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5 resultados encontrados para: AUTOR: Mercer, Kristin L
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1.
- Artículo con arbitraje
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Structure of local adaptation across the landscape: flowering time and fitness in Mexican maize (Zea mays L. subsp. mays) landraces
Mercer, Kristin L. (autor) ; Perales Rivera, Hugo Rafael (autor) ;
Contenido en: Genetic Resources and Crop Evolution Vol. 66, no. 1 (January 2019), p. 27-45 ISSN: 0925-9864
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In crop centers of origin and diversity, often biotic and abiotic conditions vary across the landscape creating the possibility for local adaptation of crops, whereby local landraces perform better than non-local ones under local conditions. By studying patterns of local adaptation we can better understand the degree of adaptation of landraces, phenotypic mechanisms driving that adaptation, and the plastic responses of adapted populations to environmental change. Studying these basic processes in crop centers of origin and diversity improves basic understanding of adaptive evolution and provides insight for existing farming systems encountering climate change. Using maize landraces collected and reciprocally transplanted in the field in two years along an elevational gradient in Chiapas, Mexico, we aimed to understand their degree of local adaptation, the distribution of adaptive diversity within elevations, and how landraces compared to improved varieties in their responses to environmental variation. We found some patterns consistent with local adaptation among the landraces, although the degree of adaptation differed across measures of fitness components and years. Flowering time variables showed more variability within elevations than total fitness estimates or fitness components did. Improved varieties, like low elevation landraces, were not well-adapted to conditions at higher elevations, although they did possess some beneficial traits. These data reaffirmed experimentally the local adaptation of landraces and their difficulty in reproducing under novel conditions, and indicated the importance of landraces for high productivity (especially in middle and high elevation systems).


2.
- Artículo con arbitraje
Differentiated transcriptional signatures in the maize landraces of Chiapas, Mexico
Kost, Matthew A. (autor) ; Perales Rivera, Hugo Rafael (coaut.) ; Wijeratne, Saranga (coaut.) ; Wijeratne, Asela J. (coaut.) ; Stockinger, Eric J. (coaut.) ; Mercer, Kristin L. (coaut.) ;
Contenido en: BMC Genomics Vol. 18, no. 1, Article number 707 (September 2017), p. 1-14 ISSN: 1471-2164
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Background: Landrace farmers are the keepers of crops locally adapted to the environments where they are cultivated. Patterns of diversity across the genome can provide signals of past evolution in the face of abiotic and biotic change. Understanding this rich genetic resource is imperative especially since diversity can provide agricultural security as climate continues to shift. Results: Here we employ RNA sequencing (RNA-seq) to understand the role that conditions that vary across a landscape may have played in shaping genetic diversity in the maize landraces of Chiapas, Mexico. We collected landraces from three distinct elevational zones and planted them in a midland common garden. Early season leaf tissue was collected for RNA-seq and we performed weighted gene co-expression network analysis (WGCNA). We then used association analysis between landrace co-expression module expression values and environmental parameters of landrace origin to elucidate genes and gene networks potentially shaped by environmental factors along our study gradient. Elevation of landrace origin affected the transcriptome profiles. Two co-expression modules were highly correlated with temperature parameters of landrace origin and queries into their 'hub' genes suggested that temperature may have led to differentiation among landraces in hormone biosynthesis/signaling and abiotic and biotic stress responses. We identified several 'hub' transcription factors and kinases as candidates for the regulation of these responses.

Conclusions: These findings indicate that natural selection may influence the transcriptomes of crop landraces along an elevational gradient in a major diversity center, and provide a foundation for exploring the genetic basis of local adaptation. While we cannot rule out the role of neutral evolutionary forces in the patterns we have identified, combining whole transcriptome sequencing technologies, established bioinformatics techniques, and common garden experimentation can powerfully elucidate structure of adaptive diversity across a varied landscape. Ultimately, gaining such understanding can facilitate the conservation and strategic utilization of crop genetic diversity in a time of climate change.


3.
- Artículo con arbitraje
Climate change and the transgenic adaptation strategy: smallholder livelihoods, climate justice, and maize landraces in Mexico
Mercer, Kristin L. ; Perales Rivera, Hugo Rafael (coaut.) ; Wainwright, Joel D. (coaut.) ;
Contenido en: Global Environmental Change Vol. 22, no. 2 (May 1, 2012), p. 495-504 ISSN: 0959-3780
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Climate change will affect agricultural production by subsistence farms in crop centers of origin, where landraces are conserved in situ. Various strategies for adaptation to climate change have been proposed. In this paper we examine the prospects of what we call the ‘transgenic adaptation strategy’, i.e. the appeal to use transgenic seeds to adapt to climate change, through the lens of smallholder maize farming in Mexico. Landraces are the bedrock of maize production in Mexico. We consider how maize farmers may respond to climate change and the effects of those responses on crop diversity. In this paper, we argue that the promotion of the transgenic adaptation strategy is problematic for biological and social reasons. Smallholder livelihoods in southern Mexico could suffer a disproportionate negative impact if transgenic technology is privileged as a response to climate change. Agroecological and evolutionary approaches to addressing the effects of climate change on smallholder agriculture provides an alternative adaptive strategy.


4.
Artículo
Evolutionary response of landraces to climate change in centers of crop diversity
Mercer, Kristin L. ; Perales Rivera, Hugo Rafael (coaut.) ; Marina Fernández, Carlos Félix (coaut.) ;
Contenido en: Evolutionary Applications Vol. 3, no. 5-6 (September 2010), p. 480–493 ISSN: 1752-4571
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Landraces cultivated in centers of crop diversity result from past and contemporary patterns of natural and farmer-mediated evolutionary forces. Successful in situ conservation of crop genetic resources depends on continuity of these evolutionary processes. Climate change is projected to affect agricultural production, yet analyses of impacts on in situ conservation of crop genetic diversity and farmers who conserve it have been absent. How will crop landraces respond to alterations in climate? We review the roles that phenotypic plasticity, evolution, and gene flow might play in sustaining production, although we might expect erosion of genetic diversity if landrace populations or entire races lose productivity. For example, highland maize landraces in southern Mexico do not express the plasticity necessary to sustain productivity under climate change, but may evolve in response to altered conditions. The outcome for any given crop in a given region will depend on the distribution of genetic variation that affects fitness and patterns of climate change. Understanding patterns of neutral and adaptive diversity from the population to the landscape scale is essential to clarify how landraces conserved in situ will continue to evolve and how to minimize genetic erosion of this essential natural resource.


5.
- Artículo con arbitraje
Asymmetrical local adaptation of maize landraces along an altitudinal gradient
Mercer, Kristin L. ; Martínez Vázquez, Ángel (coaut.) ; Perales Rivera, Hugo Rafael (coaut.) ;
Contenido en: Evolutionary Applications Vol. 1, no. 3 (August 2008), p. 489-500 ISSN: 1752-4571
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Crop landraces are managed populations that evolve in response to gene flow and selection. Cross-pollination among fields, seed sharing by farmers, and selection by management and environmental conditions play roles in shaping crop characteristics. We used common gardens to explore the local adaptation of maize (Zea mays ssp. mays) landrace populations from Chiapas, Mexico to altitude. We sowed seeds of 21 populations from three altitudinal ranges in two common gardens and measured two characteristics that estimate fitness: likelihood of producing good quality seed and the total mass of good quality seed per plant. The probability of lowland plants producing good quality seed was invariably high regardless of garden, while highland landraces were especially sensitive to altitude. Their likelihood of producing good seed quadrupled in the highland site. The mass of good quality seed showed a different pattern, with lowland landraces producing 25% less seed mass than the other types at high elevations. Combining these two measures of fitness revealed that the highland landraces were clearly adapted to highland sites, while lowland and midland landraces appear more adapted to the midland site. We discuss this asymmetry in local adaptation in light of climate change and in situ conservation of crop genetic resources.