EVALUATION OF ANTIFUNGAL EFFICACY OF SOME LEAF EXTRACTS OF SOME PLANTS ON RED ROT PATHOGEN (Colletotrichum falcatum) OF SUGARCANE (Saccharum officinarum)

Abstract

Botanical extracts have shown appreciable achievement in controlling plant diseases. This became evident in this study when the potency of leaf extracts from Azadirachta indica, Carica papaya, Lawsonia inermis, Khaya senegalensis and Ziziphus spina- christi were tested on the mycelia growth of Colletotrichum falcatum, the pathogen of red rot disease of sugarcane. The infected sugarcane used for isolation and identification were collected from National Cereal Research Institute (NCRI) Badeggi. And a total of sixty (60) healthy sugarcane setts planted were collected from farmers in Wuya rake along Bida Mokwa road in Niger state. The plant leaf materials used in this study were collected from the mountain area at Egubagi village and were identifield at the herberium in the Department of Plant Biology, Federal University of Technology, Minna. After collection, leaves were sterilised using 0.5% sodium hypochlorite and the extraction was done using soxhlet extraction. Tested leaves were subjected to qualitative phytochemical screaming. The isolation and identification of the fungus was done by cutting the transition zone between the rotten tissue and healthy side into 5mm, sterilised and inoculated into potato dextrose agar (PDA) medium. In vitro antagonistic effects of the plant extracts were done using food poison techniques at 75 %, 50 %, and 25 % concentrations while the controls are 0.5g/l (clot) and 0% (sterile distilled water) concentrations with three replicates each. After the in vitro evaluation, the best three plant extracts that had the highest mycelia inhibition were taken to the field to evaluate their effect on the fungus as it affects the growth parameters (plant girth, plant height, number of nodes and internodes length) on the growing sugarcane plants in the screen house (in vivo). The phytochemical analysis of the extractants revealed the presence of alkaloids, flavonoids, phenols, tannins, saponins terpenoids, steroids anthraquinones and cardiacglycosides. The results of in vitro revealed that the percentage mycelia growth inhibition were 100.0±0.00 (Lawsonia inermis ), 53.00±1.15 (Azadirachta indica ), 78.00±0.00 (Carica papaya), 45.00±1.00 (Ziziphus spina-christi ) and 60.60±0.00 (Khaya senegalensis) while controls were 100.0±0.00 (0.5 g/L) and 0.00±0.00 (sterile distile water) positive and negative respectively. The results obtained from the field were promising at 75 % concentration of plant extracts used for the percentage disease reduction with 6.94 %, 15.28 % and 25.8 % Lawsonia inermis, Carica papaya and Khaya senegalensis were used in that order, while controls had 5.90±0.00 0.5 g/L (clot) 0 % (sterile distile water). The percentage inhibition and reduction in all the treatments used were significantly different (P<0.05). The efficacy of the ethanolic leaf extracts increase with the increase in concentrations, 75% concentrations of all the plant extracts showed the highest level of mycelial growth inhibition (in vitro) and percentage disease reduction (in vivo). Extracts from Ziziphus spina−christi (45.00±1.00 %) had the least effect on the percentage mycelia growth of C. falcatum (in vitro) while Khaya senegalensis had least (25.8−35.09 %) effect than other plants extracts used (in vivo) in suppressing the disease severity on sugarcane plants. The results were promising and the best plant extracts can go a long way in reducing the red rot disease of sugarcane on the field.