The domestication of artichoke and cardoon: from Roman times to the genomic age

BACKGROUND: The history of domestication of artichoke and leafy cardoon is not yet fully understood and when and where it occurred remains unknown. Evidence supports the hypothesis that wild cardoon is the wild progenitor of both these crops. Selection for large, non-spiny heads resulted in artichoke and selection for non-spiny, large stalked tender leaves resulted in leafy cardoon. The two crops differ in their reproductive system: artichoke is mostly vegetatively propagated and perennial, while leafy cardoon is seed propagated and mostly grown as an annual plant. Here, new trends in artichoke cultivation are analysed, while the consequences of these tendencies on the conservation of artichoke genetic resources are highlighted. SCOPE: The historical and artistic records, together with recent literature on genetics and biosystematics, are examined with the aim of achieving a better understanding of the present-day knowledge on the domestication of these two crops. CONCLUSIONS: Historical, linguistic and artistic records are consistent with genetic and biosystematic data and indicate that the domestication of artichoke and cardoon diverged at different times and in different places. Apparently, artichoke was domesticated in Roman times, possibly in Sicily, and spread by the Arabs during early Middle Ages. The cardoon was probably domesticated in the western Mediterranean in a later period.     

The complex history of the domestication of rice

BACKGROUND: Rice has been found in archaeological sites dating to 8000 bc, although the date of rice domestication is a matter of continuing debate. Two species of domesticated rice, Oryza sativa (Asian) and Oryza glaberrima (African) are grown globally. Numerous traits separate wild and domesticated rices including changes in: pericarp colour, dormancy, shattering, panicle architecture, tiller number, mating type and number and size of seeds. SCOPE: Genetic studies using diverse methodologies have uncovered a deep population structure within domesticated rice. Two main groups, the indica and japonica subspecies, have been identified with several subpopulations existing within each group. The antiquity of the divide has been estimated at more than 100 000 years ago. This date far precedes domestication, supporting independent domestications of indica and japonica from pre-differentiated pools of the wild ancestor. Crosses between subspecies display sterility and segregate for domestication traits, indicating that different populations are fixed for different networks of alleles conditioning these traits. Numerous domestication QTLs have been identified in crosses between the subspecies and in crosses between wild and domesticated accessions of rice. Many of the QTLs cluster in the same genomic regions, suggesting that a single gene with pleiotropic effects or that closely linked clusters of genes underlie these QTL. Recently, several domestication loci have been cloned from rice, including the gene controlling pericarp colour and two loci for shattering. The distribution and evolutionary history of these genes gives insight into the domestication process and the relationship between the subspecies. CONCLUSIONS: The evolutionary history of rice is complex, but recent work has shed light on the genetics of the transition from wild (O. rufipogon and O. nivara) to domesticated (O. sativa) rice. The types of genes involved and the geographic and genetic distribution of alleles will allow scientists to better understand our ancestors and breed better rice for our descendents.     

Architectural evolution and its implications for domestication in grasses

BACKGROUND: The cereal crops domesticated from grasses provide a large percentage of the calories consumed by humans. Domestication and breeding in individual cereals has historically occurred in isolation, although this is rapidly changing with comparative genomics of the sequenced or soon-to-be sequenced genomes of rice, sorghum, maize and Brachypodium. Genetic information transferred through genomic comparisons is helping our understanding of genetically less tractable crops such as the hexaploid wheats and polyploid sugarcane, as well as the approx. 10 000 species of wild grasses. In turn, phylogenetic analysis helps put our knowledge of the morphology of cereal crops into an evolutionary context. GRASS ARCHITECTURE: Domestication often involves a change in the pattern and timing of branching, which affects both vegetative and inflorescence architecture, and ultimately yield. Cereal grasses exhibit two main forms of vegetative architecture: the pooid and erhartoid cereals such as wheat and rice have multiple basal tillers, while panicoid cereals such as maize, sorghum and the millets have few tillers or even only a single main stem. These differences are reflected in the differences between the wild species of pooid and some erhartoid grasses, which emphasize basal branching over axillary branching, and the panicoid grasses, where axillary branching is more frequently found. A combination of phylogenetic and genomic analysis is beginning to reveal the similarities and differences between different cereal crops, and relate these to the diversity of wild grasses to which they are related. Recent work on genes controlling branching emphasizes that developmental genetics needs to be viewed in both an evolutionary and ecological framework, if it is to be useful in understanding how morphology evolves. Increasingly, exploring the phylogenetic context of the crop grasses will suggest new ways to identify and create combinations of morphological traits that will best suit our future needs.     

Genetic variation and differentiation in captive and wild zebra finches (Taeniopygia guttata)

The zebra finch (Taeniopygia guttata) is a small Australian grassland songbird that has been domesticated over the past two centuries. Because it is easy to breed in captivity, it has become a widely used study organism, especially in behavioural research. Most work has been conducted on domesticated populations maintained at numerous laboratories in Europe and North America. However, little is known about the extent to which, during the process of domestication, captive populations have gone through bottlenecks in population size, leading to inbred and potentially genetically differentiated study populations. This is an important issue, because (i) behavioural studies on captive populations might suffer from artefacts arising from high levels of inbreeding or lack of genetic variation in such populations, and (ii) it may hamper the comparability of research findings. To address this issue, we genotyped 1000 zebra finches from 18 captive and two wild populations at 10 highly variable microsatellite loci. We found that all captive populations have lost some of the genetic variability present in the wild, but there is no evidence that they have gone through a severe bottleneck, as the average captive population still showed a mean of 11.7 alleles per locus, compared to a mean of 19.3 alleles/locus for wild zebra finches. We found significant differentiation between the captive populations (F(ST) = 0.062). Patterns of genetic similarity closely match geographical relationships, so the most pronounced differences occur between the three continents: Australia, North America, and Europe. By providing a tree of the genetic similarity of the different captive populations, we hope to contribute to a better understanding of variation in research findings obtained by different laboratories.     

Behavioral syndromes and the evolution of correlated behavior in zebrafish

Studies of "behavioral syndromes" in different populations andspecies of animals can be used to shed light on the underlyingmechanisms of evolution. For example, some personality syndromessuggest the existence of an underlying hormonal link, whereasother relationships between boldness and aggression appear tobe the result of similar selective pressures. Here, we used1 wild-derived and 2 laboratory strains of zebrafish (Daniorerio) to examine relationships among 5 behavioral measures:shoaling, activity level, predator approaches, latency to feedafter a disturbance, and biting to a mirror stimulus. We foundevidence of an activity syndrome, as if underlying metaboliccosts influence variation in multiple forms of behavior. Evidencefor a relationship between boldness and aggression was alsoapparent but depended both on strain and which specific behaviorpatterns were identified as measures of "boldness." Althoughsome comparisons of laboratory and wild-derived strains wereconsistent with a domestication syndrome, others were not. Mostobserved relationships were relatively weak and occasionallyinconsistent, arguing against strong underlying genetic linkagesor pleiotropic effects relating any of the behavioral measures.Instead, it may be more important to study the details of selectivecontext or the long-term impact of linkages between some, butnot all, of a large set of genes influencing complex behavioraltraits. We found profound differences among strains in mostbehavior patterns, but few sex differences. One strain (TM1)was consistently different from the others (SH and Nadia) beingmore social, more likely to approach predators, and taking lesstime to recover from disturbance than were the other 2 strains.     

Stress and domestication traits increase the relative fitness of crop-wild hybrids in sunflower

After a decade of transgenic crop production, the dynamics of gene introgression into wild relatives remain unclear. Taking an ecological genetics approach to investigating fitness in crop-wild hybrid zones, we uncovered both conditions and characteristics that may promote introgression. We compared diverse crop-wild hybrid genotypes relative to wild Helianthus annuus under one benign and three stressful agricultural environments. Whereas relative fitness of crop-wild hybrids averaged 0.25 under benign conditions, with herbicide application or competition it reached 0.45 and was more variable. In some instances, hybrid fitness matched wild fitness (approximately 1). Thus, wild populations under agronomic stress may be more susceptible to introgression. Although 'domestication' traits are typically considered unlikely to persist in wild populations, we found some (e.g. rapid growth and early flowering) that may enhance hybrid fitness, especially in stressful environments. Rigorous assessment of how particular genotypes, phenotypes, and environments affect introgression will improve risk assessment for transgenic crops.