First report of avocado anthracnose caused by Colletotrichum karstii in Mexico

M. G. Velázquez-Del Valle, A. Campos-Martínez, H. E. Flores-Moctezuma, R. Suárez-Rodríguez, J. A. Ramírez-Trujillo, A. N. Hernández-Lauzardo

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Abstract

Avocado fruits (Persea americana Mill.) have high nutritional value and are economicallly important at a global level; however, anthracnose causes significant losses during the pre- and postharvest stages. Colletotrichum gloeosporioides, C. acutatum, and C. boninense have been reported earlier as causal agents for anthracnose in avocado fruits (Silva-Rojas and Ávila-Quezada 2011). Avocado fruits with anthracnose symptoms were monitored during June to July 2013 in orchards cultivated in Morelos, Mexico. Symptoms were visible in the exocarp of the fruits as circular, brown-black spots. The lesions increased up to about 1 cm2 and acervuli were detected on the lesions. Besides, soft rot was observed in the mesocarp. Pure cultures were isolated from diseased fruits. Monoconidial isolates were grown on PDA at 28°C for 7 days. The color of the upper surface of the colony varied from white to gray and the reverse was colorless to pale pink with dark flecks. The conidia were straight and fusiform. To confirm pathogenicity, eight healthy avocado fruits were inoculated with a 1 × 105 conidia/ml suspension. Avocados fruits treated with sterile distilled water served as controls. Avocados fruits were incubated in a moist chamber at 28°C for 7 days. First symptoms appeared three days after the inoculation and were similar to those observed in the field, while the control fruits were symptomless. The phytopathogenic fungus was reisolated from lesions to confirm Koch’s postulates. Genomic DNA was obtained from a 14-days-old pure culture. The fungus was identified molecularly by sequencing the internal transcribed spacer (ITS) region and a fragment of glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene. Both the sequences were deposited in GenBank (Accession Nos. KP729610 and KP729611, respectively). A BLAST search revealed that ITS and GAPDH sequences matched with 99.8% and 100% identity to Colletotrichum karstii (JX625157.1 and JQ247605.1, respectively). Given its symptoms on fruits, fungal morphology, and sequence results (ITS and GAPDH), the pathogen was identified as C. karstii, which belongs to the C. boninense species complex (Damm et al. 2012). C. karstii was previously described from Orchidaceae in China (Yang et al. 2011) and it was also reported in Brazil affecting mango and apple fruits (Lima et al. 2013; Velho et al. 2014). To our knowledge, this is the first report of avocado anthracnose caused by C. karstii. The diversity of Colletotrichum spp. found in Mexico is probably related to the origin of the avocado.

Original languageEnglish
Pages (from-to)534
Number of pages1
JournalPlant Disease
Volume100
Issue number2
DOIs
StatePublished - Feb 2016

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