Histopathology of postbloom fruit drop caused by Colletotrichum acutatum in citrus flowers

Author(s)

Rodrigues Marques, Joao Paulo ^[1] ; Amorim, Lilian ^[1] ; Sposito, Marcel Bellato ^[1] ; Appezzato-da-Gloria, Beatriz ^[1]

Affiliation

^[1] Univ Sao Paulo, Escola Super Agr Luiz de Queiroz, BR-13418900 Sao Paulo - Brazil

• Document type: Journal article
• Source: European Journal of Plant Pathology; v. 135, n. 4, p. 783-790, APR 2013.
• Web of Science Citations: 12

Abstract

Postbloom fruit drop (PFD) is caused by both Colletotrichum acutatum and C. gloeosporioides and is a potentially serious disease in citrus that occurs when flowering coincides with rainfall. The fungus incites necrotic lesions in petals and stigmas leading to premature fruit drop and reduced yield. The mechanisms of infection and survival of the causal agents remain to be fully elucidated. In the present study, we investigated the histopathology of PFD caused by C. acutatum in the petals and stigmas of sweet oranges using electron and light microscopy. In the petals, pathogen penetration occurred intra and intercellularly and also through the stomata, with intercellular penetration occurring most frequently. The distinct tissues of the petals were colonised, including the vascular system, particularly the xylem. Acervuli were observed on both sides of the petals. Although the fungus did not penetrate through the epidermal cells of the stigma, C. acutatum caused necrosis and an increase of phenolics in this tissue. A protective layer rich in lipophilic and phenolic compounds was formed under the necrotic area and crystals of oxalate were associated with the sites where the pathogen was present. (AU)

• FAPESP's process: 09/00425-6 - Postbloom fruit drop of citrus: histopathology of Colletotrichum acutatum
• Grantee: João Paulo Rodrigues Marques
• Support Opportunities: Scholarships in Brazil - Doctorate