Haploidy and mutation techniques

Mutation techniques have already proven their potential for generating useful variability for plant breeding (Micke et al.,1990; Sigurbjornsson, 1983). The FAO/IAEA Mutant Varieties Database now lists almost 1800 officially released mutant cultivars in more than 150 plant species (Maluszynski et al.,1991, 1992). Mutant cultivars or mutated genes have significantly contributed to the economy of many countries. One example is X-ray induced semidwarfness in the barley variety “Diamant” in Central Europe; another is gamma ray induced semidwarfness in the barley cultivar “Golden Promise” in the UK as well as in the durum wheat cultivar “Creso” in Italy. A significant economic impact also resulted from the cultivation of the cotton mutant cultivars “NIAB 78” and “Lu Mian No. 1” in Pakistan and China, respectively (Maluszynski, 1990). Rutger (1992) listed 11 rice mutant cultivars in Japan and China, each of which has been grown annually on 100,000 or more hectares. In ornamentals, induced mutations are now routinely used to develop new, more attractive cultivars (Broertjes and Van Harten, 1988). The development of efficient in vitro culture methods offers new, effective ways of overcoming difficulties in using induced mutations to generate desired variability in crops, particularly in vegetatively propagated crops. Among in vitro systems, doubled haploidy can be considered as an efficient tool for facilitating application of mutation techniques. The main advantages for sexually- and asexually-propagated plants are in facilitating screening for both dominant and recessive mutants which are homozygous early in the programme, in avoiding chimerism and in reducing the number of generations of progeny testing thus shortening the breeding cycle. The value of this methodology has already been clearly demonstrated in rapeseed breeding. This review will deal with the main theoretical considerations of these approaches, their development and applications.