Role of Chitosan Extracted from Shrimp Waste in Controlling Tomato Blackmold Disease Caused by Alternaria alternata

Tomato suffers from several diseases at all stages of its life. Blackmold, caused by Alternaria alternate (Fr.)
Keissler is one of the most important postharvest disease of tomato. The effect of various concentrations of chitosan
solution on A. alternata the causal agent of blackmold disease of tomato fruits on mycelial growth was studied. The
isolate was tested in vitro using PDA amended with seven concentrations of chitosan (0, 1, 2, 3, 4, 5 and 6 mg ml–).
Chitosan significantly (P < 0.05) inhibited the radial mycelial growth of this fungus by 67.4% at 6 mg ml1
concentration. Tomato fruits treated with aqueous solution of chitosan compared with the Ipromise® fungicide
(Thiophonate-methyl 20% + Iprodione 20%) was artificially inoculated with A. alternata and incubated at 8, 18 and
28°C. Lesion diameters and total phenolic contents were recorded 7 and 14-days after inoculation. Chitosan also,
significantly (P < 0.05) reduced the lesion diameters of tomato fruits which were smaller for all treatments when stored
at 8°C compared to the control treatment. Chitosan treatment resulted in the highest increase in total phenolic contents
over the untreated control. Whereas a less increase in total phenolic contents was recognized in fungicide treatment. In
all treatments, total phenolic contents increased first and declined at the end of storage. The results of this study indicate
that chitosan was a alternative safe coating method especially when stored at low temperature degree for prevents
tomato fruits blackmold disease which causes economic losses during transportation, marketing and storage.