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 effi cacy 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 effi cacy 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 specifi c objectives of the breeding program, they cannot replace sexual hybridization for gene transfer. It is important for the plant breeders to refi ne and exploit fully some of the underexploited techniques described in this review in raising wide sexual hybrids.

Introgressiomics: a new approach for using crop wild relatives in breeding for adaptation to climate change

“…When pre-zygotic and post-zygotic barriers cannot be overcome to obtain hybrid plants, the use of bridge species has to be considered (Shivanna and Bahadur, 2015). These species are compatible with one or both target taxa for interspecific hybridization.…”

“…This applies also to other plants from subsequent backcross generations. One way to recover fertility of the hybrid is duplicating its genome (Khush and Brar, 1992;Rieseberg and Carney, 1998;Shivanna and Bahadur, 2015). In this way normal chromosome pairing can be restored, although the hybrid plant will be polyploid, which may be an obstacle for obtaining subsequent generations due to different ploidy levels.…”

Capsicum: Breeding Prospects and Perspectives for Higher Productivity

“…This was the first successful attempt at embryo rescue in the Capsicum genus. It is yet another example of extensive hybridization in which immature interspecific embryos or embryos from different species were/were rescued prior to abortion, as was the case with the hybridization of C. annuum and C. baccatum [39].…”

Development and use of introgression populations for the detection of QTL related to important agronomic traits in eggplant

“…Several techniques allow to overcome these barriers, such as stigma treatment and pollen mixture with compatible pollen for pre-zygotic, and embryo rescue and in vitro culture for post-zygotic . When prezygotic and post-zygotic barriers cannot be overcome, the use of bridge cross method have demonstrated to be very effective in obtaining hybrid plants (Shivanna and Bahadur, 2015).…”

“…In the case of hybrids with partial sterility, their use as female parent can increase the success rate of fertilization, allowing to obtain viable progeny . Another strategy is the duplication of the hybrid genome, which sometimes leads to the restoration of pollen fertility (Shivanna and Bahadur, 2015). This approach involves some additional steps, since the resulting hybrid is a tetraploid and, therefore, its ploidy may not coincide with that of the recurrent parent (the cultivated species).…”