Effect of Time x Naocl Stringency on Extraction of Grain Mold Complex Fungus from Naturally Weathered Sorghum Seeds Surface.

The purpose of surface sterilization is to destroy or remove non-pathogenic fungi and bacteria on the grain surface without killing pathogenic fungi and other microflora present on pericarp and internal part of kernel tissue. The main objectives of this laboratory experiment were to optimize surface sterilization protocol for fungal genera extraction from the kernel surface (pericarp) and to study the effect of bleach percentage and time of treatment. Seven treatments using sterilized double distilled water (0 % bleach (v/v)) and different bleach (NaOCl) concentrations were used with a time interval of 2.5, 5, 7.5 and 10 min. Contamination of Potato dextrose agar (PDA) plates with non-pathogenic fungi like bread mold Rhizopus, bacteria and yeast were reported. These contaminations decreased with increased in time x NaOCl concentration stringency suggesting that the rate of contamination of PDA plates and time x NaOCl concentration stringency have an inverse relationship. Optimized surface sterilization in the range of 10 to 15 % bleach (v/v) for 10 min resulted no contamination. Treatment of kernels with 10 to 15 % bleach (v/v) for 10 min would be best for fungal genera isolation from the kernel surface. Isolated fungal colonies were classified via sequencing using genus specific primers, revealed that Fusarium and Alternaria are the two major fungal genera isolated from kernel surface and internal tissue.