FUNGITOXICITY OF ASHES FROM SOME TROPICAL TREES AGAINST SEEDBORNE FUNGI ISOLATED FROM SUNFLOWER (Helianthus annuus L.)

Abstract

The ashes of sixteen tropical trees were evaluated in vitro for their potential to reduce the mycelial growth of seedborne fungi; Aspergillus niger, Fusarium oxysporum and Fusarium incarnatum. Sawdust samples of sixteen tropical trees were collected from the saw mill industries and were sun-dried and burnt using a pre-fabricated incinerator (12 – 100kg/hr) to get ash. The ash samples were heat sterilized (Gallenkamp hot air oven, 160°C for 5 h) to eliminate the resident mycobiota. Fungi tested were isolated from sunflower seeds via blotter test or agar plate methods and inoculated on Petri dishes containing Potato dextrose agar media amended with ash while un-amended media plates served as control. Inoculated media were incubated under room temperature at 28 ± 1 °C. Diameter of the fungal colony was measured using a meter rule along two diagonal lines drawn perpendicularly on the reverse side of each Petri dish 7th day after inoculation. Fiscus exasperata ash reduced mycelial growth of fungi by an average of 96.93%. Average mycelial growth reduction by Gmelina arborea and Terminalia superb ashes were 87.65% and 84.74% respectively. These were followed by Piptadeniastrum africanum and Sterculia rhinopetela ashes with 78.37 and 76.32% mycelial growth reductions respectively. Bombax spp. ash had the least fungitoxicity effect as evidenced by only 25.69% in mycelial growth reduction of F. incarnatum. This study showed that the prospect of wood ash in the control of seedborne pathogens and a possible alternative to chemical pesticides