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Genetic population structure of cacao plantings within a young production area in Nicaragua.

Trognitz B, Scheldeman X, Hansel-Hohl K, Kuant A, Grebe H, Hermann M - PLoS ONE (2011)

Bottom Line: This research aimed to assist local farmers to develop production of high-value cocoa based on optimal use of cacao biodiversity.Based on intermediate allelic diversity, there was large farm-to-farm multilocus genotypic variation.Of two possible strategies for future development of cacao in Waslala, i.e. introducing more unrelated germplasm, or working with existing on-site diversity, the latter seems most appropriate.

View Article: PubMed Central - PubMed

Affiliation: Austrian Institute of Technology, Seibersdorf, Austria. bodo.trognitz@ait.ac.at

ABSTRACT
Significant cocoa production in the municipality of Waslala, Nicaragua, began in 1961. Since the 1980s, its economic importance to rural smallholders increased, and the region now contributes more than 50% of national cocoa bean production. This research aimed to assist local farmers to develop production of high-value cocoa based on optimal use of cacao biodiversity. Using microsatellite markers, the allelic composition and genetic structure of cacao was assessed from 44 representative plantings and two unmanaged trees. The population at Waslala consists of only three putative founder genotype spectra (lineages). Two (B and R) were introduced during the past 50 years and occur in >95% of all trees sampled, indicating high rates of outcrossing. Based on intermediate allelic diversity, there was large farm-to-farm multilocus genotypic variation. GIS analysis revealed unequal distribution of the genotype spectra, with R being frequent within a 2 km corridor along roads, and B at more remote sites with lower precipitation. The third lineage, Y, was detected in the two forest trees. For explaining the spatial stratification of the genotype spectra, both human intervention and a combination of management and selection driven by environmental conditions, appear responsible. Genotypes of individual trees were highly diverse across plantings, thus enabling selection for farm-specific qualities. On-farm populations can currently be most clearly recognized by the degree of the contribution of the three genotype spectra. Of two possible strategies for future development of cacao in Waslala, i.e. introducing more unrelated germplasm, or working with existing on-site diversity, the latter seems most appropriate. Superior genotypes could be selected by their specific composite genotype spectra as soon as associations with desired quality traits are established, and clonally multiplied. The two Y trees from the forest share a single multilocus genotype, possibly representing the Mayan, 'ancient Criollo' cacao.

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Related in: MedlinePlus

Map of Waslala municipality in central northern Nicaragua.Pie diagrams represent individual smallholder farms and the shares of putative founder genotype spectra, B, R, and Y, totalled over all cacao trees sampled.
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pone-0016056-g005: Map of Waslala municipality in central northern Nicaragua.Pie diagrams represent individual smallholder farms and the shares of putative founder genotype spectra, B, R, and Y, totalled over all cacao trees sampled.

Mentions: As a measure of relatedness between different farms by genotype spectra composition, the average genetic distance over all 15 marker loci quantified by Shannon's index was applied. The results are summarized via principal coordinates analysis in Figure 4. Except FBBSB, the two orphan trees W041 and W042 near the forest, most farms were not well separated from each other by this method. This reflects the genetic composition of farms; with every farm having trees possessing genotypes of various states of admixture, considering the lineages as detected by the Structure program. That is illustrated by the pie diagrams on the map of Waslala municipality (Figure 5), each pie plot representing the proportion of the three genotype lineages contributing to an individual farm. The majority of farms are represented by tree genotypes made up of two (B and R) or three (B, R, and Y) lineages. Only a few farms consist of nearly exclusively B genotype spectrum partitions, and only the closely spaced south-eastern plantings F083 and F084, both owned by the same single farmer, contain nearly pure B lineage trees (Figure 5).


Genetic population structure of cacao plantings within a young production area in Nicaragua.

Trognitz B, Scheldeman X, Hansel-Hohl K, Kuant A, Grebe H, Hermann M - PLoS ONE (2011)

Map of Waslala municipality in central northern Nicaragua.Pie diagrams represent individual smallholder farms and the shares of putative founder genotype spectra, B, R, and Y, totalled over all cacao trees sampled.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3021531&req=5

pone-0016056-g005: Map of Waslala municipality in central northern Nicaragua.Pie diagrams represent individual smallholder farms and the shares of putative founder genotype spectra, B, R, and Y, totalled over all cacao trees sampled.
Mentions: As a measure of relatedness between different farms by genotype spectra composition, the average genetic distance over all 15 marker loci quantified by Shannon's index was applied. The results are summarized via principal coordinates analysis in Figure 4. Except FBBSB, the two orphan trees W041 and W042 near the forest, most farms were not well separated from each other by this method. This reflects the genetic composition of farms; with every farm having trees possessing genotypes of various states of admixture, considering the lineages as detected by the Structure program. That is illustrated by the pie diagrams on the map of Waslala municipality (Figure 5), each pie plot representing the proportion of the three genotype lineages contributing to an individual farm. The majority of farms are represented by tree genotypes made up of two (B and R) or three (B, R, and Y) lineages. Only a few farms consist of nearly exclusively B genotype spectrum partitions, and only the closely spaced south-eastern plantings F083 and F084, both owned by the same single farmer, contain nearly pure B lineage trees (Figure 5).

Bottom Line: This research aimed to assist local farmers to develop production of high-value cocoa based on optimal use of cacao biodiversity.Based on intermediate allelic diversity, there was large farm-to-farm multilocus genotypic variation.Of two possible strategies for future development of cacao in Waslala, i.e. introducing more unrelated germplasm, or working with existing on-site diversity, the latter seems most appropriate.

View Article: PubMed Central - PubMed

Affiliation: Austrian Institute of Technology, Seibersdorf, Austria. bodo.trognitz@ait.ac.at

ABSTRACT
Significant cocoa production in the municipality of Waslala, Nicaragua, began in 1961. Since the 1980s, its economic importance to rural smallholders increased, and the region now contributes more than 50% of national cocoa bean production. This research aimed to assist local farmers to develop production of high-value cocoa based on optimal use of cacao biodiversity. Using microsatellite markers, the allelic composition and genetic structure of cacao was assessed from 44 representative plantings and two unmanaged trees. The population at Waslala consists of only three putative founder genotype spectra (lineages). Two (B and R) were introduced during the past 50 years and occur in >95% of all trees sampled, indicating high rates of outcrossing. Based on intermediate allelic diversity, there was large farm-to-farm multilocus genotypic variation. GIS analysis revealed unequal distribution of the genotype spectra, with R being frequent within a 2 km corridor along roads, and B at more remote sites with lower precipitation. The third lineage, Y, was detected in the two forest trees. For explaining the spatial stratification of the genotype spectra, both human intervention and a combination of management and selection driven by environmental conditions, appear responsible. Genotypes of individual trees were highly diverse across plantings, thus enabling selection for farm-specific qualities. On-farm populations can currently be most clearly recognized by the degree of the contribution of the three genotype spectra. Of two possible strategies for future development of cacao in Waslala, i.e. introducing more unrelated germplasm, or working with existing on-site diversity, the latter seems most appropriate. Superior genotypes could be selected by their specific composite genotype spectra as soon as associations with desired quality traits are established, and clonally multiplied. The two Y trees from the forest share a single multilocus genotype, possibly representing the Mayan, 'ancient Criollo' cacao.

Show MeSH
Related in: MedlinePlus