Efficacy of n-hexane plant extracts in the control of rice blast disease

• B.O Adeosun

  Department of Crop, Soil and Pest Management, The Federal University of Technology, PMB 704 Akure, Ondo state, Nigeria.

  Author

• O.R Onasanya

  Department of Agriculture, Federal College of Agriculture, PMB 5029 Moor plantation, Ibadan, Oyo state Nigeria.

  Author

Studies were carried out to determine antifungal attributes of n-hexane extracts of six plant species (Leaves of African Basil; Ocimum gratissimum, Siam weed; Chromolaena odorata, Lemmon grass; Cymbopogon citratus, seeds of Clove; Eugenia aromatica, West African black pepper; Piper guineense, and nuts of bitter kola; Garcinia kola) on Pyricularia oryzae, the incitant of rice blast disease. Plant parts were separately air-dried and ground. Active ingredients were extracted with the aid of n-hexane, using soxhlet apparatus. Antifungal activity of extracts were evaluated in different concentrations (10, 20, 30, 40, 50 and 100%) of plant extracts and carbendazim at 0.5 mg. ml-2 a standard chemical, using the poisoned food technique. Mycelial growth was determined after 7 days of inoculation and incubation at each concentration and control. All plant extracts reduced the growth of Pyricularia oryzae at all tested concentrations. Highest growth inhibition was achieved at 100 % concentration with E. aromatica, 100%; P. guineense 98% and G. kola, 97.3% growth inhibition, hence Cybopogon citratus, Chromolaena odorata, Ocimum gratissimum and lower concentrations (10-50%) were discarded from the study. Only the extracts from E. aromatica, G. kola and P. guineense at 100% concentration were used subsequently. Leaf blast was evaluated on Nerica and Faro-44 varieties. The rice seeds were inoculated with spores of pure culture of P. oryzae and treated with 100% extracts concentration of E. aromatica, P. guineense and G. kola each being the most promising botanicals among the six evaluated ones from the in vitro study. The untreated seeds stood as control while seeds treated with Carbendazim at 0.5 mg.ml-2 stood as negative control. Extracts from P. guineese and E. aromatica reduced leaf blast incidence by 45.8% and 37.5% respectively. Subsequently, rice seeds could be treated with 100% n-hexane extract concentration of P. guineense and E. aomatica against the growth and development of Pyricularia oryzae with a resultant control of rice blast disease.

1. B.O Adeosun, Department of Crop, Soil and Pest Management, The Federal University of Technology, PMB 704 Akure, Ondo state, Nigeria.

   Department of Crop, Soil and Pest Management, The Federal University of Technology, PMB 704 Akure, Ondo state, Nigeria.

2. O.R Onasanya, Department of Agriculture, Federal College of Agriculture, PMB 5029 Moor plantation, Ibadan, Oyo state Nigeria.

   Department of Agriculture, Federal College of Agriculture, PMB 5029 Moor plantation, Ibadan, Oyo state Nigeria.

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