Ciencias Agropecuarias

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Subject: search.filters.subject.AGENTE CAUSAL

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    Aislamiento y caracterización del agente causal del manchado de la hoja y necrosis del fruto de Capsicum annuum L. en cinco localidades de la Provincia de Tungurahua y una localidad de la provincia de Chimborazo
    (2023-03) López Villacis, María Liliana; Santana Mayorga, Rita Cumandá
    Leaf spotting and fruit necrosis caused by C. fulvum causes chlorotic spots on the upper side of the leaves that turn yellowish as the pathogen progresses and dark spots on the underside that turn olive green, causing partial or total loss of leaves and exposing the fruit to direct sunburn. The fruit shows tan to black lesions that, as the pathogen progresses, form a kind of olive-green velvety mass, causing great economic problems for growers. The objective of this research is to obtain monosporic isolates of the causal agent of leaf spot and fruit necrosis, the characterization of the colonies, the description of morphological characteristics, the inoculation of healthy leaves and fruits, where 106 solutions were made and finally the reisolation from inoculated leaves and fruits. Six monosporic isolates obtained from leaves and six monosporic isolates obtained from fruits were obtained from five localities in the province of Tungurahua (Ambato, Baños, Patate, Pelileo and Mocha) and one locality in the province of Chimborazo (Riobamba), each isolate presenting different characteristics in both leaf and fruit. The morphological characteristics of isolates of C. fulvum showed an average hyphal size of 93.67 µm in isolates obtained from leaves and an average of 99.18 µm in isolates obtained from fruits. The conidiophores with average length of 27.82 µm in isolates from leaves and average of 25.82 µm in isolates from fruits. In conidiophores with average length of 5.11 µm and average width of 3.67 µm in leaf isolates and average length of 5.8 µm and average width of 4.03 µm in fruit isolates. In the inoculation of healthy leaves and fruits, the infection rate was determined in (%) as the first symptoms appear and as the days go by, the leaves and fruits become more contaminated and obtain a higher infection percentage. In the re-isolation, the same colonies of C. fulvum were obtained in leaves and fruits that were harvested at the beginning of the research.
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    Caracterización morfológica, patogénica y molecular del agente causal de la roya blanca en girasol (Helianthus annuus L.)
    (2023-03) Tamayo Morales, Ana Gabriela; Santana Mayorga, Rita Cumandá
    White rust (Pústula helianthicola) of sunflower, discovered in Argentina in 1940, is characterized by the production of pustules on the leaves, with yellow pustules on the adaxial surface and white pustules on the abaxial surface, leading to necrosis of the plant, which affects the yield and quality of the flower head. The objective of the present work was to characterize morphologically, pathogenically and molecularly the causal agent of white rust in sunflower. For the morphological characterization, the sunflower crop was established in a field with a history of white rust, and from the vegetative growth of the crop, the different symptoms and signs were recorded, and later the diameter of pustules, sporangia, oospores and zoospores were observed under the microscope. For pathogenic characterization, healthy leaves of different sunflower varieties (Vincent's Choice, Sunbright Hybrid and Sunrich Orange) were inoculated with a suspension of 104 spores obtained from white rust pustules. For molecular characterization, PCR-amplified fragments of the COX2 (cytochrome C oxidase) gene HelF3/R2 specific for white rust were detected. For the first time in Ecuador, sunflower leaves were described presenting as a symptom the appearance of yellowish pustules in the form of blisters on the adaxial surface of the leaf and later as a sign the appearance of white pustules on the abaxial surface of the leaves, which contained the spores that will spread the disease. The average value of the diameter of the pustules of the sunflower samples with white rust was 29.24 μm. Sporangia reached an average value of 14.81 μm. Zoospores showed an average value of 9.9 μm. Oospores reached an average of 17.6 μm. Hyphae were not found and therefore have no measurements. Inoculation of healthy leaves of different varieties showed that there are significant differences between varieties, detailing that the Vincent's Choice variety is the most susceptible to white rust and the Sunrich Orange variety is the most resistant. Of the sunflower samples with white rust analyzed, the COX2 (cytochrome C oxidase) HelF3/R2 gene was detected in the Montalvo parish of the Tungurahua Province.