Differences were observed both within and between strawberry cultivars in the relative importance... more Differences were observed both within and between strawberry cultivars in the relative importance of yield components. Most cultivars had high coefficients among yield, crown density at harvest, and fruit number/crown, but there was variation among cultivars in the coefficients between yield and fruit weight.
The strawberry (Fragaria X ananassa L.) ‘Midway’ and ‘Guardian’ were grown runnerless at several ... more The strawberry (Fragaria X ananassa L.) ‘Midway’ and ‘Guardian’ were grown runnerless at several within-row spacings (8-47 cm). The proportion of dry matter allocated to fruit was negatively correlated with spacing distance for ‘Guardian’ (r = 0.68), but positively correlated for ‘Midway’ (r = 0.91). Total crown weight was positively associated with plant-spacing distance for ‘Guardian’ (r = 0.88) but not for ‘Midway’ (r = 0.05). Specific leaf weight was positively correlated with spacing for both cultivars.
Among the most distantly separated plant species are those that are found on the polar regions of... more Among the most distantly separated plant species are those that are found on the polar regions of the northern and southern hemispheres, the so-called bipolar species. Two routes of introduction have been proposed—long-distance dispersal (LDD) and mountain hopping (MH). Shorebirds have been implicated in the distribution of the bipolar species by several authors, but the most likely participants and the most probable routes of introduction have been little investigated. The Global Biodiversity Information Facility database was accessed to determine the geographic range of those angiosperm species that have been reported to have bipolar distributions. A bipolar plant species was considered most likely to have been dispersed by LDD if it has a distinct disjunct distribution between North and South America, and through MH if it is found in intermediate latitudes. The Atlas of Bird Migrations and the Cornell Birds of the World database were searched to discover which birds make long-dis...
Reducing crop losses due to abiotic stresses is a major target of agricultural biotechnology that... more Reducing crop losses due to abiotic stresses is a major target of agricultural biotechnology that will increase with climate change and global population growth. Concerns, however, have been raised about potential ecological impacts if transgenes become established in wild populations and cause increased competitiveness of weedy or invasive species. Potential risks will be a function of transgene movement, population sizes, and fitness effects on the recipient population. While key components influencing gene flow have been extensively investigated, there have been few studies on factors subsequent to transgene movement that can influence persistence and competitiveness. Here, we performed multiyear, multigenerational, assessment to examine fitness effects and persistence of three mechanistically different abiotic stress tolerance genes: and . Transgenic overexpressing these genes were grown in pure populations and in competition with wild-type (WT) parents for six generations spann...
A linkage mapping approach was used to identify quantitative trait loci (QTL) associated with day... more A linkage mapping approach was used to identify quantitative trait loci (QTL) associated with day‐neutrality in the commercial strawberry, Fragaria × ananassa (Duch ex Rozier). Amplified Fragment Length Polymorphism (AFLP) markers were used to build a genetic map with a population of 127 lines developed by crossing the day‐neutral (DN) ‘Tribute’ with the short‐day (SD) ‘Honeoye’. The population was genotyped with AFLP markers and 429 single dose restriction fragments (SDRF) were placed on a consensus map of 1541 cM with 43 linkage groups. Individuals from the mapping population were observed for their flowering habit throughout the growing season in Michigan (MI), Minnesota (MN), Maryland (MD), Oregon (OR) and California (CA). Eight QTL were found that were either location specific or shared among locations. None of these QTL explained >36% of the phenotypic variation, indicating that the inheritance of day‐neutrality is likely a polygenic trait.
Starch gel electrophoresis was used to fingerprint 55 Taxus plants, listed as 21 species and/or c... more Starch gel electrophoresis was used to fingerprint 55 Taxus plants, listed as 21 species and/or cultivars. Plants were analyzed for six enzymes, representing eight putative loci. Within many of the cultivars, different fingerprints were observed, indicating nomenclatural errors in Taxus.
Seven highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for their photosynthe... more Seven highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for their photosynthetic heat stability. Ail showed significant reductions in CO2 assimilation rates (A) as leaf temperatures were raised from 20 to 30C, although `Blue-crop', `Jersey', `Elliot', and `Rubel' (22% to - 27%) were significantly less affected than…
The commercial strawberry Frageria × ananassa and several clones of F. chiloensis and F. virginia... more The commercial strawberry Frageria × ananassa and several clones of F. chiloensis and F. virginiana were preconditioned in growth chambers under the following conditions: 500 μmol m-7s-1 PAR and 20° day, 10° night or 30° day and 20° night. After at least 3 weeks of preconditioning at the two different temperature regimes, leaf photosynthetic rate (A) was determined for temperatures ranging from 10 to 35° in 2-3° increments with an open gas exchange system under laboratory conditions. The objective was to determine if F. virginiana and F. × ananassa can photosynthesize at higher temperatures than F. chiloensis, and if any of these would acclimate to higher temperatures. F. chiloensis did not acclimate to higher temperatures, and bad maximum A between 16 and 20°. F. virginiana did acclimate to higher temperatures, with maximum A for the low temp treatment between 18 and 24°, and for the high temp treatment between 24 and 30°. The commercial cultivars of `Earliglow' and `Redchief&#...
To determine if blueberry shoestring virus (BBSSV) is absent in the southern United States due to... more To determine if blueberry shoestring virus (BBSSV) is absent in the southern United States due to resistance of cultivars, we mechanically and rub-inoculated 1-year-old rooted microshoots of nine cultivars representing southern rabbiteye (Vaccinium ashei Reade), southern highbush (hybrids of V. corymbosum and V. darrowi Camp), and northern highbush (V. corymbosum L.). Leaves were sampled from plants, and enzyme-linked immunosorbent assay screened for the presence of virus over 15 months. Only a few individuals were infected after aphid inoculation, but many northern and southern cultivars became infected after mechanical inoculation. Northern highbush `Elliot' (50%) and `Blueray' (46.3%) had the highest infection rates, followed by rabbiteye `Climax' (36.3%) and the southern highbush `O'Neal' (12.5%). The lowest rates of infection were found in southern highbush `Georgiagem' (2.5%), `Misty' (2.5%), rabbiteye `Brightwell' (0.0%), and northern highbush ...
Flower bud and leaf samples collected from a wide range of native North American Vaccinium popula... more Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.
The next wave of genetically engineered crops will use genes that modify gene regulation, plant m... more The next wave of genetically engineered crops will use genes that modify gene regulation, plant metabolism, or signal transduction. The potential for these genes to have cascading effects on metabolism, physiology, and development increases the possibility for unintended effects that influence crop performance or environmental impact. This review examines altered ethylene signaling as an example of a complex trait with many horticultural applications. Genes for modified ethylene production or perception intended to regulate ripening, senescence, or stress or disease resistance have been observed to cause a broad range of secondary effects, including modified growth and development and increased severity to biotic and abiotic stresses. Successful use of complex traits in crop varieties will frequently require methods to reduce secondary effects, including the use of targeted gene expression. Risk assessment will need to consider observed pleiotropic effects on fitness within the cont...
Differences were observed both within and between strawberry cultivars in the relative importance... more Differences were observed both within and between strawberry cultivars in the relative importance of yield components. Most cultivars had high coefficients among yield, crown density at harvest, and fruit number/crown, but there was variation among cultivars in the coefficients between yield and fruit weight.
The strawberry (Fragaria X ananassa L.) ‘Midway’ and ‘Guardian’ were grown runnerless at several ... more The strawberry (Fragaria X ananassa L.) ‘Midway’ and ‘Guardian’ were grown runnerless at several within-row spacings (8-47 cm). The proportion of dry matter allocated to fruit was negatively correlated with spacing distance for ‘Guardian’ (r = 0.68), but positively correlated for ‘Midway’ (r = 0.91). Total crown weight was positively associated with plant-spacing distance for ‘Guardian’ (r = 0.88) but not for ‘Midway’ (r = 0.05). Specific leaf weight was positively correlated with spacing for both cultivars.
Among the most distantly separated plant species are those that are found on the polar regions of... more Among the most distantly separated plant species are those that are found on the polar regions of the northern and southern hemispheres, the so-called bipolar species. Two routes of introduction have been proposed—long-distance dispersal (LDD) and mountain hopping (MH). Shorebirds have been implicated in the distribution of the bipolar species by several authors, but the most likely participants and the most probable routes of introduction have been little investigated. The Global Biodiversity Information Facility database was accessed to determine the geographic range of those angiosperm species that have been reported to have bipolar distributions. A bipolar plant species was considered most likely to have been dispersed by LDD if it has a distinct disjunct distribution between North and South America, and through MH if it is found in intermediate latitudes. The Atlas of Bird Migrations and the Cornell Birds of the World database were searched to discover which birds make long-dis...
Reducing crop losses due to abiotic stresses is a major target of agricultural biotechnology that... more Reducing crop losses due to abiotic stresses is a major target of agricultural biotechnology that will increase with climate change and global population growth. Concerns, however, have been raised about potential ecological impacts if transgenes become established in wild populations and cause increased competitiveness of weedy or invasive species. Potential risks will be a function of transgene movement, population sizes, and fitness effects on the recipient population. While key components influencing gene flow have been extensively investigated, there have been few studies on factors subsequent to transgene movement that can influence persistence and competitiveness. Here, we performed multiyear, multigenerational, assessment to examine fitness effects and persistence of three mechanistically different abiotic stress tolerance genes: and . Transgenic overexpressing these genes were grown in pure populations and in competition with wild-type (WT) parents for six generations spann...
A linkage mapping approach was used to identify quantitative trait loci (QTL) associated with day... more A linkage mapping approach was used to identify quantitative trait loci (QTL) associated with day‐neutrality in the commercial strawberry, Fragaria × ananassa (Duch ex Rozier). Amplified Fragment Length Polymorphism (AFLP) markers were used to build a genetic map with a population of 127 lines developed by crossing the day‐neutral (DN) ‘Tribute’ with the short‐day (SD) ‘Honeoye’. The population was genotyped with AFLP markers and 429 single dose restriction fragments (SDRF) were placed on a consensus map of 1541 cM with 43 linkage groups. Individuals from the mapping population were observed for their flowering habit throughout the growing season in Michigan (MI), Minnesota (MN), Maryland (MD), Oregon (OR) and California (CA). Eight QTL were found that were either location specific or shared among locations. None of these QTL explained >36% of the phenotypic variation, indicating that the inheritance of day‐neutrality is likely a polygenic trait.
Starch gel electrophoresis was used to fingerprint 55 Taxus plants, listed as 21 species and/or c... more Starch gel electrophoresis was used to fingerprint 55 Taxus plants, listed as 21 species and/or cultivars. Plants were analyzed for six enzymes, representing eight putative loci. Within many of the cultivars, different fingerprints were observed, indicating nomenclatural errors in Taxus.
Seven highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for their photosynthe... more Seven highbush blueberry (Vaccinium corymbosum L.) cultivars were evaluated for their photosynthetic heat stability. Ail showed significant reductions in CO2 assimilation rates (A) as leaf temperatures were raised from 20 to 30C, although `Blue-crop', `Jersey', `Elliot', and `Rubel' (22% to - 27%) were significantly less affected than…
The commercial strawberry Frageria × ananassa and several clones of F. chiloensis and F. virginia... more The commercial strawberry Frageria × ananassa and several clones of F. chiloensis and F. virginiana were preconditioned in growth chambers under the following conditions: 500 μmol m-7s-1 PAR and 20° day, 10° night or 30° day and 20° night. After at least 3 weeks of preconditioning at the two different temperature regimes, leaf photosynthetic rate (A) was determined for temperatures ranging from 10 to 35° in 2-3° increments with an open gas exchange system under laboratory conditions. The objective was to determine if F. virginiana and F. × ananassa can photosynthesize at higher temperatures than F. chiloensis, and if any of these would acclimate to higher temperatures. F. chiloensis did not acclimate to higher temperatures, and bad maximum A between 16 and 20°. F. virginiana did acclimate to higher temperatures, with maximum A for the low temp treatment between 18 and 24°, and for the high temp treatment between 24 and 30°. The commercial cultivars of `Earliglow' and `Redchief&#...
To determine if blueberry shoestring virus (BBSSV) is absent in the southern United States due to... more To determine if blueberry shoestring virus (BBSSV) is absent in the southern United States due to resistance of cultivars, we mechanically and rub-inoculated 1-year-old rooted microshoots of nine cultivars representing southern rabbiteye (Vaccinium ashei Reade), southern highbush (hybrids of V. corymbosum and V. darrowi Camp), and northern highbush (V. corymbosum L.). Leaves were sampled from plants, and enzyme-linked immunosorbent assay screened for the presence of virus over 15 months. Only a few individuals were infected after aphid inoculation, but many northern and southern cultivars became infected after mechanical inoculation. Northern highbush `Elliot' (50%) and `Blueray' (46.3%) had the highest infection rates, followed by rabbiteye `Climax' (36.3%) and the southern highbush `O'Neal' (12.5%). The lowest rates of infection were found in southern highbush `Georgiagem' (2.5%), `Misty' (2.5%), rabbiteye `Brightwell' (0.0%), and northern highbush ...
Flower bud and leaf samples collected from a wide range of native North American Vaccinium popula... more Flower bud and leaf samples collected from a wide range of native North American Vaccinium populations were tested for the presence of blueberry shoestring virus (BBSSV) using the enzyme-linked immunosorbant assay. The highest disease incidence was found in Michigan (14%), although a few positive samples also were found in Virginia, New Jersey, Maine, Ontario, and Quebec. Of seven species tested, only V. corymbosum L. and V. angustifolium Ait. were infected with BBSSV.
The next wave of genetically engineered crops will use genes that modify gene regulation, plant m... more The next wave of genetically engineered crops will use genes that modify gene regulation, plant metabolism, or signal transduction. The potential for these genes to have cascading effects on metabolism, physiology, and development increases the possibility for unintended effects that influence crop performance or environmental impact. This review examines altered ethylene signaling as an example of a complex trait with many horticultural applications. Genes for modified ethylene production or perception intended to regulate ripening, senescence, or stress or disease resistance have been observed to cause a broad range of secondary effects, including modified growth and development and increased severity to biotic and abiotic stresses. Successful use of complex traits in crop varieties will frequently require methods to reduce secondary effects, including the use of targeted gene expression. Risk assessment will need to consider observed pleiotropic effects on fitness within the cont...
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