Dynamic conservation of variability:  responses of wheat populations  to different selective forces  including powdery mildew

Boulc'h, V. Le; David, JL; Brabant, P.; Vallavieille‐Pope, C. de

doi:10.1051/gse:19940715

Cited by 7 publications

(9 citation statements)

References 1 publication

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“…In agreement with previous studies (Allard 1988;Le Boulc'h et al 1994;Goldringer et al 2006), we found that earliness is a major target trait for selection, the evolved population flowering earlier than the initial one. A fast response to selection is expected given the large initial genetic variability and high heritability of earliness.…”

Section: Discussionsupporting

confidence: 81%

Efficiently Tracking Selection in a Multiparental Population: The Case of Earliness in Wheat

Thepot

Restoux

Goldringer³

et al. 2014

Genetics

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Multiparental populations are innovative tools for fine mapping large numbers of loci. Here we explored the application of a wheat Multiparent Advanced Generation Inter-Cross (MAGIC) population for QTL mapping. This population was created by 12 generations of free recombination among 60 founder lines, following modification of the mating system from strict selfing to strict outcrossing using the ms1b nuclear male sterility gene. Available parents and a subset of 380 SSD lines of the resulting MAGIC population were phenotyped for earliness and genotyped with the 9K i-Select SNP array and additional markers in candidate genes controlling heading date. We demonstrated that 12 generations of strict outcrossing rapidly and drastically reduced linkage disequilibrium to very low levels even at short map distances and also greatly reduced the population structure exhibited among the parents. We developed a Bayesian method, based on allelic frequency, to estimate the contribution of each parent in the evolved population. To detect loci under selection and estimate selective pressure, we also developed a new method comparing shifts in allelic frequency between the initial and the evolved populations due to both selection and genetic drift with expectations under drift only. This evolutionary approach allowed us to identify 26 genomic areas under selection. Using association tests between flowering time and polymorphisms, 6 of these genomic areas appeared to carry flowering time QTL, 1 of which corresponds to Ppd-D1, a major gene involved in the photoperiod sensitivity. Frequency shifts at 4 of 6 areas were consistent with earlier flowering of the evolved population relative to the initial population. The use of this new outcrossing wheat population, mixing numerous initial parental lines through multiple generations of panmixia, is discussed in terms of power to detect genes under selection and association mapping. Furthermore we provide new statistical methods for use in future analyses of multiparental populations.KEYWORDS QTL detection; parental contribution; recombinant population; selection detection; experimental evolution; multiparental populations; Multiparent Advanced Generation Inter-Cross (MAGIC); MPPA LTHOUGH the recent development of genome sequencing in crop species has strongly increased capacity for gene discovery, the accurate mapping of genes controlling the genetic variation of complex traits (QTL) remains a key objective. The principal mapping methods rely on the detection of statistical association between polymorphisms at molecular markers and quantitative variation of phenotypic traits and were historically developed for progenies of biparental crosses with parents chosen for their extreme phenotypes at a trait of interest. These populations are powerful resources for QTL detection, but have low precision as few effective meioses (and thus subsequent recombinations) occur during their development. As a result, large parental haplotype blocks are preserved in the segregating population. In a...

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Section: Discussionsupporting

confidence: 81%

Efficiently Tracking Selection in a Multiparental Population: The Case of Earliness in Wheat

Thepot

Restoux

Goldringer³

et al. 2014

Genetics

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“…Cultivar mixtures have been primarily considered as a means of preserving resistance, either by enhancing the durability of race‐specific resistance genes (Wolfe, 1984; Wolfe, 1985) or by providing a dynamic way to manage genetic resources (Allard, 1990; Reinhold et al ., 1990; Balfourier et al ., 1994; Le Boulc’h et al ., 1994). Enhancing the durability of disease resistance is also a problem in pathosystems which do not comply with the theoretical criteria for success of genotype mixtures, such as those involving broadleaved plants with total or partial resistance.…”

Section: Introductionmentioning

confidence: 99%

Development of natural late blight epidemics in pure and mixed plots of potato cultivars with different levels of partial resistance

Andrivon¹,

Lucas²,

Ellissèche

2003

Plant Pathology

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Late blight, caused by Phytophthora infestans , is the most severe disease of potato worldwide. Controlling late blight epidemics is difficult, and resistance of host cultivars is either not effective enough, or too easily overcome by the pathogen to be used alone. In field trials conducted for 3 years under natural epidemics, late blight severity was significantly lower in a susceptible cultivar growing in rows alternating with partially resistant cultivars (mixtures) than in unmixed plots of the susceptible cultivar alone. Partially resistant cultivars behaved similarly in unmixed and mixed plots. Mixtures of cultivars reduced disease progress rates and sometimes delayed disease onset over unmixed plots, but did so significantly only for the slowest epidemic. This suggests that reduction of area under the disease progress curve (AUDPC) in mixtures resulted from the cumulative action of minor effects. Disease distribution was focal in all plots at all dates, as shown by Morisita's index values significantly exceeding 1. Significant yield increases for the susceptible cultivar, and occasionally for the partially resistant ones, were observed in mixed-cultivar plots compared with single-cultivar plots. These results show that cultivar mixtures can significantly reduce natural, polycyclic epidemics in broadleaved plants attacked by pathogens causing rapidly expanding lesions.

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“…This conservation strategy provides a natural laboratory for evolution to continue and helps a gradual buildup of traits imparting adaptation to specific eco-geographical regions and those matching the requirements of farmers, local communities and populations to continue. Several authorities indicated that the need for on-farm conservation of landraces is one of the most important recent questions in plant genetic resources management (Le Boulch et al, 1994;Kebebew et al, 2001). Farmers continue to grow and maintain a wheat landrace if it meets their production and consumption needs.…”

Section: Conservation and Utilization Of Wheat Landracesmentioning

confidence: 99%

“…However, for individual farmers, private values of a landrace are the main motivating factors for growing landraces as a source of income and a means of survival. Therefore, ex situ conservation in a genebank may be the only practical option to conserve landraces having low private but high public value (Le Boulch et al, 1994).…”

Section: Conservation and Utilization Of Wheat Landracesmentioning

confidence: 99%

Wheat Landraces: A mini review <br>

Jaradat

2013

Emir. J. Food Agric

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Traditional farmers planted diverse assemblages of wheat landraces to lower the risk of failure and increase food security because they had limited capacity to control the spatially heterogeneous and temporally unpredictable environments. This practice led to the development of landrace meta-populations of wheat and the emergence of farmers' seed systems through which they accessed and exchanged diverse genetic material. During the last ~50 years, the introduction of high-yielding wheat varieties into, and the structural changes in wheat farming systems in developing countries, led to the loss of genetic diversity and fragmentation of metapopulation structures of wheat landraces from large parts of the Fertile Crescent, the center of origin and diversity of wheat landraces. However, the persistence cultivation of some wheat landraces attests to their continued value to farmers, or to their competitive agronomic or nutritional advantage relative to modern varieties. For farmers to continue to grow, select, and manage local wheat landraces, and to reverse the fragmentation of their meta-populations, especially in their center of diversity, and allow evolutionary processes that mold landrace diversity to continue, their value should be raised to approximate or exceed the social value of high-yielding wheat varieties. This review provides information on wheat domestication and the origin of wheat landraces; their dynamic on-farm conservation and utilization in improving modern wheat cultivars and reversing the genetic erosion of wheat genetic diversity.

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Dynamic conservation of variability: responses of wheat populations to different selective forces including powdery mildew

Cited by 7 publications

References 1 publication

Efficiently Tracking Selection in a Multiparental Population: The Case of Earliness in Wheat

Efficiently Tracking Selection in a Multiparental Population: The Case of Earliness in Wheat

Development of natural late blight epidemics in pure and mixed plots of potato cultivars with different levels of partial resistance

Wheat Landraces: A mini review <br>

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