Abstract:
Chemical control using synthetic chemical fungicides is still the most common
method of controlling postharvest diseases of fruits. Plant extracts which are rich in
antimicrobial secondary metabolites such as terpinoids, alkaloids, saponins and
flavonoids could be possible alternatives for synthetic fungicides. Current study was
focused on evaluating the antifungal effect of ethanolic extract of Croton aromaticus
(Kappettiya) leaves in vitro against mycelial growth and the spore germination of
postharvest fungal pathogens isolated from fruits of banana (Colletotrichum musae,
Rhizopus sp., Lasiodiplodia theobromae) papaya (Rhizopus stolonifer,
Colletotrichum gleosporioides, Lasiodiplodia theobromae) and mango (Alternaria
alternata, Pestalotiopsis mangiferae, Lasiodiplodia theobromae). Surface sterilized
diseased banana, papaya and mango fruit tissues were cultured on PDA plates in
order to obtain pure cultures of possible fungi and they were identified by
morphological and microscopic characteristics, using identification keys. Inhibitory
effect of the ethanolic extract of C. aromaticus against test pathogens were
investigated by well diffusion method using PDA medium, by incorporating crude
extract dissolved in DMSO, ranging from 1 mg/ml up to 300 mg/ml concentrations
along with the positive (Captan) and negative (DMSO) controls. Significant (P <
0.05) inhibitory effects were exhibited by the ethanolic extract of C. aromaticus
leaves against all test pathogens except L. theobromae. The highest mycelial growth
and spore germination inhibition of most of the pathogens were observed at 100
mg/ml. The lowest Minimum Inhibitory Concentration of the leaf extract (5 mg/ml)
was observed for spore germination inhibition of C. gleosporioides and P.
mangiferae. TLC analysis revealed four compounds having Rf values of 0.551,
0.672, 0.810 and 0.913. Phytochemical screening of ethanolic extract revealed the
presence of alkaloids, terpenoids, quinones, phytosterols and flavonoids. Current
findings indicate the potential use of ethanolic extract of C. aromaticus leaves in
controlling banana, papaya and mango postharvest fungal pathogens in vitro.
