Genetic diversity and adaptedness in tetraploid Avena barbata and its diploid ancestors Avena hirtula and Avena wiestii.

Garcı́a, Pedro; Morris, M.I.; Miera, Luis E. Sáenz de; Allard, R. W.; Vega, M. Pérez de la; Ladizinsky, G.

doi:10.1073/pnas.88.4.1207

Cited by 25 publications

(8 citation statements)

References 8 publications

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“…It was argued that the main force responsible for the evolutionary change in the colonial populations of A. barbata was selection for particular combinations of alleles in response to different environments in California (Pérez de la Vega et al . 1991; Garcia et al . 1991; Allard et al .…”

Section: Discussionmentioning

confidence: 99%

Colonization history and introduction dynamics ofCapsella bursa‐pastoris(Brassicaceae) in North America: isozymes and quantitative traits

1999

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Multilocus isozyme genotypic composition for aspartate aminotransferase (AAT), leucine aminopeptidase (LAP) and glutamate dehydrogenase (GDH) was studied for Capsella in the source continent, Europe (9000 plants from 593 populations), and in the colonized continent, North America (2700 plants from 88 populations). North America was depauperate in the number of genotypes (by approximately 50%), but in terms of frequencies, a few genotypes were common and shared by both continents. Although some, very rare, genotypes were, however, unique for North America, our data provided no evidence to indicate that the introduced gene pools were reconstructed on a multilocus genetic basis after introduction. Instead, they argued for a considerable number of independent introduction events. Geographical distribution patterns of multilocus genotypes in Europe and North America were pronounced and enabled us to trace the colonization history of Californian Capsella back to Spanish ancestral populations and those of temperate North America back to temperate European gene pools. A random-block field experiment with 14 Californian populations from different climatic regions revealed that variation patterns of quantitative traits reflect ecotypic variation, and the ecological amplitude of Capsella in North America is similar to that in Europe, which can be traced back to the introduction of preadapted genotypes. It appears that certain multilocus isozyme genotypes are associated with certain ecotypes. The variable European gene pool of Capsella was essentially introduced into North America without major genetic changes.

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Section: Discussionmentioning

confidence: 99%

Colonization history and introduction dynamics ofCapsella bursa‐pastoris(Brassicaceae) in North America: isozymes and quantitative traits

1999

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“…It is possible that differences in adaptedness between these two genotypes may have been due entirely to the main effects of these five loci but the very large number of different patterns in which the alleles of the 14-locus genotypes occur in the diploid suggest that two-locus, three-locus and higher-order interactions were also involved . In fact discrete loglinear analyses showed that many multilocus interactions are highly significant statistically but others are nonsignificant (Perez de la Garcia et al ., 1991) . Within-population diversity varied from none for Sites I and 2, to small for Site 3 (only two 14-locus genotypes present), to substantial for Sites 4 and 5 (eight different 14-locus genotypes present), to high for the five remaining sites (13 to 36 different 14-locus genotypes present).…”

Section: Avena Hirtula (Ah) and A Barbata (Ab)mentioning

confidence: 99%

“…In recent years it has been found that examination of changes in the frequencies of discretely distinguishable alleles and genotypes of morphological, disease resistance, allozyme, restriction fragment, and microsatellite loci that occurred during the domestication process allow deductions concerning the genetic mechanisms that have led to improved adaptedness (e.g . Clegg & Allard, 1972 ;Allard, 1988Allard, , 1990 ; Perez de la Vega, Garcia et al ., 1991 ;Allard et al ., 1993 ;Saghai Maroof et al, 1994;Cluster & Allard, 1995) . In all cases that have been studied in detail it has been found that population behavior can be explained on the basis of selection acting on the chromosomal segments in which the marker loci reside ; thus marker assisted dissection of the genetic basis of adaptedness is feasible and a substantial literature has built up, too large to review in the time allotted .…”

Section: Introductionmentioning

confidence: 99%

Genetic basis of the evolution of adaptedness in plants

Allard

1996

Euphytica

114

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Adaptedness is both complexly inherited and much affected by environment: consequently the genetic mechanisms that have led to improvements in adaptedness have been difficult to identify and to quantify . Recently it has been shown that `marker assisted dissection' of adaptedness based on changes in the frequencies of discretely inherited alleles of loci of various kinds (e.g . allozyme, restriction fragment, microsatellite loci) is practicable . I will illustrate marker assisted analysis of the genetic basis of adaptedness with a sample of allozyme data from three species groups, two heavily selfing groups (two wild Avena species and barley) and one outcrossing species (corn, maize) . The results lead to three main conclusions : (1) that the single most important genetic mechanism in all three species groups was the assembly of favorable epistatic combinations of alleles of different loci by means of recurring cycles of selection, intercrossing superior selects, and inbreeding to near homozygosity leading to stable superior multilocus genotypes adapted to specific habitats ; (2) that exploitation of favorable interactions among alleles of the same locus played a significant role in tetraploid A . barbata and probably also in single-cross maize hybrids ;(3) that purifying selection (elimination of deleterious alleles) played a small role in all three species groups . These results indicate that marker alleles provide applied breeders with effective ways to identify, track, and incorporate regions of chromosomes with favorable effects of adaptedness into improved cultivars .

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“…The one percent of outcrossing that occurs leads to recombination that produces numerous different interlocus allelic configurations within local populations, whereas the 99% of selfing restricts recombination sufficiently to protect favorable interallelic associations from being broken up by segregation before they can be tested by selection (11,12). The tetraploidy of A. barbata allows the development and fixation of heteroallelic intralocus associations of alleles (13). Thus the mating system of A. barbata, in combination with differing modes of selection associated with local environmental heterogeneity, appears to have led to the development of a pathwork pattern of differing multilocus genetic organizations in Spain.…”

Section: Loci Of Group 2 (Californian Xeric Allelesmentioning

confidence: 99%

Multilocus genetic structure of ancestral Spanish and colonial Californian populations of Avena barbata.

Vega

Garcı́a

Allard

1991

Proc. Natl. Acad. Sci. U.S.A.

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We have applied a multivariate log-inear technique to the analysis ofinterlocus allelic associations among 14 allozyme loci in a sample of 4011 plants from 42 Spanish populations of Avena barbata. The loci fell into three natural groups offive, five, and four loci. The five loci of the first group are invariant, or nearly so, throughout the range of the species. The genetic organization of the loci of this set is defined by a single five-locus genotype; each allele of this predominant genotype is a "wild-type" allele that contributes favorably to adaptedness in all single-locus and multilocus configurations regardless of environment. Although allelic diversity is high in Spain for the nine loci of the second and third sets, log-linear analyses showed that these loci are tied together in Spanish populations through complex networks of overlapping lowerorder interlocus interactions. The ancestral Spanish and colonial Californian gene pools are closely similar in allelic composition on a locus-by-locus basis; however, Spanish allelic configurations at two-locus and higher-order levels are usually different from and much less tightly organized than in Californian populations. We conclude that the major force involved in the evolution of the colonial populations was selection that led to reorganization, at the interlocus level, of the ancestral Spanish alelic ingredients into different multilocus genotypes adapted to Californian habitats.The Slender Wild Oat, Avena barbata Pott ex Link., is a diploidized tetraploid grass that is distributed over a vast area from the Western Mediterranean Basin across the Middle East to Nepal (1). Historical records indicate that A. barbata was introduced to California from Spain in the period of exploration and colonization and that the species soon became a major component of a number of distinct habitats in California (2). Detailed studies of the ecogenetics of A. barbata in California (3) have established that the species is now differentiated into several ecotypes marked by specific multilocus combinations of alleles of discretely identifiable morphological, allozyme, and restriction-fragment variants and that these ecotypes are distributed in patterns that precisely overlay environmental heterogeneity, especially heterogeneity for available moisture and for temperature. A. barbata occurs in two major climatic zones in California (4), the Mediterranean hot summer zone, which includes the extensive semiarid grasslands and oak savannah of the foothills bordering the Central Valley, and the Mediterranean cool summer zone, which includes the intermontane regions of the Pacific coastal strip and the higher foothills of the Sierra Nevada mountains; the Mediterranean cool summer zone is characterized by mild wet winters and a diversity of habitats varying from mesic to semiarid. The great majority of populations in the hot summer zone are nearly monomorphic for a specific combination of alleles designated xeric, The publication costs of this article were defrayed in part by page...

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Genetic diversity and adaptedness in tetraploid Avena barbata and its diploid ancestors Avena hirtula and Avena wiestii.

Cited by 25 publications

References 8 publications

Colonization history and introduction dynamics ofCapsella bursa‐pastoris(Brassicaceae) in North America: isozymes and quantitative traits

Colonization history and introduction dynamics ofCapsella bursa‐pastoris(Brassicaceae) in North America: isozymes and quantitative traits

Genetic basis of the evolution of adaptedness in plants

Multilocus genetic structure of ancestral Spanish and colonial Californian populations of Avena barbata.

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