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Sukhvinder Pal Singh and Zora Singh

concentrations of antioxidants in the peel and flesh tissues of fruit reduced the incidence of senescence-related disorders ( Hodges et al., 2004 ). Fruit of japanese plum are chilling-sensitive ( Crisosto et al., 2004 ; Singh et al., 2009 ). The sensitivity to

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Alexis K. Nagel, Hetal Kalariya, and Guido Schnabel

instance, despite the important economic impacts that root diseases can have on fruit production, only a few GM fruit tree species have been engineered for resistance to root-associated pathogens ( Petri and Burgos, 2005 ). Transgenic plum ( Prunus

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Gal Sapir, Raphael A. Stern, Martin Goldway, and Sharoni Shafir

Self-incompatibility (SI) is the ability of a fertile hermaphrodite flowering plant to prevent self-fertilization by discriminating between self and nonself pollen. Japanese plum ( Prunus salicina Lindl.), a species of the Rosaceae family

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Akiko Watari, Toshio Hanada, Hisayo Yamane, Tomoya Esumi, Ryutaro Tao, Hideaki Yaegaki, Masami Yamaguchi, Kenji Beppu, and Ikuo Kataoka

-compatibility (SC) in Prunus fruit tree species ( Ikeda et al., 2004b ; Tao et al., 2000 , 2002a , 2002b ). There have been several reports on the characterization of japanese plum S-RNase and SFB . Yamane et al. (1999) first isolated a japanese plum S

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J. D. Norton, G. E. Boyhan, and B. R. Abrahams

Plum production in the Southeastern United States is limited because cultivars are susceptible to bacterial canker (Pseudomonas syringae), bacterial fruit and leaf spot (Xanthomonas pruni), black knot (Apisporina morbosa) and plum leaf scald (Xylella fastidiosa). Evaluation of four new cultivars developed by the Alabama Agricultural Experiment Station indicated that AU-Rubrum, AU-Rosa and AU -Cherry were resistant to all the diseases listed, and AU-Amber was resistant to all excapt A. morbosa. Disease ratings were made on trees in six experimental plantings in Alabama, in Georgia test plantings and in grower trials.

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J.D. Norton, G.E. Boyhan, and B.R. Abrahams

Forty eight cultivars and seedlings of plum involving the species Prunus americana, P. auqustifolia, P. cerasifiera, P. munsoniana, P. salicina, P. simoni, and P. triflora were evaluated for the presence of xylem limiting bacteria (Xyllela fastidiosa) and tree longevity. Plum leaf scald (PLS) ratings, based on the percent of scalded leaves in the tree were correlated with the concentrations of bacteria in the twigs and leaf petioles. Observations of symptoms of PLS and monitoring of progeny from interspecific crosses, cultivars, and seedlings indicate that resistance to the PLS organism is present in the Auburn material and heritable. Uniform infection of seedlings was made by double budding of one year whips with buds from infected trees. Resistance to PLS has been incorporated into horticultural types and seedlings are currently being evaluated for possible release for commercial and home use.

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J.D. Norton, G.E. Boyhan, and B. Tangsukkasemsan

Plum leaf scald (PLS) caused by the organism Xylella fastidiosa is one of the most serious diseases of plum. After X. fastidiosa was identified as the causal agent for PLS, a feral source (Starcher no. 1) was used extensively in the breeding program. Microscopic (phase contrast) examinations of vacuum extracts and petiole squashes and later ELISA were used to determine PLS infection and later were correlated with a rating index for PLS and tree longevity. Cultivars, species, and their progeny, including Prunus americana, P. angustifolia, P. cerasifera, P. munsoniana, P. salicina, P. simoni, P. bullata, and P. triflora were evaluated. Observations indicate that resistance is heritable and controlled by recessive genes. ELISA and visual observation indicated that an Auburn Univ. seedling (CD 122) was free from this disease.

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B. Tangsukkasemsan, J.D. Norton, and G.E. Boyhan

Naturally infected plum leaves were collected during Aug. and Sept. 1994 to evaluated for the presence of Xylella fastidiosa, the causal agent of plum leaf scald (PLS). Leaves were from trees at least 4 years old in variety trials at four locations in Alabama. ELISA tests for X. fastidiosa were used to determine the presence of the organism in infected trees. The symptoms also were evaluated with a rating index for PLS. Some plum cultivars (i.e., `AU-Producer', `Morris', `Explorer', and `AU-Cherry') showed high tolerance to PLS. Both ELISA tests and visual observation indicated that an Auburn Univ. seedling (CD-l 22) was free from this disease. PLS infection was lower in North Alabama compared to Central Alabama.

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D.A Grantz, W.A. Retzlaff, L.E. Williams, and T.M. DeJong

Models indicate that ozone inhibits carbon assimilation largely in the upper canopy, due to light and ozone gradients. We document yield reductions and ozone gradients in Casselman plum in open-top ozone fumigation chambers. Ambient air (12 hr mean ozone = 0.050 ppm), charcoal filtered air (0.034 ppm) and ambient air plus added ozone (0.094 ppm) were circulated in the chambers. Additional trees grew outside the chambers (0.058 ppm). Outside the chambers large vertical and horizontal gradients in ozone within the canopy were documented, but these were absent in the chambers. Ozone decreased leaf photosynthesis by 31% and 58%, and fruit yield by 20% and 66%, in the ambient and ozone enriched relative to filtered chambers. Despite altered gradients, yield and photosynthesis of exposed leaves were similar inside and outside the chambers in ambient air. Compensatory changes in leaf function may be involved.

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Thomas G. Beckman, Jose X. Chaparro, and Wayne B. Sherman

prove useful as a semidwarf rootstock in which a less vigorous tree is preferred. Origin ‘Sharpe’ is a putative plum hybrid rootstock of unknown origin discovered in Florida by the late Prof. Ralph Sharpe and tested under the designation of FLA1