Pre-breeding and Population Improvement

Pre-breeding refers to all activities designed to identify desirable characteristics and/or genes from unadapted (exotic or semi-exotic) materials, including those that, although adapted, have been subjected to any kind of selection for improvement. It is an essential part of germplasm diversification strategies. Pre-breeding is the most promising alternative to link genetic resources and breeding programmes. As pre-breeding is being carried out, the resulting materials are expected to have merit to be included in ordinary breeding programmes. There are at least three distinct uses of genetic enhancement. The first is to prevent genetic uniformity and consequent genetic vulnerability. Only recently has pre-breeding-genetic enhancement-become a necessary, frequent and planned part of all plant breeding activities, an essential part of germplasm diversification strategies. Genetic enhancement has a second important purpose that of raising yield levels to new heights. This goal is more often hoped for than achieved, but it is true that most breakthrough cultivars have highly diverse parentage. The semi-dwarf wheat, the high yield dwarf rice, the first US hybrid sorghums and even the first US Corn Belt dent maize cultivars are examples. In each case, extensive pre-breeding preceded development of the breakthrough, high-yield cultivars. The pre-breeding was used to adapt diverse kinds of germplasm to new genetic backgrounds and new geographic locales. Genetic enhancement is used to bring in new quality traits not found in local cultivars. New levels of protein percentage in wheat or unusual starch properties in maize are examples.