the effectiveness of natamycin against carrot mold post-harvest

1. THE EFFECTIVENESS OF NATAMYCIN
AGAINST CARROT MOLD POST-
HARVEST
As stated previously in this section, research on new
applications for Natamycin in the food industry is
constantly being carried out all over the world.
We have also covered its successful application in the
maintenance of the post-harvest quality of plants such as
red fruits, and now we discuss a study on one of the most
widely consumed succulent root vegetables in the world:
carrots.
The study summarised here was carried out by Chinese researchers for the Brazilian
Phytopathology Society, and recently published in the journal Tropical Plant Pathology.
The study examined the inhibitory effect of Natamycin on the fungus Sclerotinia Sclerotiorum,
the pathogen causing white mold in carrots post-harvest.
In this case, the fungus does not attack carrots in storage after they have been harvested, but
lies dormant in the soil. It can survive for up to ten years in the ground.
The study demonstrated that Natamycin is an important anti-fungal agent against S.
sclerotiorum both in vitro and in vivo.
In order to study the effect of natamycin under conditions as close as possible to real ones (in
vivo), fresh carrots in perfect condition were submerged in increasing concentrations of
Natamycin (50, 100, 150 and 200 mg of L-1) and then air dried for 2.5 hours. A sample of the
pathogen was then placed on top of these carrots.
The severity of the infection was evaluated six days after the carrots had been inoculated, by
measuring the length of the lesion created by the fungus on the root.

2. The image below shows the results of the tests carried out in vitro (a/b and c/d) and in vivo
(e/f).
Source: Tropical Plant Pathology. 3 June 2020.
Samples b and d are the control sample without any Natamycin, while a and c contain a
concentration of Natamycin of 1.5 mg l-1. The a/b pair is the samples after 5 days (there is no
linear growth of the fungus in a, while there is in b), and the c/d pair is the same samples after
15 days of culture in vitro (the blackish structures of the fungus do not grow in c as they do in
d).
In vivo tests showed that the concentration of inoculated Natamycin should be at least 50 mg
l-1 if it is to be effective against white mold in carrots. In the e/f pair, sample e contains
natamycin and it appears to be protected after 6 days, while sample f presents a generalised
infection from the centre to the ends over the same period of time.
Although previous studies had highlighted substances such as chitosan, silicon and UVC
radiation as potential means to reduce infection by white mold, this more recent study
suggests that Natamycin is another tool that can be used in countries where its use is
authorised in order to prevent the loss of more than 50% of the harvest due to white mold
under storage conditions that favour the fungus.
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