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Tripti Vashisth and Anish Malladi

al., 2012 , 2013 ; Vashisth and Malladi, 2013 ). Developmentally regulated mature fruit detachment through the physiological process of abscission occurs within the AZ located at the PPJ ( Vashisth and Malladi, 2013 ). Application of MeJa (20 m m

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J.K. Burns, U. Hartmond, R. Yuan, and W.J. Kender

Methyl jasmonate (Me-Ja) is a naturally occurring ubiquitous compound in plants. Me-Ja is considered to be a putative plant hormone because of its effect on plant processes such as senescence, germination, tuber formation, signal transduction, ethylene production, and abscission at low exogenous concentrations. We applied Me-Ja to fruit or whole trees of `Hamlin' or `Valencia' orange to determine the potential of this compound as a mature fruit abscission agent. Me-Ja (0, 1, 5, 10, or 20 mM in 0.1% Kinetic adjuvant) was applied to whole trees with a handgun or boom sprayer rates of 4850 and 1790 L·ha–1, respectively. Alternatively, tree fruit were dipped in Me-Ja solutions. Fruit drop, leaf drop and ethylene production in both fruit and leaves and fruit detachment force in fruit were monitored at various times up to 2 weeks after application. Me-Ja treatment resulted in increased ethylene production in fruit and leaves 1 to 2 days after application. Fruit detachment force significantly declined 6 to 10 days after application followed by significant fruit drop. Applications of Me-Ja >10 mM resulted in an unacceptable amount of canopy defoliation. The results suggest that Me-Ja has potential as an abscission agent for citrus. Future work will focus on improving uniformity of application and response.

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Anish Malladi, Tripti Vashisth, and Scott NeSmith

cultivar, Briteblue. In the control, mechanical shaking of ≈14.4 s was required to detach all the fruit for a sample branch ( Fig. 4 ). The application of MeJa (20 m m ) reduced the time taken for fruit detachment by almost 5-fold (3 s). Similar to the MeJa

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Charles L. Rohwer and John E. Erwin

Jasmonates are a class of plant hormones involved in plant defense and stress responses. For example, jasmonate-induced defense responses in Lycopersicon esculentum include increases in activity of proteinase inhibitors, polyphenol oxidases, and peroxidases. As part of our efforts to reduce or control greenhouse pest infestations, we hypothesized that methyl jasmonate (MeJA) could induce these biochemical changes in common greenhouse crops. We studied Impatiens wallerana `Super Elfin Pink', L. esculentum `Big Boy', Petunia ×hybrida `Bravo Lavendar', Viola ×wittrockiana `Imperial Beaconsfield', Coleus ×hybridus `Wizard Jade', Nicotiana alata `Saratoga Lime', Pelargonium ×hortorum `Pinto Pink', and Tagetes erecta `Antigua Primrose'. Polyphenol oxidase and peroxidase activity was studied in the first four species, and proteinase inhibitors were studied in all eight. We sprayed plants with 0, 5 × 10-6, or 10-4 molar MeJA and made measurements after 24 hours. We detected a small increase in polyphenol oxidase activity of plants treated with 10-4 molar MeJA; 5 × 10-6 molar had no effect, and L. esculentum had the highest polyphenol oxidase activity. Peroxidase activity was not affected by MeJA. I. wallerana had the highest peroxidase activity, L. esculentum and V. ×wittrockiana had the lowest. 5 × 10-6 molar MeJA increased proteinase inhibitor activity in most species, and 10-4 molar increased activity in every species except P. ×hortorum.

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Elisabet Claveria and Ramon Dolcet-Sanjuan

Micropropagation of Pistacia vera L. `Mateur' was improved with the addition of methyl jasmonate (MeJA) to the multiplication and rooting media. Shoot tip cultures established from grafted trees were maintained on a modified Murashige and Skoog medium containing 5μM BA and 0.05μM IBA. Addition of 1μM MeJA improved the multiplication rate but inhibited shoot growth when present at higher concentrations. Rooting experiments comparing the effects of IAA, NAA, or IBA at 0, 1, 3.2, 10, or 31.6 μM demonstrated a significant effect of temperature on auxin root induction for shoots maintained at 25 or 28°C. At 25°C NAA was better than IAA or IBA, whereas no differences among auxins were observed at 28°C. Addition of MeJA (0, 0.3, 1, 3.2, or 10 μM) to the best rooting media significantly improved the rooting percentage and root number. Greater than 80% rooting was obtained when 1 μM MeJA was added to both the root induction medium, containing 31.6 μM NAA, and the auxin-free medium. In addition, transfer to soil and acclimation was easier for plantlets rooted in MeJA-containing medium.

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Raymond Fung*, Chien Wang, David Smith, Kenneth Gross, Yang Tao, and Meisheng Tian

Methyl salicylate (MeSA) and Methyl jasmonate (MeJA) treatments increased chilling resistance of light red tomato (Lycopersicon esculentum cv. Beefsteak) and extended shelf life and fresh-cut quality. We previously showed induction of AOX expression by low temperature and that induction of AOX transcript by MeSA and MeJA is correlated with resistance against chilling injury in peppers. Here, we investigate tomato, which is genetically closely related to peppers and belongs to the same Solanaceae family. In particular, we used four EST tomato clones of AOX from the public database that belong to two distinctly related families, 1 and 2 defined in plants. Three clones designated as LeAOX1a, 1b and 1c and the fourth clone as LeAOX2. Probes for these four genes were designed and Southern blotting done to confirm that they do not cross-hybridize. We will present data from Southern, Northern hybridization and RT-PCR to show: (1) gene copy number of each of these AOX members in the tomato genome; (2) gene-specific expression profiles in response to MeSA and MeJA in cold stored tomato; and (3) the relative transcript abundance of these four AOX genes.

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Luis Pozo, Rongcai Yuan, Igor Kostenyuk, Fernando Alférez, Guang Yan Zhong, and Jacqueline K. Burns

1-MCP is a gaseous ethylene binding inhibitor that controls or delays ethylene-related postharvest problems in a range of horticultural commodities. Our previous work demonstrated that exposure of calamondin to 1-MCP 16 hours before canopy sprays of ethephon greatly reduced unwanted leaf drop while only partially inhibiting the ability of ethephon to cause fruit loosening. The objective of this work was to determine whether formulated 1-MCP (SmartFresh) could be used in the field to stop defoliation caused by abscission agent applications without significantly altering abscission agent-induced fruit loosening. Spray solutions containing 400 mg·L-1 ethephon with 0, 1, 2.5, and 5 mm 1-MCP were applied to canopies of `Hamlin' and `Valencia' (Citrus sinensis). Timing of 1-MCP applications was a) 24 hours before, b) in combination with, or c) 24 hours after ethephon. Ethephon at 400 mg·L-1 significantly reduced fruit detachment force (FDF) but caused >70% leaf drop within 15 days after application in both cultivars. Applications of 1-MCP reduced ethephon-associated leaf abscission but had little effect on the ability of ethephon to reduce FDF. Timing of 1-MCP applications did not affect the ability of ethephon to cause fruit loosening; however, the best consistent treatment for control of leaf drop was achieved with the combined application of 5 mm 1-MCP and 400 mg·L-1 ethephon. 1-MCP was used in combination with the abscission agents coronatine, methyl jasmonate (MeJa) and 5-chloro-3-methyl-4-nitro-1H-pyrazole (CMNP) to determine its effect on leaf drop and fruit loosening. Leaf drop in trees treated with ethephon, coronatine, and MeJa was reduced by addition of 1-MCP. However, fruit loosening was largely prevented when 1-MCP was used in combination with coronatine or MeJa. Like ethephon, CMNP-induced fruit loosening was not affected by 1-MCP. The results demonstrate the ability to control ethephon-induced leaf abscission without affecting mature fruit loosening by targeting ethylene binding in citrus.

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Ahmet Korkmaz

The effects of incorporating plant growth regulators into the priming solution on low temperature germination and emergence percentage performance of sweet pepper (Capsicum annuum `Demre') seeds before and after seed storage were investigated. Seeds were primed in 3% KNO3 solution for 6 days at 25 °C in darkness containing one of the following: 1, 3, 5, or 10 μm methyl jasmonate (MeJA) or 0.05, 0.1, 0.5, or 1 mm acetyl salicylic acid (ASA). Following priming, seeds were either immediately subjected to germination and emergence tests at 15 °C or stored at 4 °C for 1 month after which they were subjected to germination test at 15 °C. Priming pepper seeds in the presence or absence of plant growth regulators in general improved final germination percentage (FGP), germination rate (G50) and germination synchrony (G10-90) at 15 °C compared to nonprimed seeds which had an FGP of 44%, G50 of 7.3 days and G10-90 of 7.3 days. Priming seeds in KNO3 solution containing 0.1 mm of ASA resulted in the highest germination percentage (91%), fastest germination rate (G50 = 2.2 days) and the most synchronous germination (G10-90 = 6.1 days). Emergence percentages were the highest for the seeds primed in the presence of 0.1 mm ASA (85%) and 3 μm MeJA (84%) while nonprimed seeds had an emergence percentage of 40%. Fastest emergence rates (E50) were also obtained from seeds primed in KNO3 supplemented with 3 μm MeJA (E50 = 15.2 days) and 0.1 mm ASA (E50 = 15.2 days). Shoot fresh and dry weights of pepper seedlings were significantly affected by priming treatments and priming in the presence of 0.1 mm ASA resulted in highest seedling shoot fresh and dry weights. Although all priming treatments improved germination performance of pepper seeds at 15 °C following 1 month of storage, inclusion of 0.1 mm ASA into the priming solution resulted in the highest germination percentage (84%) and germination rate (G50 = 3.8 days). These results indicate that priming seeds in 0.1 mm of ASA or 3 μm MeJA incorporated into the KNO3 solution can be used as an effective method to improve low temperature performance of sweet pepper seeds and that these seeds can be stored for 1 month at 4 °C and still exhibit improved germination performance at 15 °C.

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and flavonoid concentrations and antioxidant activity of untreated and MeJA-treated kale leaf samples over two seasons. z

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Scott Schaefer, Ksenija Gasic, and Schuyler Korban

Peach shoots were grown in vitro for 0, 6, 12, 24, and 48 h on a basal medium containing one of several phytohormones or chemical elicitors, including abscisic acid (ABA), indolebutyric acid (IBA), indoleacetic acid (IAA), kinetin, gibberellic acid (GA3), aminocyclopropane-1-carboxylic acid (ACC), methyl jasmonate (MeJ), and salicylic acid (SA). Northern blot analysis was conducted using the 3' end of a peach-1,3-glucanase gene, PpGns1, used as a probe. Variations in levels of PpGns1 expression patterns were observed for each of the treatments. Shoots treated with ABA displayed high levels of transcripts at 12 and 24 h, followed by a sharp decline at 48 h. Shoots treated with ACC displayed a steady increase in transcripts throughout the 48 h period. The synthetic auxin IBA displayed a steady increase in mRNA accumulation for the first 24 h followed by a sharp decline at 48 h. Shoots treated with kinetin displayed low levels of transcripts after 24 h, while GA3 did not induce any accumulation of PpGns1 transcripts. Both SA and MeJA induced steady mRNA accumulation in peach shoots over the entire 48-h period. Induction of PpGns1 in response to SA, MeJ, and ACC also resulted in observed necrotic lesions on peach shoots, thus suggesting a different defense mechanism response.