Morphological characterization and molecular identification of Colletotrichum nymphaeae associated with Juglans regia fruit

Abstract

Juglans regia L., known as Persian walnut, is native to central Asia, where plantations are spread over several countries. The species has a certain importance to humanity, e.g. high quality of the wood. However, the main purpose of cultivation is to obtain edible nuts. In Brazil, the fungus Colletotrichum nymphaeae has significantly damaged the fruit and consequently affected the nut production. Thus, the objective of this study was to verify the pathogenicity and identify, morphologically and molecularly, isolates of Colletotrichum spp. collected from fruit with anthracnose symptoms. The pathogenicity was evaluated in detached fruit and, concerning the morphological characterization, the fungal colonies were grown in Mathur culture medium. The actin region of DNA was used for molecular identification. The isolates of Colletotrichum spp. caused anthracnose symptoms to J. regia fruit. The morphological characteristics of the isolates were similar to those found in species from the Colletotrichum acutatum complex, including the C. nymphaeae. By sequencing the actin genomic region, we confirm that the causal agent of anthracnose in J. regia fruit was Colletotrichum nymphaeae.