The effects of postharvest treatments and sunlight exposure on the reproductive capability and viability of Phyllosticta citricarpa in citrus black spot fruit lesions
Date
2020-12-21
Journal Title
Journal ISSN
Volume Title
Publisher
MDPI
Abstract
Citrus black spot (CBS) is caused by Phyllosticta citricarpa, which is classified as a quarantine
organism in certain countries whose concerns are that CBS-infected fruit may be a pathway for
introduction of the pathogen. This study evaluated the reproductive capability and viability of
P. citricarpa under simulated conditions in which the whole fruit, peel segments, or citrus pulp with
CBS lesions were discarded. Naturally infected ‘Midknight’ Valencia orange and ‘Eureka’ lemon
fruit, either treated using standard postharvest sanitation, fungicide, and wax coating treatments
or untreated, were placed into cold storage for 5 weeks (oranges at 4 ◦C and lemons at 7 ◦C).
Thereafter, treated and untreated fruit were incubated for a further 2 weeks at conditions conducive
for CBS symptom expression and formation of pycnidia. The ability of pycnidia to secrete viable
pycnidiospores after whole fruit and peel segments or peel pieces from citrus pulp were exposed to
sunlight at warm temperatures (±28 ◦C) and ±75% relative humidity levels was then investigated.
The combination of postharvest treatments and cold storage effectively controlled CBS latent infections
(>83.6% control) and pycnidium formation (<1.4% of lesions formed pycnidia), and the wax coating
completely inhibited pycnidiospore release in fruit and peel segments. Pycnidiospores were secreted
only from lesions on untreated fruit and peel segments and at low levels (4.3–8.6%) from peel
pieces from pulped treated fruit. However, spore release rapidly declined when exposed to sunlight
conditions (1.4% and 0% after 2 and 3 days, respectively). The generally poor reproductive ability
and viability of CBS fruit lesions on harvested fruit, particularly when exposed to sunlight conditions,
supports the conclusion that citrus fruit without leaves is not an epidemiologically significant pathway
for the entry, establishment, and spread of P. citricarpa.
Description
CITATION: Moyo, P. et al. 2020. The effects of postharvest treatments and sunlight exposure on the reproductive capability and viability of Phyllosticta citricarpa in citrus black spot fruit lesions. Plants, 9(12):1813, doi:10.3390/plants9121813.
The original publication is available at https://www.mdpi.com
The original publication is available at https://www.mdpi.com
Keywords
Citrus, Pycnidiospores, Citrus black spot, Citrus -- Postharvest diseases and injuries -- Biological control, Citrus fruits -- Storage -- Diseases and pests, Citrus fruits -- Effect of temperature on
Citation
Moyo, P. et al. 2020. The effects of postharvest treatments and sunlight exposure on the reproductive capability and viability of Phyllosticta citricarpa in citrus black spot fruit lesions. Plants, 9(12):1813, doi:10.3390/plants9121813.