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Li Lu, Kirk W. Pomper, Jeremiah D. Lowe and Sheri B. Crabtree

( Pomper et al., 2003 )], and SSR ( Pomper et al., 2010 ). Overall, these studies determined that the genetic variation in both cultivated and wild pawpaws is similar to those of other long-lived, temperate woody perennials characterized by a widespread

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Chalita Sriladda, Heidi A. Kratsch, Steven R. Larson and Roger K. Kjelgren

genetic variation and correlation analysis. Genetic analysis. Leaf samples (two to three leaves per plant) collected from each field population (12 plants per population) were dried in 28 to 200 mesh silica gel (Fisher Scientific, Pittsburgh, PA). DNA was

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Jaejoon Kim and David J. Wolyn

conditions. Effective breeding requires both genetic variation and heritability for attributes of interest. Therefore, the objectives of this study were to assess variation for biochemical and physiological parameters associated with freezing tolerance in

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Ryan J. Hayes and Yong-Biao Liu

variation within lettuce for shelf life are needed. The objectives of this research were to determine the genetic variation for shelf life of salad-cut lettuce in low-O 2 MA environments and to develop rapid evaluation methods suitable for a lettuce

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Nathan C. Phillips, Steven R. Larson and Daniel T. Drost

( Adair et al., 2006 ; Hellier, 2000 ). Growers depending on wild seed collection would benefit from understanding genetic variation in wild populations across the natural landscape. Knowing the extent of genetic diversity within and among populations

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Peter J. Zale, Daniel K. Struve, Pablo Jourdan and David M. Francis

were grown in a container nursery and examine genetic variation in the population to help guide decisions regarding plant selection and cultivar development. Materials and Methods A breeding population was derived from seed collected from 30

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Ruby Valdez-Ojeda, José Luis Hernández-Stefanoni, Margarita Aguilar-Espinosa, Renata Rivera-Madrid, Rodomiro Ortiz and Carlos F. Quiros

grouped all individuals from Cooperativa and Cluster II grouped all those from Yaxcaba. According to similarity distances, both clusters exhibited high genetic variation: Cluster I exhibited the highest genetic variation (0.14815 to 0.8679) compared with

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Kanin J. Routson, Gayle M. Volk, Christopher M. Richards, Steven E. Smith, Gary Paul Nabhan and Victoria Wyllie de Echeverria

), except that fewer polymorphic alleles were identified in M. fusca than either M. sieversii ( Richards et al., 2009 ) or M. orientalis Uglitzk. ( Volk et al., 2008 ). This may indicate a lower total genetic variation in M. fusca compared with other

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Fenny Dane, Leigh K. Hawkins and Hongwen Huang

Genetic variation among nine populations of Ozark chinkapin [Castanea pumila (L.) Mill. var. ozarkensis (Ashe) Tucker], threatened by their susceptibility to chestnut blight (Cryphonectria parasitica (Murrill) Barr), was investigated. Population genetic parameters estimated from isozyme variation suggest the populations have a higher genetic diversity (He = 0.227) than populations of the other Castanea Mill. species on the North American continent, the American chestnut (C. dentata (Marsh.) Borkh.) High levels of heterozygosity were detected within the populations, but nonsignificant differences in genetic diversity were observed among the different populations. Principal component analysis based on isozyme allele frequencies or randomly amplified polymorphic DNA phenotype frequencies showed clustering of the same populations. Populations with high levels of genetic diversity and unusual alleles should be the focal point of conservation biologists for capturing much of the genetic variation of the species.

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Beiquan Mou

There is increasing medical evidence for the health benefits derived from dietary intake of carotenoid antioxidants, such as β-carotene and lutein. Enhancing the nutritional levels of vegetables would improve the nutrient intake without requiring an increase in consumption. A breeding program to improve the nutritional quality of lettuce (Lactuca sativa L.) must start with an assessment of the existing genetic variation. To assess the genetic variability in carotenoid contents, 52 genotypes including crisphead, leaf, romaine, butterhead, primitive, Latin, and stem lettuces, and wild species were planted in the field in Salinas, Calif., in the Summer and Fall of 2003 with four replications. Duplicate samples from each plot were analyzed for chlorophyll (a and b), β-carotene, and lutein concentrations by high-performance liquid chromatography (HPLC). Wild accessions (L. serriola L., L. saligna L., L. virosa L., and primitive form) had higher β-carotene and lutein concentrations than cultivated lettuces, mainly due to the lower moisture content of wild lettuces. Among major types of cultivated lettuce, carotenoid concentration followed the order of: green leaf or romaine > red leaf > butterhead > crisphead. There was significant genetic variation in carotenoid concentration within each of these lettuce types. Crisphead lettuce accumulated more lutein than β-carotene, while other lettuce types had more β-carotene than lutein. Carotenoid concentration was higher in summer than in the fall, but was not affected by the position of the plant on the raised bed. Beta-carotene and lutein concentrations were highly correlated, suggesting that their levels could be enhanced simultaneously. Beta-carotene and lutein concentrations were both highly correlated with chlorophyll a, chlorophyll b, and total chlorophyll concentrations, suggesting that carotenoid content could be selected indirectly through chlorophyll or color measurement. These results suggest that genetic improvement of carotenoid levels in lettuce is feasible.