Application of Haploids in Plant Breeding
In Vitro production of haploids can solve some problems in genetic studies since gene action is readily manifested due to a single allelic gene present in chromosome of entire genome.
1. Releasing New Varieties through F1 Double –haploid System:
Haploid breeding technique usually involve only one cycle of meiotic recombination. However, many agronomic traits are polygenically controlled. One cycle of recombination is usually insufficient for the improvement of such quantitative traits since linkage between Polygenes will not release all potential variations available in the cross. To overcome these disadvantages, the Chinese developed a method combining anther culture with sexual hybridization among different genotypes of anther derived plants. The anthers of the hybrid (F1) progeny are excellent breeding material for raising pollen-derived homozygous plants (Double –haploids) in which complementary parental characteristics are combined in one generation.
Double –haploids are also useful in studies related to inheritance of quantitative traits. Using double –haploid technique new varieties have been developed in barley, Brassica, rice, maize , rye, potato, pepper and asparagus.
2. Selection of Mutants Resistance to Diseases:
Mutants with resistance to disease is of prime importance in crop improvement. Haploids provide a relatively easier system for the induction of mutations. Some examples of using anther culture technique in mutant successfully are tobacco mutants resistant to black shank disease and wheat lines resistant to scab. (Fusarium graminearum).
3. Developing Asexual Lines of Tree Perennial Species:
Chinese workers obtained pollen –derived rubber tree taller by sic meters which could then be multiplied by asexual propagation to raise several clones. Another example of pollen –haploids in plant improvement is popular.
4. Transfer of Desired Alien Gene:
Chromosomal instability in haploids makes them potential tools for introduction of alien chromosomes on genes during wider crossing programmes. In rice , developing a resistance to blast requires about 12 years by conventional breeding through back crossing. Through hybridization and anther culture, this can be achieved in two years (Examples: cv . Zhonghua No.8 and 9 released by the institute of crop Breeding and cultivation in china.
5. Establishment of Haploids and Diploid Cell Lines of Pollen Plant:
The anther culture technique was used to establish both haploid and diploid somatic cell lines of pollen plants in wheat and maize. Similarly, a haploid tobacco line resistant to methionine sulfoxomide was selected which turned out to be identical in phenotype and effect to the toxin produced by the pathogen Pseudomonas tabaci.