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First report of Colletotrichum nymphaeae causing anthracnose on Hass avocados in Brazil.
Oliveira, Vanessa Caroline de; Silva, Hiago Antonio Oliveira da; Mendes, Fabrícia Queiroz; Oliveira, Eduardo Basílio de; Abreu, Lucas Magalhães de; Vieira, Érica Nascif Rufino.
Afiliação
  • Oliveira VC; Universidade Federal de Viçosa, Viçosa, MG, Brazil; vanessa.c.oliveira@ufv.br.
  • Silva HAOD; Universidade Federal de Viçosa, Viçosa, MG, Brazil; hiago.oliveira@ufv.br.
  • Mendes FQ; Universidade Federal de Viçosa, Rio Paranaíba, MG, Brazil; fabricia.mendes@ufv.br.
  • Oliveira EB; Universidade Federal de Viçosa, Viçosa, MG, Brazil; eduardo.basilio@ufv.br.
  • Abreu LM; Universidade Federal de Viçosa, Viçosa, MG, Brazil; lmabreu@ufv.br.
  • Vieira ÉNR; Universidade Federal de Viçosa, Viçosa, MG, Brazil; erica.vieira@ufv.br.
Plant Dis ; 2024 Oct 09.
Article em En | MEDLINE | ID: mdl-39385382
ABSTRACT
The Hass cultivar is one of the most cultivated and distributed avocado varieties throughout the world, having high productivity, nutritional quality, market acceptance and adaptation to different climatic zones (Dreher and Davenport 2013). Anthracnose affects avocado production in tropical and subtropical regions, causing economic losses, especially post-harvest (Fuentes-Aragón et al. 2020). Correct identification of Colletotrichum species causing anthracnose is essential, as different species vary in important phenotypes such as virulence and sensitivity to fungicides (Chen et al. 2016). Twelve samples from batches of avocados with anthracnose were collected in Minas Gerais State, Brazil, in September 2023. The observed symptoms were brown to black depressed circular spots, ranging from a few millimeters to 3 cm in diameter on the epicarp of the fruits, covered in center by mucilaginous layers of pathogen sporulation. Isolation was performed directly from the spore masses and monoconidial isolates were cultured in PDA at 25°C for 7 days for morphological characterization and preserved in sterile water at 4°C. One of the morphotypes commonly recovered from lesions, represented by isolate UCBV 362 (Culture Collection COAD 3843), formed fast-growing colonies having white aerial mycelium and intense salmon-colored sporulation. The cylindrical conidia were 13 to 17.5 µm long and 4.5 to 7 µm wide (average 14.5 x 5.7 µm, N=100), produced on conidiophores dispersed in the aerial mycelium or aggregated on melanized conidiomata formed on the agar. The partial sequence of the second largest subunit of the RNA polymerase II gene (RPB2) from isolate UCBV 362 (GenBank PQ034617, 1116 nt) showed 99% of coverage and 99.37% of nucleotide identity with the RPB2 sequence of the ex-epitype strain of Colletotrichum nymphaeae ICMP 17918 (=CBS 515.78) (GenBank JN985506). In a Maximum Likelihood phylogenetic tree composed with RBP2 sequences from reference strains of the Colletotrichum acutatum species complex, the isolate UCBV 362 formed a highly supported clade with the ex-epitype and other reference strains of Colletotrichum nymphaeae, occupying the Clade 2 of the species complex together with C. scovillae and C. simmondsii (Damm et al. 2012). This result shows the reliability of RPB2 for phylogeny and species delimitation within Colletotrichum. To confirm pathogenicity, 10-mm discs from a 7-day-old colony were inoculated at 3 different points on healthy-looking avocado fruits and incubated at 28°C. Uninoculated fruits served as controls. The first symptoms appeared 5 days after inoculation and were similar to those observed in the original samples, while the fruits in the control group remained asymptomatic. The pathogen was reisolated from the lesions and identified morphologically, fulfilling Koch's postulates. Colletotrichum nymphaeae has been associated with avocado anthracnose in Mexico (Fuentes-Aragón et al. 2020). In Brazil, a study based on molecular phylogeny identified Colletotrichum siamense and C. karsti as etiological agents of this disease (Soares et al. 2021). This report expands the range of species that cause avocado anthracnose in Brazil and provides etiological information for the implementation and monitoring of control methods, especially chemical control.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE País/Região como assunto: America do sul / Brasil Idioma: En Revista: Plant Dis Ano de publicação: 2024 Tipo de documento: Article País de publicação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE País/Região como assunto: America do sul / Brasil Idioma: En Revista: Plant Dis Ano de publicação: 2024 Tipo de documento: Article País de publicação: Estados Unidos