Bitter rot (BR), caused by Colletotrichum spp., is one of the prevalent fungal diseases of apple worldwide. Some Colletotrichum spp. also causes Glomerella leaf spot (GLS). The presence of BR was recorded in 2014 in the central region of Santa Fe, and leaf spots (LS) began to be seen in 2016 in three low-chill apple cultivars, ‘Eva’, ‘Princesa’ and ‘Caricia’. This thesis was focused to characterized the Colletotrichum species involved in these pathologies, studying aspects of epidemiology and pathogenesis and determined the sensitivity of isolates to fungicides. Thirty-four isolates from symptomatic fruits and leaves were obtained. Morphological characteristics in combination with multilocus analysis revealed that Colletotrichum siamense is the single species associated with BR and LS on low-chill apples in Santa Fe. Of the three cultivars evaluated, ‘Caricia’ was the most susceptible to BR. The registered LS have notable differences with typical GLS revealing that this disease is no present in the region. It was also determined that C. siamense survives in the form of conidia, mainly on the plant, and that it uses a hemibiotrophic mechanism to infect fruits and leaves. The isolates of C. siamense are sensitive to fungicides belonging to the methyl benzimidazole carbamate and demethylation inhibitors groups. These findings will be useful for future studies of sensitivity to fungicide in the field and to design management strategies for diseases caused by C. siamense in the region.
Bitter rot (BR), caused by Colletotrichum spp., is one of the prevalent fungal diseases of apple worldwide. Some Colletotrichum spp. also causes Glomerella leaf spot (GLS). The presence of BR was recorded in 2014 in the central region of Santa Fe, and leaf spots (LS) began to be seen in 2016 in three low-chill apple cultivars, ‘Eva’, ‘Princesa’ and ‘Caricia’. This thesis was focused to characterized the Colletotrichum species involved in these pathologies, studying aspects of epidemiology and pathogenesis and determined the sensitivity of isolates to fungicides. Thirty-four isolates from symptomatic fruits and leaves were obtained. Morphological characteristics in combination with multilocus analysis revealed that Colletotrichum siamense is the single species associated with BR and LS on low-chill apples in Santa Fe. Of the three cultivars evaluated, ‘Caricia’ was the most susceptible to BR. The registered LS have notable differences with typical GLS revealing that this disease is no present in the region. It was also determined that C. siamense survives in the form of conidia, mainly on the plant, and that it uses a hemibiotrophic mechanism to infect fruits and leaves. The isolates of C. siamense are sensitive to fungicides belonging to the methyl benzimidazole carbamate and demethylation inhibitors groups. These findings will be useful for future studies of sensitivity to fungicide in the field and to design management strategies for diseases caused by C. siamense in the region.
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