Efficacy of Biotechnological Approaches to Raise Wide Sexual Hybrids

Abstract

Present-day cultivars of crop species have become susceptible to a range of biotic and abiotic stresses because of their narrow genetic base. The genes imparting resistance to these stresses are no more available within the cultivated species but are present in many wild and weedy relatives. To transfer desirable genes to the cultivars, the production of wide hybrids is an important pre-breeding requirement. One of the major limitations of wide hybridization is the presence of strong crossability barriers that operate before as well as after fertilization. During the last several decades, many biotechnological methods have become available, and their integration into the traditional methods of wide hybridization greatly increases the efficacy and reduces the time and efforts needed. Some of these include pollen storage, application of growth substances, stump pollination, placental pollination, in vitro fertilization and embryo rescue in the form of ovary, ovule and embryo culture. This review highlights the efficacy of these techniques in realizing wide hybrids and emphasizes the use of combination of techniques to make these approaches more successful. The interest on production and use of sexual wide hybrids has greatly reduced after the development of the techniques of somatic hybridization and genetic transformation. Although they provide powerful technologies to achieve some specific objectives of the breeding program, they cannot replace sexual hybridization for gene transfer. It is important for the plant breeders to refine and exploit fully some of the underexploited techniques described in this review in raising wide sexual hybrids.