Abstract
Postbloom fruit drop (PFD), an important disease caused by Colletotrichum spp., affects citrus yields in Brazil. PFD is characterised by the presence of necrotic lesions on the petals and stigmas of citrus flowers and by the subsequent abscission of young fruit. PFD epidemics have high disease progress rates, which is unusual for a pathogen that produces acervuli and is dispersed by rain. It is possible that other dispersal agents, such as insects and pollen, are involved in the spread of this disease. The objective of this work was to test whether citrus pollen grains can be colonised by Colletotrichum acutatum. Studies using light and electron microscopy showed that the pollen of Citrus sinensis can be infected by C. acutatum. This pathogen can penetrate and colonise citrus pollen grains 24 h after inoculation with the pathogen. The germ tube of conidia either penetrates the pollen sporodermis directly or passes through pollen germ pores. A single hypha can colonise more than one pollen grain. On the surface of the stigma, conidium formation can be observed. This study shows that Citrus sinensis pollen may, in fact, play a role in the spread of C. acutatum in citrus orchards.
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Acknowledgments
This project was supported by FAPESP (São Paulo Council for Research) (Proc: 2008/54176-4; 2009/00425-6) and Fundo de Defesa da Citricultura, FUNDECITRUS, Araraquara, SP, Brazil.
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Marques, J.P.R., Amorim, L., Spósito, M.B. et al. Infection of citrus pollen grains by Colletotrichum acutatum . Eur J Plant Pathol 136, 35–40 (2013). https://doi.org/10.1007/s10658-012-0078-2
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DOI: https://doi.org/10.1007/s10658-012-0078-2