, 18 isolados de Cladosporium foram caracterizados e identificados. A dinâmica de colonizacao do fungo nas comunidades externa e interna do fruto do cafeeiro foi estudada ao longo do periodo de desenvolvimento do fruto. A especie associada ao cafeeiro foi identificada como Cladosporium cladosporioides (Fresen.) de Vries. A dinâmica do fungo e caracteristica de um fungo saprofita encontrado em intensidade maxima quando os frutos estao nos estagios de cereja.

Management of sorghum anthracnose through diversification of genetic resistance in host population

The aims of the present study were to assess the efficiency of hybrid sorghum mixtures for the management of anthracnose and analyze the virulence diversity and structure in the pathogen populations developed in response to these mixtures. Proportions of 25%, 50% and 75% of the susceptible BRS304 hybrid in relation to the resistant IG150 hybrid were evaluated. Six weekly evaluations of severity were performed. The data were transformed into area under disease progress curve (AUDPC). The isolates of Colletotrichum sublineolum were sampled from hybrid mixtures cultivated in Sete Lagoas and Indianopolis (Brazil) as well as sorghum fields in Rio Verde and Parauna (Brazil). The increase in the proportion of the resistant hybrid in the mixtures led to a reduction in anthracnose severity. The most effective proportions were those with 25% and 50% of the susceptible variety blended with the resistant variety. Complex breeds of C. sublineolum predominated in the populations and a reduction in phenotype diversity was observed. This reduction in diversity was attributed to deviations in the degree of polymorphism in relation to virulence. However, the increase in complex breeds did not imply lesser efficiency on the part of the resistant hybrid in conferring protection to the susceptible hybrid.

Essential oils and whole milk in the control of soybean powdery mildew

This research aimed to evaluate the potential of essential oils (EOs) and cows whole milk (CWM) in order to control soybean powdery mildew and to estimate the most effective concentrations of these natural products in reducing the disease severity on soybean plants. Three experiments were carried out: The first experiment evaluated and selected the most effective treatments to reduce the severity of soybean powdery mildew under greenhouse conditions; the second experiment evaluated the effect of CWM and EOs of citronella, lemongrass, eucalyptus, cinnamon and tea tree on the pathogen through the ultrastructure analysis of soybean leaflets infected by Erysiphe diffusa using the scanning electron microscope (SEM) and light microscope (LM) technology. In the third experiment, the most effective products were tested at several concentrations in order to define the most effective concentrations to reduce disease severity under greenhouse conditions. The treatments CWM (100mL L-1) and EOs of citronella, lemongrass and eucalyptus (1.0mL L-1), reduced the disease severity from 67 to 74%. Direct effects from all natural products tested on the structures of E. diffusa were demonstrated through the SEM and LM analysis. Concentrations at 1.5mL L-1 for EOs of citronella, lemongrass and eucalyptus and also at 180mL L-1 for the treatment CWM were the most effective against E. diffusa on soybean.

Influência da temperatura no desenvolvimento de teliósporos de Phakopsora pachyrhizi em folíolos de soja

The soybean rust can be caused by two fungus species of the genus Phakopsora: P. meibomiae and P. pachyrhizi. The safest method to separate the both species is based on morphologic characteristics of the teliospores. This study was carried out to determine the effect of temperature in telia formation and to observe both telia and teliospore morphometry present in leaflets of soybean plants. Seeds from two soybean cultivars, ´Uirapuru and Pintado‘, were sowed in pots with 3 kg of substrate. Thirty days after sowing, plants on the growth stage V3 were inoculated with urediniospores of P. pachyrhizi and kept in glasshouse for disease development. Upon the appearance of disease symptoms (seven days after inoculation), plants were moved to growth chambers at the temperatures of 10, 15 and 20oC. At fifteen days later, leaflets were observed for the presence of telia and teliopores. Typical pustules containing telia were observed under Sousa, P. F. C., Alves, E., Castro, H. A. Effect of temperature on teliospores development of Phakopsora pachyrhizi in soybean leaflets. Summa Phytopathologica, v.32, n.3, p.227-231, 2006.

Freqüência de ocorrência de agentes etiológicos, sintomas e origem de amostras do cafeeiro catalogados em 12 anos de clínica fitossanitária da UFLA

Situada no sul de Minas Gerais, principal regiao cafeeira do pais, a Clinica Fitossanitaria da Universidade Federal de Lavras tem auxiliado os produtores, dando suporte na diagnose de doencas de origem biotica e abiotica, de modo a gerar subsidios para minimizar as perdas na producao. Nos ultimos doze anos, foram analisadas 378 amostras de cafe. Em 78,6% das amostras, foram detectados fungos, destacando-se Colletotrichum sp. (29%), Rhizoctonia solani (18%), Cercospora coffeicola (13%), Phoma sp. (13%) e Fusarium sp (11%). Ocorreram ainda em numeros representativos casos de fitotoxidez, deficiencia de nutrientes e problemas no sistema radicular. Devido a localizacao da Clinica, a maior parte das amostras foi proveniente de localidades na regiao sul do Estado (63%), seguido do Triângulo Mineiro (12%) e Zona da Mata (10%).

Dez anos da clínica fitossanitária da UFLA - freqüência da ocorrência de patógenos, sintomas e principais hospedeiros

Com o presente trabalho objetivou-se analisar os diagnosticos realizados na Clinica Fitossanitaria do Departamento de Fitopatologia da Universidade Federal de Lavras, no periodo de 1990 a 1999. Foram analisadas 85 especies de hospedeiros, num total de 1429 amostras. Os fungos, com 70,5%, as bacterias, com 12,9% e as viroses, com 1,2%, foram os agentes etiologicos de doencas bioticas encontrados com maior frequencia. A deficiencia nutricional e a fitotoxidez representaram 15,4%. O fungo de maior ocorrencia foi o genero Fusarium, associado a 25,5% das doencas, seguido de Colletotrichum (16%), Rhizoctonia (11%), Alternaria (5%), Cercospora (4%), especies do grupo Helminthosporium (4%) e Phoma (3,5%). Os demais generos de fungos representaram 32% das amostras. Entre os agentes etiologicos bacterianos, destacou-se o genero Erwinia, com 35% das amostras, seguida pelos generos Streptomyces (30%), Ralstonia (13,5%), Pseudomonas (11,5%), Xanthomonas (9,5%) e Agrobacterium (0,5%). As manchas foliares foram os sintomas de maior ocorrencia, encontrados em 40% das amostras recebidas, seguidas das murchas (22%), cancros e sarnas (17%), podridoes (14%) e tombamento (3%). Outros sintomas totalizaram 4% das amostras recebidas. Entre os hospedeiros, as hortalicas destacaram-se com 27% das ocorrencias, os graos, com 24%, as frutiferas tropicais, com 17%, as ornamentais, com 15%, as frutiferas temperadas, com 3%, forrageiras, com 2%, oleaginosas, com 2% e outros, com 10%.