ABSTRACT
Improvement in any crop involves crossing among the different varieties or genotypes to create variability, followed by selecting the desirable genotype to be released as a variety. Genetic variation has been eroded in most of the crops under modern agriculture systems. The processes leading to postzygotic barriers in distant hybridizations are poorly known. The prevailing view is that postzygotic isolation is usually attributed to the negative epistatic interactions of parental genomes in artificially produced interspecific hybrids. Hybrid sterility and hybrid breakdown are commonly encountered during wide hybridization studies. Hybrid breakdown is a difficult problem to solve because of its complex mode of inheritance. When species with different ploidy levels are crossed, hybridization between them is relatively difficult than when both species with the same ploidy level are crossed. Interspecific hybridization can be easily forced in the family of Brassicaceae , whereas under natural conditions, the gene flow is very limited.
