Plant Hybridization as an Alternative Technique in Plant Breeding Improvement

For ages, plant breeders have relied on the genetic variability that results from sexually crossing plants within the same species. However, the variability that exists within species populations is inadequate, hence the need to exploit desirable traits of interest in distantly related or even unrelated plants through hybridization techniques. Hybridization can be categorized into two; sexual and somatic. Sexual hybridization, also referred to as wide or distant hybridization involves combining two genomes from different parental taxa through pollination, either naturally or by induction. Somatic hybridization involves the fusion of somatic cells instead of gametes, which highly depends on the ability to obtain viable protoplasts and eventually differentiate them to whole plants in vitro. The impacts of hybrids can either be positive or negative. Among the positive attributes of hybrids that have been exploited is heterosis, which results either from dominance, over-dominance or epistasis. Negative ones include sterility, arrested growth of the pollen tube and embryo abortion. To overcome these problems, chromosome doubling, the use of hormones such as 2, 4-Dichlorophenoxyacetic acid (2, 4-D) and embryo rescue have been employed to overcome sterility, arrested growth of pollen tubes and embryo abortion respectively. After the development of hybrids, different hybrid identification techniques have been used to test them such as the use of molecular and morphological markers, cytogenetic analysis and fluorescent in situ hybridization. The use of hybridization techniques in plant improvement remains a vital tool to cross species barriers and utilization of important attributes in unrelated crop plants which could not have been achieved through conventional techniques of plant breeding.