Rafael Galbieri

Eficiência da disseminação aérea em Pyricularia grisea

Pyricularia grisea (teleomorph Magnaporthe grisea) infects more than 80 gramineous plants. In Brazil, it attacks important crops like rice and wheat causing blast disease. Recently the disease was reported in triticale, an alternative crop to wheat producers in Southern Sao Paulo state. Airborne conidia are one of the most important way of dissemination, although little reliable information is available on the distance traveled by spores from an inoculum source. The present work aimed to determine by molecular tools the efficiency of aerial dissemination of P. grisea from a known inoculum source. The presence of pathogen clones in fields distant 4, 30 and 1000 meters from an infected field suggested that spores can travel at least these distances.

Phenotypic variability among isolates of Ramularia areola from Brazilian cotton

There is a lack of information about the level of resistance of cotton genotypes to a wider range of Ramularia areola isolates occurring across the cotton growing areas of Brazil. For this purpose, firstly it is necessary to know the existence or not of genotypic and phenotypic variability among the R. areola isolates from different geographical origins. The objective of the present investigation was to verify the existence of phenotypic variability among 23 R. areola isolates collected from six cotton growing states of Brazil. Two resistant genotypes, FMT 02102996 and CNPA BA 2003-2059, and the susceptible genotype FMT 701 were individually inoculated with 23 R. areola isolates under glasshouse conditions and the severity of infection was evaluated 30 days after inoculation. Genotypes CNPA BA 2003-2059 and FMT 02102996 were susceptible to three isolates and resistant to the rest of the isolates. Genotype FMT 701 was susceptible to all the isolates except the isolates 22.3 and 42.7. Results indicate the existence of variability among R. areola isolates and that the three genotypes are useful in distinguishing phenotypic variability within isolates of this pathogen.

Reação de genótipos de algodoeiro à mancha de Ramularia em diferentes épocas e ambientes

Cotton genotypes, comprising cultivars and advanced lineages, were evaluated for their reaction to areolate mildew (Ramularia areola) in field experiments under natural infestation, at 60, 90 and 110 days after plant emergence in Ituverava-SP, and at 75, 100 and 120 days in Primavera do Leste-MT. In both localities, the latest evaluation was fundamental to adequately discriminate the genotypes and determine their effective degree of resistance to the pathogen. The earliest evaluations were inefficacious for this or underestimated the susceptibility of some genotypes. Highly significant genotype x environment interaction and extremely low, non-significant correlation between the mean scores of genotypes in the two experiments expressed contradictory performance of some genotypes, according to the locality, indicating possible existence of genetic variability of this pathogen in Brazil.

Ramularia areola sporulation potential in Brazilian cotton

A mancha de ramularia causada por Ramularia areola e uma das mais importantes doencas para a cultura do algodoeiro no Brasil. Para o controle efetivo da doenca, sao necessarias 5-9 aplicacoes de fungicidas em cultivares suscetiveis. O objetivo do presente trabalho foi avaliar, in vitro e in vivo, o potencial de esporulacao de isolados de R. areola, originarios de diferentes regioes do Brasil, sob diferentes regimes de temperaturas. A producao de esporos foi avaliada em laboratorio e em folhas de plantas de oito cultivares de algodoeiro em condicoes de casa-de-vegetacao. Os resultados obtidos in vitro indicaram que o potencial de producao de esporos foi dependente da temperatura. A maxima esporulacao do fungo ocorreu com 17oC para isolados originarios do Estado de Sao Paulo e 23oC para isolados de Goias e Mato Grosso. No estudo in vivo, houve variacao na esporulacao em funcao da cultivar e do isolado. A maioria dos isolados apresentou alta agressividade na cultivar FM 966 LL e DELTAOPAL. Com os resultados obtidos, e possivel indicar uso mais racional de fungicidas, cultivares que apresentaram menor esporulacao do fungo, alem de formar base para novos estudos com relacao a variabilidade desse fungo em algodoeiro no Brasil. Esse e o primeiro relato sobre o potencial de esporulacao de isolados brasileiros de R. areola.

Desempenho de genótipos de algodoeiro na presença ou não de rotação de cultura com Crotalaria spectabilis, em área infestada com Meloidogyne incognita

In an area naturally infested with Meloidogyne incognita race 3, located in Primavera do Leste, Mato Grosso State, Brazil, the performance of 21 cotton genotypes having different levels of tolerance to this parasitic nematode was studied, in the presence or absence of crop rotation with Crotalaria spectabilis. A general trend was observed for crop rotation to reduce the severity of symptoms exibited by plant sowing to nematode incidence, and lead to increased cotton yield. However, its effect was not sufficient to increase the performance of genotypes with low tolerance to the parasite, which, even under the crop rotation schem, had disease sympton rates that were 142% higher and cotton yields that were 57% lower than those obtained for more tolerant genotypes. High correlation between average yield in the presence or absence of crop rotation, and absence of interaction between genotype and crop rotation, indicated that, although at higher yield level being achieved, the tendency of genotype performance remained the same in both systems. The yield of the three more tolerant genotypes in the absence of crop rotation was 48% superior to that of the three least tolerant genotypes under crop rotation. The minimum possible losses, attributable to the use of susceptible genotypes, were estimated at 37% and 29%, respectively, without crop rotation being used or under conditions of crop rotation.

Reação de cultivares de algodoeiro a Meloidogyne incognita em condições de campo e casa de vegetação no estado de Mato Grosso

Genotipos de algodoeiro, compreendendo cultivares e linhagens avancadas, foram avaliados no Estado de Mato Grosso quanto a reacao a Meloidogyne incognita. Em dois experimentos de campo, foi avaliada a tolerância a esse nematoide mediante atribuicao de notas, de acordo com sintomas externos exibidos pelas plantas. Um ensaio avaliou tambem a resistencia ao parasita, mediante determinacao do numero de especimes nas raizes de plantas amostradas nas parcelas. A resistencia foi avaliada tambem em casa de vegetacao, por meio da determinacao do numero de massas de ovos nas raizes e do fator de reproducao. Foram constatadas diferencas notaveis na reacao dos 22 genotipos estudados, verificando-se a formacao de grupos graduais de desempenho, tanto com respeito a resistencia quanto a tolerância. Nas duas caracteristicas, destacaram-se positivamente as cultivares IAC 25 RMD, IPR 140 e IPR JATAI, e negativamente, dentre outras, FIBERMAX 966, LDCV FREGO e FMT 703. A producao de algodao em caroco variou de 482 a 3087 g/parcela no experimento de Campo Verde, e de 1153 a 3151 g/parcela no de Primavera do Leste. As perdas na producao, nos genotipos mais afetados, foram de ate 65% no primeiro experimento e de ate 40% no segundo. Os dados de avaliacao da resistencia e da tolerância mostraram-se correlacionados, porem, os da tolerância, a julgar pelos coeficientes de variacao e de correlacao intra-classe, na analise da variância, mostraram-se mais precisos e de maior repetibilidade.

Influência da colheita e períodos de armazenamento na qualidade sanitária de sementes de mamoneira

As atuais preocupacoes quanto a escassez das reservas de petroleo e o agravamento do efeito estufa, pela emissao de CO2, levam a cultura da mamona a ser uma das fontes para energia renovavel. Sabe-se que ao longo do ciclo da mamona sao produzidos racemos de varias ordens, que se desenvolvem sob diferentes condicoes ambientais, podendo provocar variacoes na qualidade das sementes. Assim, objetivou-se avaliar a interferencia da colheita e de cinco periodos de armazenamento na qualidade sanitaria das sementes de mamona, cultivar IAC-2028. Para tanto, foram instalados os testes de germinacao e sanidade, logo apos a colheita e aos 3; 6; 9 e 12 meses de armazenamento em condicoes nao controladas de temperatura e umidade relativa do ar. As avaliacoes foram feitas em esquema de parcela subdividida no tempo, onde as parcelas foram constituidas por cinco epocas trimestrais de avaliacao e as sub-parcelas por 11 tratamentos. Os resultados sugerem que todos os racemos podem ser colhidos em uma unica etapa, sem que ocorram perdas de qualidade das sementes.

Avaliação de genótipos de algodoeiro para resistência a Verticillium dahliae

ABSTRACT Cotton genotypes, comprising the main cultivars and somebreeding lines available in Brazil, were evaluated under greenhouseconditions for the resistance to Verticillium wilt. In order to establishadequate conditions for re sistance expression, experiments examiningisolate pathogenicity and the most appropriate inoculum concentrationwere carried out first. Based on the obtained data, 25 genotypes werethen inoculated by the “dipping” method at 10 6 spores/mL inoculum Galbieri, R.; Cia, E.; Fuzatto, M.G.; Ito, M.F.; Luders, R.R.; Kondo, J.I. Cotton genotypes evaluation for resistance to V erticillium dahliae . Summa Phytopathologica, v.34, n.3, p.211-215, 2008 Additional keywords: Verticillium wilt, concentration inoculum, Gossypium hirsutum concentration and the plants were evaluated by considering both internaland external disease symptoms. Significant differences in resistance levelwere observed among the genotypes. Deltaopal, IAC 04/236, IAC 04/259, PR 0136 and Fibermax 966 were more resistant and Coodet ec 401,Distak, Coodetec 410 and EPAMIG 0316 more susceptible. Evaluationmethod was efficient by observing both internal and externalsymptoms, and the correlation between them was r = + 0,85**.