Abstract
ABSTRACT: One of the major problems in the commercialization of avocados is the incidence of postharvest diseases, especially anthracnose (Colletotrichum spp.) and stem-end rot (Lasiodiplodia theobromae, Fusicoccum aesculi and Neofusicoccum spp.). As there is a lack of epidemiological information on these pathosystems, the objective of this study was to establish a method to detect quiescent infections and characterize their temporal progression and spatial pattern in a commercial orchard. Detection of quiescent infections was evaluated in flowers and fruits that were immature and in commercial harvest stage, treated with paraquat, ethrel or water. Treatment of flowers and immature fruits with paraquat led to rapid detection of Colletotrichum spp. In two seasons of a ‘Hass’ avocado orchard, the incidence of diseases was evaluated from open flowers to fruit harvest, totaling 11 evaluations at biweekly intervals. When fruits reached the harvest stage, the spatial distribution of diseased fruits in the trees was evaluated by means of dispersion index and modified Taylor’s law. Considering the evaluation of temporal disease progression, anthracnose was the most important disease, presenting a high initial incidence of 60 and 86% diseased flowers in the two seasons, respectively, while fruits showed an average disease incidence of 70 and 87%, respectively. Stem-end rot was observed only in fruits since the beginning of their development and presented low incidence (<8% fruits), significantly inferior to that of anthracnose. The diseases showed random dispersion within the trees, indicating that their initial inoculum is evenly distributed in the plants.
Highlights
The avocado (Persea Americana Mill.), which belongs to the family Lauraceae, is a fruiting tree that adapts very well to the subtropical climate in Brazil
Anthracnose and stem-end rots are defined as quiescent diseases since the infection occurs during fruit development but symptoms only appear during ripening, which is due to the physiological conditions imposed by this host
Each flower and fruit was washed in running water for 3 minutes and individually placed on plastic trays, which were stored under continuous light, at 25 °C and 80-85% relative humidity (RH), in an incubation chamber
Summary
The avocado (Persea Americana Mill.), which belongs to the family Lauraceae, is a fruiting tree that adapts very well to the subtropical climate in Brazil. Anthracnose and stem-end rots are defined as quiescent diseases since the infection occurs during fruit development but symptoms only appear during ripening, which is due to the physiological conditions imposed by this host. V.49, n.8, healthy at harvest but can manifest symptoms of these diseases during storage and commercialization. Temporary fungal growth inhibition may occur in any stage of the process, from spore germination to colonization (PRUSKY, 1996). The magnitude of quiescent infections in the orchard should be learnt, but early detection of quiescent pathogens depends on techniques that modify the fruit physiology, allowing the expression of symptoms. Ethylene promotes fruit ripening, leading to biochemical and physiological changes necessary for the fungus to pass through the quiescence stage and colonize the fruit. Paraquat in turn induces lipid peroxidation and membrane integrity loss (DODGE, 1971), leading to fruit senescence and expression of disease symptoms
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
