ABSTRACT
For thousands of years prior to the discovery and proliferation of modern plant breeding techniques, rice farmers throughout the world utilized locally adaptable traditional varieties (TVs) in the reproduction of agriculture. These varieties are still used throughout the developing world—usually in marginal rice farming environments where modern varieties (MVs) are either unsuitable or unavailable. These genetically heterogeneous varieties or ‘landraces’ formed the foundation of traditional rice farming systems and provided farmers with the means to adapt to variable environmental stresses and economic pressures. With the advent of modern plant breeding techniques and through large scale interventions such as the Green Revolution, these relatively adaptable but often low yielding varieties were gradually replaced with higher yielding and photoperiod insensitive MVs—particularly in favourable rice growing environments. While this process has no doubt helped increase agricultural production at aggregate levels worldwide it has also, according to some authors, led to widespread genetic erosion as genetically heterogeneous TVs are substituted for more genetically homogenous MVs (Thrupp, 2000).
