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Sandra L. Uratsu, Hamid Ahmadi, Royce S. Bringhurst and Abhaya M. Dandekar

Several strains of Agrobacterium tumefaciens and A. rhizogenes were shown to form tumors on runners of the diploid strawberry species Fragaria vesca L. Tumors, weighing from 0.1 to 8.3 mg, appeared from 2 to 4.5 weeks after infection. The majority of tumors tested for opine synthesis by high-voltage paper electrophoresis analysis showed positive results. These results demonstrate that diploid strawberry plants are susceptible to infection with Agrobacterium and that there are differences in the relative virulence of Agrobacterium strains.

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Fokar Mohamed and Richard Durham

Agrobacterium vitis is the causal organism of crown gall in grapevine. Infection is particularly severe in areas that experience winter damage to vines. Improving resistance to A. vitis will require a detailed knowledge about this organism. In this study, 18 grapevine isolates of A. vitis were collected from different locations near Lubbock, Texas. Isolates were subjected to a phenotypic characterization using 12 biochemical tests, including production of alkali from L-tartrate, production of 3-ketolactose, utilization of citrate, and others. Previously characterized isolates of A. vitis and A. tumefaciens obtained from the American Type Culture Collection served as positive and negative controls in these assays. Isolates were also evaluated for host range, tumor morphology, and opine utilization, and were compared at the molecular level by restriction fragment length polymorphism analysis of the oncogenic regions of the T-DNA plasmid. Although all isolates were able to metabolize tartrate and grow on Roy–Sasser media, there was much variability based on other tests. Twelve of 18 isolates were able to utilize octopine as a sole carbon source. All isolates tested thus far have been pathogenic on tomato and tests on grapevines are underway.

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G.C. Martin, A.N. Miller, L.A. Castle, J.W. Morris, R.O. Morris and A.M. Dandekar

The udiA gene encoding the enzyme β -glucuronidase (GUS) appears promising as a genetic marker for early confirmation of successful plant cell transformation. Two strains of Agrobacterium rhizogenes and eight strains of A. tumefaciens were selected as hosts to carry a binary plasmid (pBI121) containing the marker gene encoding the GUS marker that is controlled by the CaMV35S promoter. Presence of plasmid pBI121 in the bacteria was confirmed by resistance to kanamycin, plasmid re-isolation, and restriction enzyme analysis. When the GUS enzyme was expressed in transformed plant cells, reaction with the histochemical substrate 5-bromo-4-chloro-3-indolylglucuronide (X-gluc) lead to blue pigment development. Expression of GUS in viable bacteria that had not been eliminated from transformed tissue caused problems with the early transformation detection in radish, peach, and apple stem sections by also producing a positive X-gluc color reaction. Putative transformation of apple xylem parenchyma callus was accomplished, as judged by resistance to kanamycin, opine analysis, GUS marker gene expression, and presence of the APH(3')11 enzyme. In this system, elimination of bacterial contamination was accomplished during multiple culture transfers on selective media. To be more useful as a marker, the GUS gene should be coupled with a promoter that will not be expressed by Agrobacterium. Parenchyma callus may serve as a primary screen to provide an efficient way of determining the ideal strain for transformation of deciduous tree fruit genera. In our studies, strain A281 consistently proved to be a vector superior to others tested.

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Bing Liu, Hong Zhou, Sha Cao, Yi-ping Xia and Rajeev Arora

; Hincha et al., 2002 ) whereas others have opined that sugars are needed as substrates for the synthesis of cryoprotectants ( Klotke et al., 2004 ). Our data indicate that increasing concentration of leaf starch generally coincided with the loss of LFT and

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Victoria M. Anderson, Douglas D. Archbold, Robert L. Geneve, Dewayne L. Ingram and Krista L. Jacobsen

., 2011 ; Nogues et al., 1998 ; Selmar and Kleinwaechter, 2013 ). However, Selmar and Kleinwaechter (2013) opine that this is an oversimplification, and that drought stress may cause a plant to redirect carbon from growth to increased secondary