Abstract:
Carrot (Daucus carota L.) is one of the most widely grown and eaten vegetable but it is more
vulnerable to many postharvest diseases such as black rot, which is caused by the fungus Alternaria
radicina. Since there are many disadvantages of using fungicides,it is important to find an effective
biocontrol method to control A. radicina. In the present study, the use of fungus Trichoderma
asperellum in controlling A. radicina was investigated. Pure cultures of A. radicina which were
isolated from infected carrot taproots were tested against T. asperellum using the dual culture
technique. As the control A. radicina pure culture was used without T. asperellum. The A. radicina
radial growth reduction percentage was found to be 58.33% . Then the effect of Trichoderma spp. in
control of black rot was studied by making a small wound in healthy, organic, disinfected carrots and
inoculated them with 1 mL of A. radicina conidial suspension. A 1 mL of T. asperellum (2.46×1010
spores per 1 mL) was added to the wounds after 48 hours. Positive control was the fungicide,
Mancozeb and the negative control was sterilized distilled water. After 10 days of incubation at room
temperature, T. asperellum reduced A. radicina by 72.63%. which is approximately similar to the
effect of the positive control. T. asperellum had significantly (p<0.05) decreased disease occurrence
and severity. In addition, inoculation of T. asperellum had greatly improved the minimum keeping
time of average 13 days without characteristics symptoms which is seven days higher than the
negative control. It can be conclude that, biological control of postharvest diseases by T. asperellum
is an alternative to the use of fungicides and it could be a good solution for black rot disease in
carrots.
Keywords: Carrots; Biocontrol; Trichoderma asperellum; Black rot; Alternaria radicina
