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Danielle Poor

Sulfur application is a common practice in viticulture fungus control. This application has been suspected to increase grape susceptibility to spider mites. We hypothesize that sulfur may initiate a pathway that increases spider mite infection. RNA was isolated from grape leaves with various sulfur applications. Evaluation of genes being expressed will allow us to determine if sulfur application is regulating grape leaf defense mechanisms.

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M.E. Musgrave and W.J. Blackmon

The objective of this study was to investigate the respiratory pathways in the underground storage tissues (tubers, fleshy roots, and rhizomes) of Apios americana Medikus (apios). Freshly sliced tubers of experimental breeding lines expressed variable capacities for alternative respiration, depending on genetic background, although the alternative respiratory pathway was not engaged in any of the apios tissues tested. The capacity of the alternative pathway present upon slicing was consistent with genetic line over the 5 years of the study. Respiration patterns of tubers and fleshy roots were comparable within a genetic line; however, substantial differences were found in the respiration of the nonthickened sections of rhizomes compared with the storage tubers. Total respiration of stored rhizomes was high (up to 2.7 μl O2/g per rein) compared to that of tubers (up to 0.9 μl O2/g per min). Rhizome tissue respiration had a large capacity for alternative respiration (40%-60% of total respiration), while tuber tissue had 0% to 73% alternative respiration, depending on genetic source. Epidermal layers, obtained from tubers that lacked a capacity for alternative respiration after slicing, had alternative respiration rates comparable to those of rhizomes. Furthermore, the alternative pathway could be induced in these tubers through conventional aging techniques. Etiolated shoots and rhizomes growing from these tubers also had an alternative respiration capacity that was half of the total rate. These results demonstrate that, although the capacity for alternative respiration is present in tissues of apios, freshly sliced tubers may or may not exhibit this pathway depending on genetic background. This attribute maybe significant as apios undergoes further domestication.

Open access

Lisa Tang and Carol J. Lovatt

, 1969 ; Nakajima et al., 1992 ; Southwick and Davenport, 1986 ; Tang and Lovatt, 2019 )]. The water-deficit floral-induction pathway in citrus is of particular interest because drought is increasingly pervasive due to climate change ( Easterling et al

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William G. Hembree, Thomas G. Ranney, Brian E. Jackson, and Mark Weathington

potential for pollen contamination, mislabeling, and variable reproductive pathways (e.g., unreduced gametes, apomixis, etc.). These challenges underscore the need for clone-specific data regarding cytogenetics for individual accessions and breeding lines

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James T. Brosnan, Dean A. Kopsell, Matthew T. Elmore, Gregory K. Breeden, and Gregory R. Armel

-geranyl pyrophosphate to produce phytoene, the first C 40 carotenoid ( Buchanan et al., 2000 ). Phytoene is metabolized to lycopene through a series of desaturation reactions ( Buchanan et al., 2000 ). Branching of the pathway occurs when lycopene is cyclized into α

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Haejeen Bang, Sunggil Kim, Daniel I. Leskovar, and Stephen King

Fruit color and carotenoid composition are important traits in watermelon. Watermelon fruit color inheritance has revealed that several genes are involved in color determination. Carotenoids are known to have various functions in plants and animals, such as providing antioxidant activity and other health benefits for humans, and UV protection and pigmentation for plants. Differential gene activity in the carotenoid biosynthetic pathway may result in different color determination of mature fruit. Eight genes encoding enzymes involved in the pathway were isolated and their structures were characterized. While obtaining full-length cDNA of these enzymes, two single-nucleotide polymorphisms were detected in a coding region of lycopene β-cyclase (LCYB). These SNP markers showed cosegregation with red and canary yellow fruit color based on the genotyping of two segregating populations. This will lead to development of a codominant molecular marker for the selection of LCYB allele, which may allow breeders to distinguish between red and canary yellow watermelon fruit colors at the seedling stage.

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Neal Courtney-Gutterson

The biosynthetic pathway for anthocyanins has been studied using genetic, biochemical and molecular biological tools. In the past decade, the core pathway genes have been cloned; a number of genes which act to modify anthocyanin structure have been cloned more recently. The first results in color modification have been reduced flower color intensity using gene suppression methods. In particular, we have utilized chalcone synthase (CHS) and dihydroflavonol reductase (DFR) genes and sense suppression in our experimental system, Petunia hybrida, and in the commercial crops, chrysan-themum (Dendranthema morifolium) and rose (Rosa hybrida). In petunia a range of new phenotypes was obtained; genetic stability of suppressed pheno-types will be described. In chrysanthemum a white-flowering derivative of a pink-flowering variety will be described. In rose uniform, partial reduction in pigment intensity throughout the flower was observed in over a dozen trans-genie derivatives of a red-flowering variety.

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Rufino Perez and Randolph M. Beaudry

Volatile production is known to change with stages of plant organ development. Research has primarily focused on ripening-related volatiles; however, the potential exists to use volatiles as markers of organ damage and senescence. We have employed gas chromatography/mass spectrometry to establish stages of senescence based on volatile profiles of whole and lightly processed broccoli and carrot. An air-tight chopping apparatus was used as a flow-through chamber system and the exit gas stream analyzed for each commodity with and without tissue disruption. For carrot, isoprenoid pathway volatiles, such as 3-carene, caryophellene, α-caryophellene, and β-pinene, increase with damage and tissue senescence. Similar trends were obtained for broccoli with volatiles characteristic of β-oxidation and shikimic acid pathways. Time and condition-related volatile profile changes will be presented for carrot, broccoli, and strawberry.

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Brian J. Just* and Philipp W. Simon

While the carotenoid biosynthetic pathway has been studied several horticultural and agronomic crops, very little information exists for this conserved pathway in carrot, a primary source of dietary carotenoids. Though orange carrots are the most familiar color to Western consumers, yellow, red, and white carrots also exist and have been historically important. Modern carrot breeders are showing renewed interest in these unusual color phenotypes. Beta- and alpha-carotene are the primary pigments in orange carrot roots. Yellow carrots accumulate xanthophylls (oxygenated carotenes), red carrots accumulate lycopene (the precursor to alpha- and beta-carotene), and white carrots accumulate no detectable pigments. Differences between these phenotypes are usually monogenic or oligogenic. Our research has focused on identifying putative genes for carotenoid biosynthetic enzymes in the carrot genome, mapping them, and examining expression patterns in various tissues and carrot root pigment phenotypes. We are using this information to create a carrot pigment biosynthesis function map incorporating biosynthetic enzymes, major carrot color genes, and gene expression information.

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John K. Fellman

Volatile ester molecules are important contributors to the perception of fruit taste. Biosynthesis of volatile compounds occurs via several biochemical pathways. Ongoing studies have concentrated on alcohol acetyl transferase, the terminal step in the acetate ester synthesis pathway. Our studies on volatile biosynthesis in apples have revealed several interesting phenomena. First, the nature and amount of volatile compounds are cultivarand strain-dependent. Studies with `Delicious' show a relationship between amount of peel coloration and flavor volatile content of tissue. Second, it is possible to manipulate the preharvest growing environment to influence the content of some volatiles in the fruit. Third, generation of volatiles is closely linked to the onset of climacteric ripening. Other experiments show the response of apples to different storage conditions with regard to volatile ester synthesis. In some cultivars softening apparently provides ester precursor molecules, leading us to speculate that there are glycosidically bound intermediates that are liberated by the action of cell-wall degradation.