Journal of Agricultural Biotechnology and Sustainable Development 2141-2340 Academic Journals 10.5897/JABSD.9000012 C. Parwada C. T. Gadzirayi A. B. Sithole * E-mail: crparwada@yahoo.com 2011 30 04 2011 15 02 2011 3 4 72 76 This is an open-access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from https://academicjournals.org/journal/JABSD/article-abstract/945298D1643 The full text article is available as a PDF file from https://academicjournals.org/journal/JABSD/article-full-text-pdf/945298D1643