Budding of ascospores in colletorichum lindemuthianum

Abstract

Common bean anthracnose is one of the main fungal diseases that affect the crop. The disease is caused by the fungus Colletotrichum lindemuthianum, anamorph, which has wide variability as well as its teleomorph. Sexual reproduction is the main mechanism of increasing genetic variability in fungi, therefore the study of morphological characteristics and their sexual structures are important. Homothallic strains of the pathogen have shown the production of new ascospores via mitosis after the sexual cycle. As a result of each mitotic division there are two ascospores with amygdaliform and/or allantoid morphology. In this work the characterization of this phenomenon is described as budding. This is the first report on the occurrence of ascospore budding in the genus Colletotrichum. The homothallic strain UFLA84-1 was used. Analyses of light microscopy, fluorescence and high-resolution scanning electron microscopy were used for the description of the budding process. Cytological analyses were carried out to estimate the dimension of ascospores, budding percentage and colony type. The budding cycle is described in six stages, and the complete process develops after the release of all ascospores from an ascus. The ascospores from this process can present both morphologies and bud growth can be apical or lateral. Sexual reproduction is a mechanism of genetic recombination and the budding process increases the number of ascospores generated by meiosis and may therefore represent an adaptive advantage of the pathogen.