Alien Gene Transfer: Challenges and Opportunities

Abstract

Alien genes have contributed several traits in the crop plants which are not available in the cultivated background. These have helped plant breeders in creating newer genetic diversity, thereby providing additional avenues of selection of better plant types. Vertical and horizontal transfer of alien genes has changed the fate of several crops by imparting resistance to diseases and insect–pests, tolerance to abiotic stresses such as salinity, water stress, and high temperature as well as improving quality. However, alien gene transfer is always not so easy and smooth as it appears from the successful examples of such transfers with massive effects in some crops, especially cereals. Several challenges such as pre- and post-fertilization barriers in distant crosses, problems in normal chromosome pairing, linkage drag, pleiotropic effects and role of recipient genome background on the expression of introgressed alien gene(s) in HGT and erratic regeneration protocols, difficulty in isolation of genes from wild species and their expression in recipient plants, and possibilities of gene flow from cultivated to wild types pose significant challenges to make alien gene transfer a routine process across all crop species. Nevertheless, refinements in various gene transfer technologies have led to generation of tremendous opportunities which provide newer means to obtain successful alien gene transfer in even those species which were earlier considered to be either recalcitrant to tissue culture or were considered as difficult. This chapter discusses in detail various challenges and opportunities associated with alien gene transfer in crop plants.