Populations Of Crop Wild Relatives Research Articles

The Genetic Diversity of Cranberry Crop Wild Relatives, Vaccinium macrocarpon Aiton and V. oxycoccos L., in the US, with Special Emphasis on National Forests.

Knowledge of the genetic diversity in populations of crop wild relatives (CWR) can inform effective strategies for their conservation and facilitate utilization to solve agricultural challenges. Two crop wild relatives of the cultivated cranberry are widely distributed in the US. We studied 21 populations of Vaccinium macrocarpon Aiton and 24 populations of Vaccinium oxycoccos L. across much of their native ranges in the US using 32 simple sequence repeat (SSR) markers. We observed high levels of heterozygosity for both species across populations with private alleles ranging from 0 to 26. For V. macrocarpon, we found a total of 613 alleles and high levels of heterozygosity (HO = 0.99, HT = 0.75). We also observed high numbers of alleles (881) and levels of heterozygosity (HO = 0.71, HT = 0.80) in V. oxycoccos (4x). Our genetic analyses confirmed the field identification of a native population of V. macrocarpon on the Okanogan-Wenatchee National Forest in the state of Washington, far outside the previously reported range for the species. Our results will help to inform efforts of the United States Department of Agriculture Agricultural Research Service (USDA-ARS) and the United States Forest Service (USFS) to conserve the most diverse and unique wild cranberry populations through ex situ preservation of germplasm and in situ conservation in designated sites on National Forests.

Genetic diversity and differentiation in Patellifolia (Amaranthaceae) in the Macaronesian archipelagos and the Iberian Peninsula and implications for genetic conservation programmes

This is the first comprehensive investigation of the patterns of genetic diversity of Patellifolia species. The main objective of our research work is to determine Most Appropriate crop Wild relative Populations (MAWP) suited to conserve in situ wild relatives of the sugar beet. Individual plant samples of P. patellaris were collected at 26 and of P. procumbens/P. webbiana at seven sites and analysed with 24 and 22 microsatellite markers, respectively. On average 15 alleles per locus were found within the set of 581 P. patellaris and an average of 12 alleles per locus in the set of 172 P. procumbens/P. webbiana individuals. The factorial analysis showed diversity patterns which agree well with the geographic origin of the samples. The genetic data suggest that P. patellaris reproduces mainly by self-fertilisation while P. procumbens/P. webbiana have the signature of out-breeders. The measure Δ was used to calculate the genetic distance of each occurrence to the pooled remaining occurrences, the complement. Occurrences with either the lowest or the highest genetic distance to the complement are particularly suited to conserve the genetic diversity of the species. Eight occurrences of P. patellaris, two of P. procumbens and one for P. webbiana were determined according to this scheme, proposed as MAWP and recommended for the establishment of genetic reserves.

Molecular diversity and landscape genomics of the crop wild relative Triticum urartu across the Fertile Crescent.

Modern plant breeding can benefit from the allelic variation that exists in natural populations of crop wild relatives that evolved under natural selection in varying pedoclimatic conditions. In this study, next-generation sequencing was used to generate 1.3 million genome-wide single nucleotide polymorphisms (SNPs) on ex situ collections of Triticum urartu L., the wild donor of the Au subgenome of modern wheat. A set of 75511 high-quality SNPs were retained to describe 298 T. urartu accessions collected throughout the Fertile Crescent. Triticum urartu showed a complex pattern of genetic diversity, with two main genetic groups distributed sequentially from west to east. The incorporation of geographical information on sampling points showed that genetic diversity was correlated to the geographical distance (R2 =0.19) separating samples from Jordan and Lebanon, from Syria and southern Turkey, and from eastern Turkey, Iran and Iraq. The wild emmer genome was used to derive the physical positions of SNPs on the seven chromosomes of the Au subgenome, allowing us to describe a relatively slow decay of linkage disequilibrium in the collection. Outlier loci were described on the basis of the geographic distribution of the T. urartu accessions, identifying a hotspot of directional selection on chromosome 4A. Bioclimatic variation was derived from grid data and related to allelic variation using a genome-wide association approach, identifying several marker-environment associations (MEAs). Fifty-seven MEAs were associated with altitude and temperature measures while 358 were associated with rainfall measures. The most significant MEAs and outlier loci were used to identify genomic loci with adaptive potential (some already reported in wheat), including dormancy and frost resistance loci. We advocate the application of genomics and landscape genomics on ex situ collections of crop wild relatives to efficiently identify promising alleles and genetic materials for incorporation into modern crop breeding.

Assessment of spatial–temporal variation in natural populations of Brassica incana in south Italy: implications for conservation

Brassica incana is a secondary-gene pool wild relative of Brassica oleracea. Twenty-two B. incana populations are recorded in Italy, where the species has recently been pointed out as in priority need of conservation. While data on the spatial and temporal variation of B. incana Italian populations are completely lacking, this information is useful in conservation planning for this species. Three populations from the Sorrento peninsula and from the islands of Ischia and Capri, collected in 1984 and 2012, were characterised for 12 morpho-phenological and 21 genetic traits to assess their spatial–temporal variation. The populations were quite different for morpho-phenological and genetic traits. Spatial differentiation was high and easily explained by the isolation. Temporal differentiation between the Sorrento and Ischia populations was high and explained by a reduction in the population census across time, while it was not significant between the two Capri accessions as such pointing to a major effect of genetic drift. Numerical dimension is extremely relevant in evaluating conservation priorities since it has a major impact on population dynamics over time. The Sorrento and Ischia populations are under threat and urgently need conservation actions, suggesting an alarming scenario for the survival of other crop wild relative populations which are similar in census. Our data also show that, in an allogamous and self-incompatible species like B. incana, populations of 100–200 individuals maintain high allelic diversity. According to obtained results, natural populations of species with similar reproductive system and census can be considered at low risk of genetic erosion.

Introgression of transgenic crop alleles: Its evolutionary impacts on conserving genetic diversity of crop wild relatives

AbstractEffective conservation of crop wild relative (CWR) species is essential for the sustainable use and genetic improvement of crop varieties, which offers greater opportunities for world food security, particularly in modern agroecosystems where CWR diversity is under severe threat. Factors such as habitat fragmentation, human disturbances, global climate change, and invasion of harmful alien species have been identified to be responsible for losses and threats to CWR diversity. However, a neglected factor, gene introgression from domesticated species through repeated outcrossing, may have a significant impact on CWR diversity. Introgression can influence genetic diversity and evolutionary processes of CWR populations through effects such as demographic swarming, genetic assimilation, and selective sweep. When largely enhancing or reducing fitness of wild plants, the introgression of crop genes will impose more significant genetic and evolutionary impacts on CWR populations, leading to undesired consequences for conserved CWR populations and species. This situation is particularly true when genetically engineered (GE) crops are deployed for commercial cultivation. It is argued that a GE crop usually contains transgenes with strong natural selection advantages, and such transgenes introgressed into CWR populations may have strong impacts on their genetic diversity and evolutionary processes, threatening their conservation. This article reviews the challenge of crop–wild gene flow, and particularly transgene introgression from GE crops, for the in situ conservation of wild relative species. The design of effective management strategies for conserving CWR species under the scenario of extensive cultivation of GE crops is also discussed.

On the 'lost' crops of the neolithic Near East.

The claim that the 'classic' eight 'founder crop' package (einkorn wheat, emmer wheat, barley, lentil, pea, chickpea, bitter vetch, and flax) underlying the emergence of agriculture in the Near East is a relic of a larger number of domesticated species is addressed. The 'lost' crops concept relies on the idea that additional taxa were at certain points in time and in certain locations genuine crops, which were later abandoned. The issue is highly relevant to the debate concerning mono- versus polyphyletic domestication, because if there were numerous 'false starts' that were subsequently lost, this implies that plant domestication occurred over a protracted time period, and across a wide geographic range. Different criteria were used for declaring those taxa as 'lost' crops, including, but not limited to (i) identification in archaeobotanical assemblages of grains from species which are not known as crops at present; (ii) identification of such grains in what is interpreted to have been Neolithic storage facilities; and (iii) recent botanical observations on populations of crop wild relatives in disturbed habitats. The evidence for four presumed 'lost' crops (wild oat, rambling vetch, rye, and wild black lentil) and the broad bean is evaluated, and discussed in light of data on Croatian and Israeli wild pea, and Moroccan wild lentil in disturbed habitats. Based on present knowledge, the broad bean might emerge as a founder crop (without an identified wild progenitor). The same may hold true for rye, which was never lost since its adoption in the Pre-Pottery Neolithic B period in Anatolia. In the remaining three cases, there are alternative, more likely, explanations for the archaeological finds or the recent botanical observations rather than 'lost' domestication episodes.

<i>In Situ</i> Conservation of Wild Rice Populations: A Targeted Study of Common Wild Rice <i>Oryza rufipogon</i> from China

Although great accomplishments of in situ conservation have been made during the last decade throughout the world, there is an urgent need to conduct more targeted research to explore many basic questions about crop wild relatives (CWR) in situ conservation such as how to better identify and manage the target in situ conservation populations of CWR. In this study, we performed an extensive field investigation of 201 natural populations or habitats of O. rufipogon, a seriously endangered wild progenitor of cultivated rice in China. Our updated information suggests that: 1) the majority of the natural populations have been extinct throughout China, which leads to serious fragmentation of the population system as a whole; and 2) the survived populations have become small in size and thus fragmented within the population as a result of the loss of subpopulations. To assess the relationships between the biodiversity education and conservation of wild rice, we employed participatory approaches in the field investigation. Our data indicate that the continuous rapid decline of biodiversity education seemed closely related to the extinction of wild rice germplasm. These findings imply the potential necessity and huge challenge for making in situ conservation plans in the future. By means of our understanding of ecogeography, sociology and culture, and population genetics of the species, we propose a strategy for selecting in situ conservation locations as well as priority sites for establishing in situ conservation practices in China.

Direct comparison of pollen-mediated movement of native and engineered genes

Despite the commercial approval of twenty-five transgenic crops in the U.S. as of mid-1996, concern is still being expressed regarding the potential risks associated with genetically engineered crops. One recurring issue is the possibility of pollen-mediated escape of engineered genes into populations of crop wild relatives. To address this concern, the scientific community has depended on literature on pollen dispersal generated from non-transgenic organisms. Utilization of this information requires the assumption that the pollen mediated movement of native and transgenes is the same. To test the validity of this assumption, we directly compared the pollen-mediated gene movement of native and engineered marker genes using melon plants (Cucumis melo L.) expressing dominant morphological and transgenic traits. Movement into both contiguous border plots and non-contiguous satellite plots were monitored. Dispersal of the native gene and transgene into the satellite plots was identical. Dispersal of the two traits into the plot borders was nearly identical. Of the nearly 4600 seedlings screened for both morphological (presence of green vs. virescent cotyledons) and transgene movement (presence of NPT II protein by ELISA), in no case was the NPT II gene observed in the absence of green cotyledons. However, 39 seedlings were green but did not express NPT II as measured by ELISA. PCR analysis revealed transgene inactivation as a cause of the NPT II ELISA-seedlings.