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Andre Luiz Biscaia Ribeiro da Silva, Joara Secchi Candian, Elizanilda Ramalho do Rego, Timothy Coolong, and Bhabesh Dutta

shown in Fig. 3 . Fig. 2. Severity of cabbage black rot per cultivar during the crop development in Fall 2018 (A) and Spring 2019 (B). Values followed by same letters within each day after inoculation or week after transplanting indicate no significant

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Phillip D. Griffiths, Laura Fredrick Marek, and Larry D. Robertson

Black rot is a bacterial disease of crucifer species caused by Xanthomonas campestris pv. campestris (Xcc). Xcc is prevalent worldwide and is a destructive disease of Brassica oleracea vegetables such as cabbage, broccoli, and cauliflower

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H. Guo, M.H. Dickson, and J.E. Hunter

Resistance to black rot caused by the bacterium Xanthomonas campestris pv. campestris was studied in Brassica oleracea, B. campestris, and B. napus. Two accessions of B. napus, PI 199947 and PI 199949, exhibited the highest resistance so far found in cultivated Brassica spp. In B. napus, the high level of resistance was conferred by one dominant gene. In B. campestris, two Chinese cabbage accessions showed quantitative inheritance for moderate levels of resistance. Resistance was transferred to B. campestris from B. napus, but a unilateral incongruity was observed for black rot and morphology, but not for stem color or bolting. The bridge line 15 was used to transfer resistance to B. oleracea.

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C. Stevens, V. A. Khan, J. Y. Lu, M. A. Wilson, Z. Haung, and J. E. Brown

In 1988 and 1989 a muscadine vineyard at Tuskegeee, Alabama was treated by post plant soil solarization (PSS) (covering of moist soil around 'Carlos' muscadine plants (Vitis rotundifolia Michx.) with clear polyethylene plastic mulch to achieve high soil temperature for 30 and 75 days, respectively during PSS. Grape plants grown in solarized soils showed increases in growth response such as increased yield. Foliage of grape plants was evaluated for reaction to black rot incited by Guignardia bidwellii. A significant reduction of the foliage disease black rot was observed. The number of lesions per leaf, lesion size and percent leaves with lesions were significantly reduced by as much as 56% up to three years after solarization.

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Muhammet Tonguç and Phillip D. Griffiths

Black rot, caused by Xanthomonas campestris pv. campestris (Pam.) Dawson (Xcc), is a major bacterial disease of Brassica oleracea L. vegetables. In this study the related species Brassica carinata Braun (ethiopian mustard), which can be used to generate interspecific crosses with B. oleracea was evaluated for resistance to Xcc. Fifty-four accessions and susceptible control plants were wound inoculated with four isolates of Xcc race 4 at the juvenile stage. Of the 54 accessions tested, A 19182 and A 19183 exhibited no symptoms when inoculated with Xcc for all plants tested, and the accessions including PI 199947, PI 199949 and PI 194256 segregated for resistance to Xcc.

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Z. H. Guo, M. H. Dickson, and J. E. Hunter

Resistance to Black rot was studied in B. oleracea, B. campestris and B. napus, using three different inoculation procedures. The results indicated that hydathode inoculation without wounding and the wound suspension technique were useful for differentiating levels of resistance found in B. oleracea and B. campestris, but not in B. napus. Only the wound colony method allowed differentiation between high and moderate resistance in B napus. B. napus, PI 199947 and PI 199949, exhibited the highest resistance found in cultivated Brassica species. In B. campestris, two chinese cabbage accessions showed quantitative inheritance for moderate levels of resistance. In B. napus, the high level of reistance was conferred by one dominant gene, to which the symbol Br was assigned, whereas the moderate resistance was due to one recessive gene bm.

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Fenny Dane

A genetically engineered, bioluminescent strain of Xanthomonas campestris pv. campestris (Xcc) was used to study the effectiveness of plant growth-promoting rhizobacteria (PGPR) as disease control agents. Black-rot-susceptible cabbage plants were wound-inoculated with PGPR and wound- or mist-inoculated with bioluminescent Xcc 10 days later. Growth of the bioluminescent strain in the plants was followed over time with a low-light, charge-coupled device camera. Several PGPR strains effectively reduced growth of the bioluminescent pathogen in the plants when bacteria were introduced into the plant by wound. PGPR inoculation was less effective when bioluminescent bacteria were introduced into the plant by mist inoculation. Little effect on symptom reduction was observed.

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Laban K. Rutto, Zelalem Mersha, and Mizuho Nita

control organically. Among them, powdery mildew ( Uncinula necator ), downy mildew ( Plasmopara viticola ), black rot ( Guignardia bidwellii ), phomopsis cane and leaf spot ( Phomopsis viticola ), and botrytis bunch rot ( Botrytis cinerea ) are some of the

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Phillip D. Griffiths and Cathy Roe

Eighteen cabbage breeding lines and cultivars were evaluated for resistance to black rot caused by Xanthomonas campestris pv. campestris following wound and spray inoculations at the juvenile and mature stages. Plants were evaluated using four inoculation procedures (juvenile wound, juvenile spray, mature wound, and mature spray) in replicated greenhouse and field experiments. The breeding lines Badger #16, Cornell 101, Cornell 102, NY 4002 and accession PI 426606 exhibited high levels of resistance following all inoculation procedures. `Silver Dynasty' was the most resistant commercial cultivar based on the four tests, yet ranked 12th following the juvenile wound inoculation. The juvenile spray inoculation had a high correlation with both wound and spray inoculations in field experiments (0.89 and 0.86, respectively); however, the juvenile wound inoculation did not correlate well with mature wound and spray inoculations (0.58 and 0.51, respectively). The results indicate that the juvenile wound inoculation is not the most appropriate approach for determining field resistance in Brassica oleracea, and that resistant material could be selected against using this approach. A high correlation between juvenile spray inoculation disease severity ratings and mature plant resistance indicates that plants can be evaluated effectively at the juvenile stage for mature plant resistance to black rot.

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B.M. Pryor, R.M. Davis, and R.L. Gilbertson

The susceptibility of 46 carrot cultivars to infection by Alternaria radicina Meier, Drechsler, and Eddy, causal agent of black rot disease, was evaluated in field trials with a toothpick inoculation method. Toothpicks infested with A. radicina were inserted into the shoulders of 10- to 12-week-old carrots (Daucus carota L.) and lesion areas were measured 9 to 10 weeks later. There were significant differences in lesion size among cultivars. Relatively resistant cultivars included `Panther' and `Caro-pak', and susceptible cultivars included `Royal Chantenay' and `Nogales'. Nine of the cultivars were inoculated with A. radicina-infested toothpicks and maintained in cold-storage for 10 weeks. Lesion development was greater in cold-storage than in the field, but the relative ranking of cultivars in terms of resistance to A. radicina was similar.