Efeito das moléculas Phenyl se Citronellal e o Phenyl S citral na neutralização de enzimas ligadas a patogenicidade de Colletotrichum lindemuthianum: Effect of Phenyl Molecules Citronelal and Phenyl S Citral in the neutralization of enzymes linked to Colletotrichum lindemuthianum pathogenicity

Dentre as doenças mais importantes que afetam a cultura do feijão encontra-se o Colletotrichum lindemuthianum (Sacc. & Magn.) Scrib., agente causal da antracnose, que ocasiona danos econômicos importantes aos produtores em todo o mundo. Acredita-se que enzimas hidrolíticas secretadas por C. lindemuthianum durante a patogênese favoreçam a penetração, a colonização, a obtenção de nutrientes e/ou contribuam para interferir nas reações de defesa do hospedeiro. Assim, este trabalho teve como objetivo avaliar a atividade enzimática ligadas à patogenicidade in vitro, usando médios sólidos específicos tratados com moléculas com potencial antimicrobiano: Phenyl S citral e Phenyl Se Citronelal em três concentrações (g 100 mL-1) 0.25%, 0.0625% e 0.125%. Avaliando a presença de halos de degradação das enzimas amilase, lipase, protease, pectinase, que quando positivos eram mensurados para realização do cálculo de Índice Enzimático (IE). A produção enzimática, o isolado C. lindemuthianum, raça 86, apresentaram performances em quatro das cinco enzimas em estudo, sendo a maior atividade nas enzimas lipase e protease. Concluindo-se que as moléculas testadas são promissoras, já que estão associadas com a redução da atividade de enzimas ligadas a patogenicidade do Colletotrichum lindemuthianum

Fungos fitopatogênicos para biocontrole de Sagittaria montevidensis e seletividade para a cultura do arroz irrigado

The objective of this work was to identify, in the mycobiota of Sagittaria montevidensis, species of pathogenic fungi with potential to act as a bioherbicide, as well as to evaluate their selectivity for irrigated rice crop. The fungi species Fusarium oxysporum and F. semitectum of the mycobiota of S. montevidensis and six spore concentration levels (0, 1x103, 1x104, 1x105, 1x106, and 1x107 spores mL-1), applied on S. montevidensis plants in the stage of one sagittate leaf and on rice plants in the R4 growth stage, were assessed. The progeny of the culture was evaluated. Isolates of F. oxysporum and F. semitectum had greater impact on S. montevidensis plants; however, they were not effective in controlling the species when applied in the seedling stage with one sagittate leaf. The application of F. oxysporum and F. semitectum in the flowering stage of irrigated rice plants causes yield losses, reduction in the vigor of produced seeds, and reduction in root length and plant shoot.O objetivo deste trabalho foi identificar, na micobiota de Sagittaria montevidensis, espécies de fungos fitopatogênicos com potencial bioherbicida, bem como avaliar sua seletividade para a cultura do arroz irrigado. Foram avaliadas as espécies de fungos Fusarium oxysporum e F. semitectum da micobiota de S. montevidensis e seis níveis de concentração de esporos (0, 1x103, 1x104, 1x105, 1x106 e 1x107 esporos mL-1), aplicados sobre plantas de S. montevidensis em estádio de uma folha sagitada e sobre plantas de arroz no estádio de desenvolvimento R4. Avaliou-se a progênie da cultura. Os isolados de F. oxysporum e F. semitectum apresentaram maior incidência sobre as plantas de S. montevidensis; porém, não foram eficazes no controle da espécie quando aplicados no estádio de plântula com uma folha sagitada. A aplicação de F. oxysporum e F. semitectum na fase de floração das plantas de arroz irrigado causa perdas no rendimento, redução no vigor das sementes produzidas e redução no comprimento radicular e da parte área

Combination of biocontrol bacteria for rice seeds microbiolization: incidence and transmission of Bipolaris oryzae, and plant growth

Abstract: Several fungi species are associated with rice seeds, mainly Bipolaris oryzae, since it can kill seedlings and reduce production. Thus, the objective of this research was to study the potential of pre-selected combinations of rhizobacteria [DFs-C4 (DFs185/DFs416/DFs418) and DFs-C5 (DFs306/DFs416/DFs418)], when compared to their use individually (DFs185, DFs306, DFs416, DFs418), besides DFs223, evaluating the effect on the incidence and transmission of B. oryzae, incidence of phytopathogenic fungi and in the initial growth after rice seeds microbiolization. Seeds of cultivars BRS Pelota and BRS Querência (four lots each) were immersed in suspension of these bacteria or in saline solution (control) under agitation (for 30 minutes at 10 ºC). The fungi incidence was evaluated on blotter test. The pathogen transmission was assayed in sterilized vermiculite and humid chamber at 25 ± 2 ºC. After 15 days, the severity of the symptoms and the plant growth were evaluated. For both cultivars, the best treatments were DFs185 and DFs306, reducing the fungi incidence, including B. oryzae, as well as its transmission to seedlings, resulting in seedling length increase. The combination of biocontrol bacteria, individually efficient, did not result in a lower fungi incidence, or a reduction in the transmission of B. oryzae to the seedlings or an initial increase in seedling growth. Therefore, these rhizobacteria are more efficient when used individually

Regional and varietal differences in prevalence and incidence levels of Bipolaris species in Brazilian rice seedlots

A total of 722 rice seed lots were collected at six production regions of Rio Grande do Sul state during three consecutive seasons (2009/10 to 2011/12). For each seed lot, 200 seeds were assessed for the presence of Bipolaris spp. using a standard seed health blotter test. Results showed that B. oryzae and B. cynodontis were found in 62.5% and 10.4% of the seed lots, respectively. Overall mean incidence of B. oryzae and B. cynodontis were 0.5% and 0.06%, respectively. For the two most sampled varieties (75% of the seed lots), IRGA 424 and Puitá INTA CL, mean incidence levels were highest and lowest, respectively. Among regions, infection risk was highest in the southeastern and lowest in the western regions of the state, especially the Fronteira Oeste. The prevalence and the incidence levels of Bipolaris oryzae reported in this study were lower than previous reports in the same region - eighty percent of the seed lots showed incidence levels below the recommended 5% inoculum threshold. In conclusion, rice seeds produced by IRGA-certified growers showed an overall good health quality with regards to B. oryzae infection, which is the main Bipolaris species associated with rice seeds in southern Brazil