CHARACTERIZATION AND DELINEATION OF AGRO-ECOLOGICAL ZONES AND EVALUATION OF CROP GENOTYPES

Abstract

Success of a crop breeding programme depends on the efficiency of evaluation of the available genotypes and identifying high yielding types adapted to a given environment and management conditions. Crop growing environments in tropics and subtropics are highly diverse and complex due to the effect of abiotic and biotic factors and the varying crop management systems. For such environmental complexities it is almost impossible to define the environment under which varieties should be selected. A reasonable compromise is to test the materials over;a sample of a wide range of the conditions in the target growing environment. Identification of broad agroecological regions (zones) and common and uncommon features between the test sites within a region allows the determination of an optimum regional and national testing programme. The paper discusses the importance of G x E interactions caused by weather, edaphic and biological factors in an apparently homogeneous geoclimatic subdivision analysis of abiotic and biotic factors, but also the cultivar response to environment for improving the efficiency of a testing network. Recent developments in the analytical techniques for delineating environments and their relevance to the national testing network in the developing countries are indicated.