Induced mutations in connection with biotechnology for crop improvement in Latin America. Proceedings of a final research co-ordination meeting

This publication results from the second Co-ordinated Research Project (CRP) on Plant Breeding and Genetics organized on a regional basis in Latin America. The present CRP and the previous one were initiated and implemented in response to the pressing need to enhance the productivity of economic plants, viz. food crops, fruits and ornamentals. Improvement of crop production has become the highest priority in most countries of Latin America, as in other regions. Breeding superior varieties is often the only feasible solution where inputs are limited; well adapted varieties are required to meet specific agro-environmental conditions. Such varieties provide yield stability on an economically required level. The most important and common factors limiting crop production are abiotic, e.g. cold, salinity, soil aluminium toxicity and drought; as well as biotic, e.g. diseases and pests. Modern biotechnology and induced mutations offer new means and significant potential to breed desired varieties in a relatively short time. Additionally, both approaches facilitate the breeding of some vegetatively propagated crops which until now were improved mainly through selection of rare spontaneous mutants in natural or cultivated populations. Using some of these techniques it recently became possible to produce, in some crops, true-to-type mutated lines or clones within a few months. Biotechnology can also facilitate selection, description and molecular characterization of promising mutants. Currently used DNA markers, such as restriction fragment length polymorphism (RFLP), random amplified polymorphic DNA (RAPD) as well as other polymerase chain reaction (PCR)-based techniques, were included in this CRP to benefit the important crops of this region. Also included in this CRP were doubled haploids (DH), which are obtained from anther or microspore cultures and are very suitable biotechnology methods. In connection with radiation-induced mutations, they can speed up conventional breeding programmes of seed propagated crops. Induced mutations, and to some extent also somaclonal variation, are practically the only new sources of variation available to breeders of vegetatively propagated crops because of the lack of genetic segregation. Micropropagation, somatic embryogenesis, protoplast fusion and protoplast regeneration, all techniques in which induced mutations were already successfully used to generate desired genetic variation, were employed in this CRP. The objectives of the CRP were mainly the following: To enhance regional co-operation in the field of radiation-induced mutations and related biotechnology and to stimulate induced mutation activities leading to the improvement of the productivity, yields and reliability of local cultivars by increasing their adaptability and tolerance to biotic and abiotic stresses; To investigate suitability of various local cultivars and methods for doubled haploid production (genotypic response), develop homozygous (DH) mutant lines with desired characters and initiate genetic and molecular analysis of promising mutants; To implement and develop protocols for in vitro induction of mutations in local cultivars of vegetatively propagated crops, evaluate stability and effectiveness of various in vitro culture methods for mutation induction and plant regeneration, evaluate frequency of selected mutants, develop true-to-type mutated clones and to initiate genetic and molecular analysis of promising mutants. This CRP made significant contributions in terms of improved, officially released, varieties and in producing promising mutant lines and clones which are currently under evaluation before release. Notable achievements were made in developing and adapting techniques for mutation induction using radiations and chemicals, in vitro cell and microspore cultures, and micropropagation. The significant achievements of this CRP cover a range of plants and issues dealing with major food crops (rice, wheat and barley), with the neglected cereals of South America (quinoa and kiwicha), and vegetatively propagated fruits (citrus, banana and avocado) and ornamentals. Important additional achievements were the formation of a network of co-operating scientists and the training of researchers. Finally, the know-how gained in this CRP is relevant to the same crops, and to other plants elsewhere. Thus, it will also benefit additional parts of the world