Siti Juhana Tukiman, Jalilah Rapie, Zubaidah Suhardi, Nurbazlaa Nawi, and Hideyuki Nagao

pp. 1 - 11

Abstract

Dry rot of pumpkins caused by F. solani f. sp. cucurbitae race 2 is a well known post harvest disease. In Malaysia,
crust-like lesions are often observed on the surface of pumpkins in local markets. These symptoms look like the scab caused
by Cladosporium cucumerinum or the Fusarium rot caused by Fusarium spp. Most of the symptomatic crusts did not soften
or develop further in our observations. As these crusts are merely considered as the mechanical injuries in the local markets,
they do not reduce their marketability of pumpkin. However, F. solani was frequently isolated from these symptoms in our
preliminary study. Thus these crust symptoms were distinguished from the scab, the Fusarium rot, the preharvest dry, hard
rot (type 1) and the dry rot caused by other Fusarium spp. as reported previously. Histological observation of naturally
occurring raised pimples or crust symptoms showed periderm formation that apparently healed the loss of palisade layer.
Therefore, hereafter, the term ‘canker’ is used to explain the crust symptoms and ‘scab’ for the raised pimples. A majority of
the fungal isolates from the canker was identified as F. solani (41.6%). The pathogenicity test with 12 isolates of F. solani on
mature pumpkins did not efficiently reproduce canker. The wound on immature fruit, 1 to 5 weeks-old, successfully produced
canker regardless of the inoculum, while the unwounded part did not show any symptom with inoculation. Canker symptom
of pumpkin is considered like the fruit defense mechanisms after mechanical injury.