Environmental requirements for infection of Colletotrichum acutatum and C. gloeosporioides sensu lato in citrus flowers and prevalence of these pathogens in Brazil

Autor(es)

Goncalves, Fabricio Packer ^{[1, 2]} ; Nogueira Junior, Antonio F. ^[1] ; Silva-Junior, Geraldo Jose ^[3] ; Ciampi-Guillardi, Maisa ^[1] ; Amorim, Lilian ^[1]

Afiliação do(s) autor(es)

^[1] Univ Sao Paulo, Dept Fitopatol & Nematol, Escola Super Agr Luiz de Queiroz ESALQ, BR-13418900 Piracicaba, SP - Brazil

^[2] Corteva Agrisci, BR-13800970 Sao Paulo - Brazil

^[3] Fundo Def Citricultura Fundecitrus, Dept Pesquisa & Desenvolvimento, BR-14807040 Araraquara, SP - Brazil

• Tipo de documento: Artigo Científico
• Fonte: European Journal of Plant Pathology; v. 160, n. 1 FEB 2021.
• Citações Web of Science: 0

Resumo

Citrus post-bloom fruit drop (PFD) is caused by Colletotrichum acutatum and C. gloeosporioides species complexes and frequently occurs in Sao Paulo (SP) state, Brazil. The environmental requirements for conidial germination and appressorium formation have been already determined in vitro; however, the environmental conditions for infection in citrus flowers remain unknown. C. acutatum is considered the main species complex causing PFD in citrus, but a survey of the pathogen's prevalence has never been performed in SP state. The aims of this study were to assess the influence of different temperatures and wetness periods on infection of flowers by C. acutatum and C. gloeosporioides in potted citrus trees, and to determine the prevalence of both pathogens in different SP regions and sweet orange varieties. Environmental requirement trials were conducted in 2- to 3-year-old potted sweet orange trees. Flowers at different development stages (R2, R4 and R5) were inoculated with C. acutatum and C. gloeosporioides, and the trees were incubated at 18 or 24 degrees C for wetness periods of 6, 8, 12, 16 or 24 h. The percentages of inoculated flowers with PFD lesions and persistent calyces were calculated. The prevalence of both pathogens in SP regions was assessed in samples of diseased flowers collected at 16 commercial orchards of `Natal', `Valencia' and `Pera' sweet oranges. The species complex was confirmed by isolation and PCR with species complex-specific primers. Blossom blight and persistent calyx incidences were higher in flowers inoculated with C. acutatum than in those inoculated with C. gloeosporioides. Incubation periods ranged from 2 to 5 days, and from 5 to 6 days for C. acutatum and C. gloeosporioides, respectively. In SP, irrespective of the region and sweet orange variety, C. acutatum was isolated from more than 80% of symptomatic flowers. We concluded that C. acutatum is not only more aggressive than C. gloeosporioides for causing PFD but also more prevalent in SP orchards. (AU)

• Processo FAPESP: 08/54176-4 - Epidemiologia molecular e manejo da podridão floral dos citros em áreas de expansão da cultura no estado de São Paulo
• Beneficiário: Lilian Amorim
• Modalidade de apoio: Auxílio à Pesquisa - Temático