[en] An Advisory Group Meeting was convened to consider possibilities and limitations of induced mutation technology for the purpose of domestication, to discuss the methodology, identify target species, and to define the character changes required. The meeting took place in Vienna at the IAEA Headquarters from 17-21 November 1986. This publication contains the review papers as well as the results of discussions in the form of conclusions and recommendations. As a supplement, a bibliography has been added. Refs, figs and tabs

[en] Published in summary form only

[en] The region of semi-arid tropics is the most famine prone area of the world. This region with nearly one billion people extends across some 20 million square kilometres. Major domesticated cereals adapted to semi-arid regions are sorghum (Sorghum bicolor (L.) Moench), foxtail millet (Setaria italica (L.) P. Beauv.) and pearl millet (Pennisetum glaucum (L.) R. Br.). Several minor cereals are grown as speciality crops, or harvested in the wild in times of severe drought and scarcity. Important in the African Sahel are the fonios Digitaria iburua Stapf, D. exilis (Kapist) Stapf and Brachiaria deflexa (Schumach). C.E. Hubbard. These species are aggressive colonizers and are commonly encouraged as weeds in cultivated fields. Sown genotypes differ from their close wild relatives primarily in the lack of efficient natural seed dispersal. The fonios lend themselves to rapid domestication. Several wild cereals extend well beyond the limits of agriculture into the Sahara. Commonly harvested are the perennial Stipagrostis pungens and Panicum turgidum, and the annual Cenchrus biflorus (kram-kram). Kram-kram yields well under extreme heat and drought stress, and holds promise as a domesticated cereal. Sauwi millet (Panicum sonorum) is promising cereal in arid northwestern Mexico. (author). 31 refs

[en] Though fruit gathering from the wild began long before domestication, fruit tree domestication started only after the establishment of grain agriculture. Banana, fig, date, grape and olive were among the first fruit trees domesticated. Most fruit trees are outbreeders, highly heterozygous and vegetatively propagated. Knowledge of genetics and economic traits controlled by major genes is limited. Ease of vegetative propagation has played a prominent part in domestication; advances in propagation technology will play a role in domestication of new crops. Changes toward domestication affected by major genes include self-fertility in peach, apricot and sour cherry, while the emergence of self-fertile almond populations is more recent and due probably to introgression from Amygdalus webbii. Self-compatibility in the sweet cherry has been attained only by pollen irradiation. A single gene controls sex in Vitis. Wild grapes are dioecious, with most domesticated cultivars hermaphrodite, and only a few females. In the papaya changes from dioecism to hermaphroditism have also occurred. Self-compatible systems have also been selected during domestication in Rubus. Changes towards parthenocarpy and seedlessness during domestication occurred in the banana, citrus, grape, fig and pineapple. In the banana, parthenocarpy is due to three complementary dominant genes; stenospermocarpy in the grape depends on two complementary recessive genes; parthenocarpy and sterility in citrus seems more complicated; however, it can be induced in genetic material of suitable background with ease by irradiation. Presence of persistent syconia in the fig is controlled by a mutant allele P dominant to wild +. Thornlessness in blackberry is recessive, while in the pineapple spineless forms are dominant. Changes affecting fruit composition owing to major genes include the disappearance of amygdalin present in bitter almonds (bitter kernel recessive to sweet), shell hardness in almond, and a recessive controlling low acid fruit in apple. (author). 55 refs

[en] Limnanthes (family Limnanthaceae) species are herbaceous winter annuals with seed oil consisting of a high proportion of long chain fatty acids (C₂₀, C₂₂) with many potential industrial uses. Domestication efforts have largely involved biosystematic studies on genetic resources, agronomic evaluation of yield and cultural practices, and population improvement using mass and family selection methods. Significant gains which have been made in seed yield and its various components clearly make it a promising new crop. However, a wide variety of intra- and interspecific hybrid materials have only now become available for basic genetic research and accelerated breeding work. A search for both naturally occurring and induced mutations for modifying plant architecture, seed retention and increased self-fertility is highly recommended in order to facilitate commercial production as well as further gains in yield and adaptability, utilizing a combination of Mendelian and biometrical approaches. In parallel with Cuphea and other industrial crop breeding experience, Limnanthes research clearly illustrates the need for sustained and larger investments, a broadbased scientific approach, and some serendipitous (e.g. marketing) developments. (author). 25 refs, 1 fig., 5 tabs

[en] The distribution of grain legume species is not random in Leguminosae. There are two major concentrations in the Phaseoleae and the Vicieae, with the majority in the Phaseoleae. Within the tribe further concentration is apparent in the subtribe Phaseolinae and at the generic level in Phaseolus and Vigna. Since several members of both genera have been domesticated over a large portion of their respective geographic ranges, it is suggested that these taxa and their close relatives are particularly responsive to the particular selection pressures imposed under domestication. As domestication itself is opportunistic, it is possible that considerable potential for domestication remains unexploited in species with distributions remote from ancient agricultural hearths. Some of these species may occur in difficult and marginal environments for agriculture where adaptation of present crop species is poor. They could be the starting point for the domestication and evolution of new crops for problem environments. The major obstacle to such a development is the lack of sufficient genetic variability of the right kind. This deficiency might well be made good by applying techniques of artificial mutagenesis prior to selection. By applying Vavilov's law of homologous series it should be possible to set realistic objectives and monitor progress towards the goals of selection which have been defined. (author). 6 refs, 5 tabs

[en] In order to facilitate domestication and breeding of new or underexploited crop species, the genetic basis of many traits must be critically investigated, and both naturally occurring and induced mutations should be utilized. Classically, most breeding procedures have invoked the dichotomy of major genes versus polygenes (or discrete versus continuously varying traits) which is briefly reviewed here from several viewpoints. Clearly, the evidence for two distinct classes of genes (or gene effects on phenotype) and traits is largely a product of different forms of genetic analyses and their primary objectives as well as of researchers' expectations. Superimposed on the simplest Mendelian ratios and genome maps are numerous sources of molecular variation and gene expression at many levels of phenotypic description. Many attempts to delineate developmental pathways and to identify genes controlling discrete vs. quantitative phenotypic variation have resulted in emphasis on multigenic models with specific gene effects at mappable loci but nonetheless modified by small effects. Thus, quantitative genetic variation may arise from multi-genic and multi-allelic systems of both structural and regulatory gene action and gene interactions which, from an empirical breeding perspective, might be adequately described by the biometrical and evolutionary models. Polygenic analyses were conceptually based on genetic parameters in these models (as caricatures of reality) but efforts to modify or reject them by identifying and mapping sources of phenotypic variation through newer genetic methods are likely to enrich and not displace biometrical methods. Domestication programmes, in particular, should employ the entire array of genetic discoveries and methodologies. (author). 71 refs, 1 fig., 1 tab

[en] From the approximately 200,000 species of flowering plants known, only about 200 have been domesticated. The process has taken place in many regions over long periods. At present there is great interest in domesticating new species and developing new uses for existing ones in order to supply needed food, industrial raw materials, etc. It is proposed that major gene mutations were important in domestication; many key characters distinguishing cultivated from related wild species are controlled by one or very few major genes. The deliberate effort to domesticate new species requires at least the following: identification of needs and potential sources, establishment of suitable niches, choice of taxa to be domesticated, specification of the desired traits and key characters to be modified, as well as the potential role of induced mutations. (author). 14 refs

[en] Cuphea is a herbaceous summer annual plant native to Central America. Its seed oil contains high amounts of medium chain fatty acids, depending on the species with C8, C10 and C12, respectively, amounting to sometimes more than 80% of the total fatty acids. The report summarizes over 10 years' research on the domestication of this genus. From extensive tests on the production potentials, some of these on a worldwide scale, a few most promising genotypes of the section Heterodon have been selected from among 45 species and 180 accessions for further genetic improvements. Chemical mutagenesis was effective in promoting the domestication programme and mutants have been obtained with, e.g. non-sticky hairiness, monoculm stem, and determinate growth by stem fasciation. However, the most desired mutation to indehiscent fruits has not yet been discovered within the selected productive Cuphea species. This problem of early seed dispersal in Cuphea may alternatively necessitate technical solutions, which also have been developed with a vacuum picking machine for multiple harvests. From the findings presented, some general considerations are deduced regarding the mutability of traits characterizing interspecific variation as well as regarding the need for improving the genetic background of mutants by recurrent selection procedures. (author). 17 refs, 2 figs, 9 tabs

[en] The role of cytogenetics in plant domestication is not as direct as that of plant breeding, agronomy or crop botany. Five major areas of cytogenetic interest in plant domestication are distinguished: analysis of the genetic structure of the species and its relation with other species, including genome analysis; monitoring of chromosomal, including meiotic, consequences of drastic genetic alterations such as artificial mutations (including somaclonal variation) and interspecific hybridization (including complete and partial protoplast fusion); induction, monitoring and adjustment of auto- and allopolyploidy; introduction of alien chromosome segments by meiotic manipulation and translocation; adjustment of the genetic transmission system, such as the construction of systems for hybrid varieties, allopolyploidization of (partial) autopolyploids or non-functional allopolyploids and permanent complex translocation heterozygotes. It is concluded that the last three areas are of interest only in the context of large programmes with sufficient and guaranteed input and continuity. (author). 23 refs