CROP IMPROVEMENT THROUGH TISSUE-CULTURE

Plant tissue culture comprises a set of in vitro techniques, methods a nd strategies that are part of the group of technologies called plant biotechnology. Tissue culture has been exploited to create genetic var iability from which crop plants can be improved, to improve the state of health of the planted material and to increase the number of desira ble germplasms available to the plant breeder. Tissue-culture protocol s are available for most crop species, although continued optimization is still required for many crops, especially cereals and woody plants . Tissue-culture techniques, in combination with molecular techniques, have been successfully used to incorporate specific traits through ge ne transfer, In vitro techniques for the culture of protoplasts, anthe rs, microspores, ovules and embryos have been used to create new genet ic variation in the breeding lines, often via haploid production. Cell culture has also produced somaclonal and gametoclonal variants with c rop-improvement potential. The culture of single cells and meristems c an be effectively used to eradicate pathogens from planting material a nd thereby dramatically improve the yield of established cultivars. La rge-scale micropropagation laboratories are providing millions of plan ts for the commercial ornamental market and the agricultural, clonally -propagated crop market. With selected laboratory material typically t aking one or two decades to reach the commercial market through plant breeding, this technology can be expected to have an ever increasing i mpact on crop improvement as we approach the new millenium.