Abstract:
Red rot disease, caused by the fungal pathogen Colletotrichum falcatum Went. (Also,
known as Glomerella tucumanensis), poses a significant threat to global sugarcane
(Saccharum officinarum L.) cultivation. The conventional use of chemical fungicides
has been limited due to pathogen resistance and environmental concerns. This study
aimed to assess the efficacy of six medicinal plant extracts, namely Azadirachta indica
(Neem), Solanum torvum (Turkey Berry), Zingiber officinale (Ginger), Persea
americana (Avocado), Curcuma longa (Turmeric), and Psidium guajava (Guava), for
managing red rot disease in sugarcane. Agar well method was used to evaluate the
antifungal properties of the selected plant extracts against C. falcatum. Concentration
gradient started from 100mg/ml to 225mg/ml of the plant extracts were tested to
determine their inhibitory effects on fungal growth and mycelial development. All data,
collected from agar well method, were rigorously analysed at a 5% confidence level
using Minitab 17.0 statistical software. The choice of a 5% confidence level was based
on established statistical practices to ensure robust results. This study observed the
initiation of fungal growth characterized by the development of white mycelia.
Subsequently, the formation of white cottony aerial mycelia ensued, undergoing a
transformation into a light, loose, and floccose texture within a period of five to seven
days. The colony's coloration transitions were to either white or grey during this period.
Conidia produced by the fungus exhibit a diverse range of shapes, including elongated,
fusiform, curved, and straight forms as their common shape. The preliminary
phytochemical analysis of six plant extracts exposed varying profiles of availability of
bioactive compounds. Notably, A. indica and S. torvum leaf extracts exhibited the
presence alkaloid, flavonoids, tannin, and saponin, while absence of steroids. Future
studies should delve into the specific mechanisms underlying the impact of alkaloid,
flavonoids, tannin, and saponin on the pathogen, considering factors such as
concentration, interaction dynamics, and potential synergistic effects. In general
conclusion, suggests that the plant extracts have distinct effects on the zone of
inhibition (ZOI). P. guajava leaves extract showed the highest ZOI (22.83mm) against
the C. falcatum at the minimum inhibition concentration (MIC) 200mg/ml. Both Z.
officinale and A. indica exhibited similar effects on C. falcatum, with recorded
measurements of 16.68 mm and 16.66 mm, respectively. This finding highlighted the
potential use of plant extracts on C. falcatum as an environment friendly and
sustainable alternative for the management of red rot disease in sugarcane cultivation.
