Asian Journal of Microbiology, Biotechnology & Environmental Sciences Paper

Vol 10, Issue 4, 2008; Page No.(725-731 )

ANTIFUNGAL EFFECTS OF SOLVENT EXTRACTS OF NEEM LEAVES ON SEED PATHOGENS OF GROUNDNUT

E. C. WOKOMA AND C. NWAEJIKE

Abstract

The blotter method was used to assay soybean, groundnut and cowpea seeds for germination and fungal infection levels. Soybean significantly (p=0.05) had the best germination (86%), followed by groundnut (50%) and cowpea (8%) while groundnut had the highest infection level (91%) followed by cowpea (32%) and soybean (9%). Assay of four groundnut seed lots indicated that germination and infection levels ranged from 60% to 80% and 67% to 91%, respectively. Fungi isolated from the four seed lots were Fusarium moniliforme, Rhizopus stolonifer, Pcnicillium digitatum, P. oxalicum, Aspergillus flavus and A. niger. Potato dextrose agar (PDA) amended with different concentrations of chloroform extracts of Azadirachta indica leaves was used to evaluate the efficacy of A. indica in controlling F. moniltforme isolated from groundnut seeds. Linear growth, mycelium dry weight and sporulation of F. moniliforme was significantly reduced with increasing concentrations of the extracts. The effects of seed treatments using two brands of Na0C1 and A. indica extracts, on in vitro germination and infection level of the seeds was also evaluated after 4 days of incubation. Seed treatment with imported Na0C1 or A. indica did not reduce germination below the expected range of 60% to 80%, earlier detected in naturally infected seed lots. l5 solution of imported Na0C1 reduced infection by 34% while 10 mL methanol and chloroform extracts per 200 seeds reduced infection by 31.5% and 37%, respectively. Therefore, A. indica leaf extracts may be acceptable substitutes for treating groundnut seeds before planting.

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