One potential legacy of the widespread deforestation of the 1700-1800s and subsequent agricultura... more One potential legacy of the widespread deforestation of the 1700-1800s and subsequent agricultural abandonment and reforestation across the eastern United States (U.S.) during the 1900s is the establishment of introduced apple trees (Malus domestica) exclusive of naturally occurring native crab apple species. As these apple trees might provide ecological services and a genetic reserve of long-forgotten apple cultivars, a region-wide forest inventory was used to estimate the current extent, condition, and changes in the population of apple trees across eastern forests of the U.S. It was found that hundreds of millions of apple trees currently exist in the forests of the northern U.S. with indications of population senescence as the abundance of seedlings and saplings decline while the abundance of the largest-sized trees and standing dead trees increase. The distribution of forest apple trees is only aligned with native crab apple distributions in limited areas, suggesting distinct feral apple populations derived from agricultural abandonment decades ago. As these extant apple trees are likely relics of former orchards and/or their naturally dispersed progeny, these populations may serve as an in-situ gene bank representing hundreds, if not thousands, of apple cultivars forgotten long ago but adapted to local conditions and perhaps of importance to ensuring the future resilience of domestic apple production in the context of global change.
The USDA-ARS National Plant Germplasm System (NPGS) apple collection in Geneva, NY, USA maintains... more The USDA-ARS National Plant Germplasm System (NPGS) apple collection in Geneva, NY, USA maintains accessions of the primary Malus domestica (Suckow) Borkh. progenitor species M. sieversii (Ledeb.) M. Roem., M. orientalis Uglitzk., and M. sylvestris (L.) Mill. Many of these accessions originated from seeds that were collected from wild populations in the species’ centers of diversity. Some of these accessions have fruit phenotypes that suggest recent M. domestica hybridization, which if true would represent crop contamination of wild species populations and mislabeled species status of NPGS accessions. Pedigree connections and admixture between M. domestica and its progenitor species can be readily identified with apple SNP array data, despite such arrays not being designed for these purposes. To investigate species purity, most (463 accessions) of the NPGS accessions labeled as these three progenitor species were genotyped using the 20K apple SNP array. DNA profiles obtained were co...
Societal Impact StatementHistoric North American apple (Malus domestica) orchards that thrived in... more Societal Impact StatementHistoric North American apple (Malus domestica) orchards that thrived in the late 19th and early 20th centuries, with cultivar compositions unlike today's orchards, are vanishing. There are several reasons for this loss: tree aging, cost of tree maintenance, and urbanization. Many groups have collected local knowledge regarding the history and horticulture of apples using both phenotypic and genotypic identification methods. Some of these groups have joined with scientists to form the collaborative “Historic Fruit Tree Working Group of North America” to facilitate the conservation of heirloom apple cultivars in North America through documentation, identification, collaboration, and education.
Peach and nectarine production worldwide is increasing; however consumption is flat or declining ... more Peach and nectarine production worldwide is increasing; however consumption is flat or declining because of the inconsistent eating quality experienced by consumers. The main factor for this inconsistent quality is mealiness or woolliness, a form of chilling injury that develops following shipping periods in the global fruit market today. Our research groups have devised various postharvest methods to prolong storage life, including controlled atmosphere and delayed storage; however, these treatments only delay mealiness. Mealiness texture results from disruption of the normal ripening process involving disassembly of cell wall material, and creates a soft fruit texture that is dry and grainy instead of juicy and smooth. Solving this problem is a prerequisite for increasing the demand for fresh peach and nectarine. Two approaches were used to reveal genes and their associated biochemical processes that can confer resistance to mealiness or wooliness. At the Volcani Center, Israel, a nectarine cultivar and the peach cultivar (isogenetic materials) from which the nectarine cultivar spontaneously arose, and at the Kearney Agricultural Center of UC Davis, USA, a peach population that segregates for quantitative resistance to mealiness was used for dissecting the genetic components of mealiness development. During our project we have conducted research integrating the information from phenotypic, biochemical and gene expression studies, proposed possible candidate genes and SNPs-QTLs mapping that are involved in reducing peach mealiness susceptibility. Numerous genes related to ethylene biosynthesis and its signal transduction, cell wall structure and metabolism, stress response, different transcription factor families were detected as being differentially accumulated in the cold-treated samples of these sensitive and less sensitive genotypes. The ability to produce ethylene and keep active genes involved in ethylene signaling, GTP-binding protein, EIN-3 binding protein and an ethylene receptor and activation of ethyleneresponsive fruit ripening genes during cold storage provided greater resistance to CI. Interestingly, in the functional category of genes differentially expressed at harvest, less chilling sensitive cultivar had more genes in categories related to antioxidant and heat sock proteins/chaperones that may help fruit to adapt to low temperature stress. The specific objectives of the proposed research were to: characterize the phenotypes and cell wall components of the two resistant systems in response to mealiness- inducing conditions; identify commonalities and specific differences in cell wall proteins and the transcriptome that are associated with low mealiness incidence; integrate the information from phenotypic, biochemical, and gene expression studies to identify candidate genes that are involved in reducing mealiness susceptibility; locate these genes in the Prunus genome; and associate the genes with genomic regions conferring quantitative genetic variation for mealiness resistance. By doing this we will locate genetic markers for mealiness development, essential tools for selection of mealiness resistant peach lines with improved fruit storability and quality. In our research, QTLs have been located in our peach SNPs map, and proposed candidate genes obtained from the integrated result of phenotypic, biochemical and gene expression analysis are being identified in our QTLs as an approach searching for consistent assistant markers for peach breeding programs.
One potential legacy of the widespread deforestation of the 1700-1800s and subsequent agricultura... more One potential legacy of the widespread deforestation of the 1700-1800s and subsequent agricultural abandonment and reforestation across the eastern United States (U.S.) during the 1900s is the establishment of introduced apple trees (Malus domestica) exclusive of naturally occurring native crab apple species. As these apple trees might provide ecological services and a genetic reserve of long-forgotten apple cultivars, a region-wide forest inventory was used to estimate the current extent, condition, and changes in the population of apple trees across eastern forests of the U.S. It was found that hundreds of millions of apple trees currently exist in the forests of the northern U.S. with indications of population senescence as the abundance of seedlings and saplings decline while the abundance of the largest-sized trees and standing dead trees increase. The distribution of forest apple trees is only aligned with native crab apple distributions in limited areas, suggesting distinct feral apple populations derived from agricultural abandonment decades ago. As these extant apple trees are likely relics of former orchards and/or their naturally dispersed progeny, these populations may serve as an in-situ gene bank representing hundreds, if not thousands, of apple cultivars forgotten long ago but adapted to local conditions and perhaps of importance to ensuring the future resilience of domestic apple production in the context of global change.
The USDA-ARS National Plant Germplasm System (NPGS) apple collection in Geneva, NY, USA maintains... more The USDA-ARS National Plant Germplasm System (NPGS) apple collection in Geneva, NY, USA maintains accessions of the primary Malus domestica (Suckow) Borkh. progenitor species M. sieversii (Ledeb.) M. Roem., M. orientalis Uglitzk., and M. sylvestris (L.) Mill. Many of these accessions originated from seeds that were collected from wild populations in the species’ centers of diversity. Some of these accessions have fruit phenotypes that suggest recent M. domestica hybridization, which if true would represent crop contamination of wild species populations and mislabeled species status of NPGS accessions. Pedigree connections and admixture between M. domestica and its progenitor species can be readily identified with apple SNP array data, despite such arrays not being designed for these purposes. To investigate species purity, most (463 accessions) of the NPGS accessions labeled as these three progenitor species were genotyped using the 20K apple SNP array. DNA profiles obtained were co...
Societal Impact StatementHistoric North American apple (Malus domestica) orchards that thrived in... more Societal Impact StatementHistoric North American apple (Malus domestica) orchards that thrived in the late 19th and early 20th centuries, with cultivar compositions unlike today's orchards, are vanishing. There are several reasons for this loss: tree aging, cost of tree maintenance, and urbanization. Many groups have collected local knowledge regarding the history and horticulture of apples using both phenotypic and genotypic identification methods. Some of these groups have joined with scientists to form the collaborative “Historic Fruit Tree Working Group of North America” to facilitate the conservation of heirloom apple cultivars in North America through documentation, identification, collaboration, and education.
Peach and nectarine production worldwide is increasing; however consumption is flat or declining ... more Peach and nectarine production worldwide is increasing; however consumption is flat or declining because of the inconsistent eating quality experienced by consumers. The main factor for this inconsistent quality is mealiness or woolliness, a form of chilling injury that develops following shipping periods in the global fruit market today. Our research groups have devised various postharvest methods to prolong storage life, including controlled atmosphere and delayed storage; however, these treatments only delay mealiness. Mealiness texture results from disruption of the normal ripening process involving disassembly of cell wall material, and creates a soft fruit texture that is dry and grainy instead of juicy and smooth. Solving this problem is a prerequisite for increasing the demand for fresh peach and nectarine. Two approaches were used to reveal genes and their associated biochemical processes that can confer resistance to mealiness or wooliness. At the Volcani Center, Israel, a nectarine cultivar and the peach cultivar (isogenetic materials) from which the nectarine cultivar spontaneously arose, and at the Kearney Agricultural Center of UC Davis, USA, a peach population that segregates for quantitative resistance to mealiness was used for dissecting the genetic components of mealiness development. During our project we have conducted research integrating the information from phenotypic, biochemical and gene expression studies, proposed possible candidate genes and SNPs-QTLs mapping that are involved in reducing peach mealiness susceptibility. Numerous genes related to ethylene biosynthesis and its signal transduction, cell wall structure and metabolism, stress response, different transcription factor families were detected as being differentially accumulated in the cold-treated samples of these sensitive and less sensitive genotypes. The ability to produce ethylene and keep active genes involved in ethylene signaling, GTP-binding protein, EIN-3 binding protein and an ethylene receptor and activation of ethyleneresponsive fruit ripening genes during cold storage provided greater resistance to CI. Interestingly, in the functional category of genes differentially expressed at harvest, less chilling sensitive cultivar had more genes in categories related to antioxidant and heat sock proteins/chaperones that may help fruit to adapt to low temperature stress. The specific objectives of the proposed research were to: characterize the phenotypes and cell wall components of the two resistant systems in response to mealiness- inducing conditions; identify commonalities and specific differences in cell wall proteins and the transcriptome that are associated with low mealiness incidence; integrate the information from phenotypic, biochemical, and gene expression studies to identify candidate genes that are involved in reducing mealiness susceptibility; locate these genes in the Prunus genome; and associate the genes with genomic regions conferring quantitative genetic variation for mealiness resistance. By doing this we will locate genetic markers for mealiness development, essential tools for selection of mealiness resistant peach lines with improved fruit storability and quality. In our research, QTLs have been located in our peach SNPs map, and proposed candidate genes obtained from the integrated result of phenotypic, biochemical and gene expression analysis are being identified in our QTLs as an approach searching for consistent assistant markers for peach breeding programs.
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Papers by Cameron Peace