The use of haploid systems in plant genetic manipulation
In the present study the use of haploid plants and tissues was considered in relation to plant genetic manipulation. Haploid plants can be exploited directly, in the synthesis of true breeding lines. Alternatively, haploid plants and tissues may provide material for further experimentation involving protoplast fusion. Both approaches were investigated. Cyclamen persicum an attractive flowering plant is grown commercially from seed produced following open cross-pollination. As a result, Cyclamen is highly heterozygous, but the resulting variation is commercially undesirable. Inbreeding depression prevents the recovery of commercial inbred lines. Anther culture as an alternative approach for the recovery of true breeding lines was attempted. In order to test the efficiency of the culture procedure and conditions, anther culture of N. tabacum was also attempted, since this species is known to be highly responsive to anther culture. Despite the recovery of very many allodihaploid N. tabacum, plants from anther culture, no success was achieved with Cyclamen, and the possible reasons for this are discussed. It has recently been proposed that limited gene transfer might be achieved by somatic hybridisation if diploid protoplasts of a crop species were fused with haploid protoplasts of a wild type species, and novel allotriploid somatic hybrid plants recovered. Haploid protoplasts can be isolated from anther culture derived plants, however the range of species responsive to anther culture is limited. Tetrads, formed as a result of meiosis in the pollen mother cells, were investigated as an alternative source of haploid protoplasts for fusion studies. Somatic hybrids were recovered following fusion between N. tabacum leaf mesophyll (2n) and N. glutinosa tetrad (n) protoplasts. The somatic hybrids were fertile, and the progeny of the first backcross to N. tabacum were obtained. These results, and potential limitations to somatic hybridisation are considered in the context of plant breeding.