BSc-MSc (Integrated)

Elephant foot yam (Amorphophallus paeoniifolius (Dennst.) Nicolson) is
an important tuber crop popular as a food security crop and as a remunerative
cash crop. A. paeoniifolius is susceptible to number of diseases and the incidence
of post-harvest rot in EFY is very high at all stages from harvesting to
consumption, leading to reduction in the quality and quantity of stored planting
material. The recommended management practices are unable to reduce the
disease incidence satisfactorily and suggest the involvement of more pathogens
to the loss. The present study, “Molecular characterization of pathogens
associated with post-harvest diseases in elephant foot yam” was conducted at the
Division of Crop Protection, ICAR- Central Tuber Crops Research Institute
(CTCRI), Sreekariyam, Thiruvananthapuram during October 2017 – August
2018 with an aim to identify the pathogens responsible for post-harvest diseases in elephant foot yam by establishing
pathogenicity and molecular characterization.
Sixty-two samples showing tuber rot symptoms were collected; detailed symptoms were studied and grouped the symptoms into nine categories.
Ninetyone isolates were obtained from the samples and the duplicates of isolates
were avoided by studying colony morphology, growth rate, and spore production
etc of the isolates. Thirty-three isolates were selected for pathogenicity test and
Koch’s postulates were proved with fifteen isolates. The morphology as well as
symptom expression in host by both original and reisolated isolates were
compared and found same. While studying the symptom, 86.6% of pathogens
produced discoloration, 73.3% shown rotting and softening was induced by
33.3% pathogens.
Morphological and cultural characteristics of the isolates were studied and
the pathogens were tentatively identified. The précised identification of the
pathogens was done by amplifying the rDNA ITS region using ITS1 and ITS 4
primers. The pathogens were identified as Athelia rolfsii, Lasiodiplodia
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theobromae, Rhizopus oryzae, Cunninghamella elegans, Rhizoctonia solani,
Ceratobasidium sp., Fusarium brachygibbosum, Fusarium solani, Fusarium
oxysporum, Colletotrichum gloeosporioides, Aspergillus tamarii, Aspergillus
nomius, Aspergillus niger and Penicillium citrinum.
The study identified eight new organisms associated with tuber rot in
elephant foot yam. Most of the newly identified organisms are reported to cause
post-harvest rot in other tuber crops. Athelia rolfsii and Lasiodiplodia
theobromae were found to cause maximum damage. Fusarium solani and
Aspergillus niger caused more damage to the tubers during combined infection.
Initial infection with Athelia rolfsii can accelerate the infectivity of Lasiodiplodia
theobromae and Fusarium brachygibbosum.
The present study helped in precisely identifying the pathogens responsible
for postharvest diseases in elephant foot yam. This knowledge can be used for
developing appropriate strategy to mitigate postharvest diseases in elephant foot
yam.