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Marcos R. Sachet, Idemir Citadin, Silvia Scariotto, Idalmir dos Santos, Pedro H. Zydek and Maria do Carmo B. Raseira

, was considered adequate to estimate bacterial disease severity in peach, and can be used in epidemiological studies. Fig. 2. Diagrammatic representation of the bacterial leaf spot (BLS) severity scale developed Citadin et al. (2008) . Values are

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Huangjun Lu and Richard Raid

Bacterial leaf spot of lettuce ( Lactuca sativa L.), caused by Xanthomonas campestris pv. vitians , is an economically important disease of lettuce in the world ( Barak et al., 2001 ; Patterson et al., 1986 ; Pennisi and Pane, 1990 ; Sahin

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Ryan J. Hayes, Mark A. Trent, Beiquan Mou, Ivan Simko, Samantha J. Gebben and Carolee T. Bull

many lettuce pests, including leafminers ( Liriomyza langei ), downy mildew ( Bremia lactucae ), and bacterial leaf spot (BLS). Bacterial leaf spot of lettuce, caused by Xanthomonas campestris pv. vitians ( Xcv ), is an increasingly damaging disease

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Annelle W.B. Holder, Winston Elibox, Christopher Avey and Pathmanathan Umaharan

Bacterial leaf spot disease of anthurium ( Anthurium andraeanum L.) caused by A . anthurii ( Gardan et al., 2000 ) was first reported in the French West Indies ( Prior and Rott, 1989 ; Prior and Sunder, 1987 ; Prior et al., 1985 ) and later in

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David J. Norman and Jianjun Chen

. Recently, several studies have suggested that TiO 2 application suppresses bacterial and fungal pathogens of field crops. In cereal crops, severity and incidence of Curvularia leaf spot ( Curvularia lunata ) and bacterial leaf blight ( Xanthomonas oryzae

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Mathews L. Paret, Aaron J. Palmateer and Gary W. Knox

). Among the many diseases reported on roses, bacterial leaf spot caused by Xanthomonas sp. is a relatively new disease affecting nursery production. The disease is widespread and documented in Florida on the shrub rose varieties ‘RADrazz’ (Knock Out

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Ryan J. Hayes, Carolee T. Bull, Polly H. Goldman and Edward J. Ryder

Bacterial leaf spot of lettuce caused by Xanthomonas campestris pv. vitians (Xcv) is an important lettuce disease in California. No adequate control measures have been found, although resistance exists in several heirloom cultivars. Deployment of cultivars resistant to bacterial leaf spot will reduce these periodic and costly disease events. The objectives of this research were to 1) identify new sources of resistance within modern crisphead cultivars and 2) select for resistance in `Salad Crisp' × `Iceberg' progeny. Field plots were established and grown with overhead irrigation, and a three-strain mixture of Xcv was applied until runoff 1 week after thinning at 1 × 109 CFU/mL. Twenty-six crisphead cultivars were tested in unreplicated field trials and rated on a 1 (susceptible) to 4 (resistant) scale. Selection was carried out between and within families from the F2 to F4 generation. Sixteen F3 families were evaluated in unreplicated plots, and 12 F5 families were tested in replicated plots for disease incidence and severity. No usable levels of resistance were identified in the modern crisphead cultivars tested to date. All F3 families had resistance greater than `Iceberg', and 19 plants from eight families were selected for further breeding. Subsequently, 12 plants from two F4 families were selected. Replicated trials of 12 F5 families indicated that all lines have disease severity comparable to both parents. Breeding lines from crosses to `Salinas 88' are currently being developed.

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Annelle W.B. Holder, Winston Elibox and Pathmanathan Umaharan

( Prior et al., 1985 ). Necrotic spots are surrounded by greasy margins and narrow, bright chlorotic halos ( Dilbar and Gosine, 2003 ; Prior et al., 1985 ). Under conditions of high humidity, bacterial slime oozes from the leaf margins. On spathe tissues

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Brent Rowell, Terry Jones and William Nesmith

Kentucky growers currently produce about 1300 acres of bell peppers worth $2 million for both fresh market and processing. Bacterial leaf spot (BLS) caused by Xanthomonas campestris pv. vesicatoria has been the scourge which continues to limit expansion of pepper production in the state. Fourteen new BLS-resistant varieties and experimental lines were evaluated together with two standard (susceptible) varieties in 1995 at two locations. All entries were exposed to an induced BLS epidemic at one location but were kept disease-free at the second location. Field resistance to four races of BLS was high for all but one of the lines tested, which claimed resistance to races 1, 2, and 3. Cultivars with resistance to only race 2 or races 1 and 2 of the pathogen were no different from susceptible checks in terms of yields and disease resistance. Six entries performed well at both locations; these will be included in further trials in 1996.

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B.L. Topp, W.B. Sherman, R.E. Stall, G.V. Minsavage and C.J. Wilcox

Four greenhouse leaf inoculation methods for screening Japanese plum (Prunus salicina L. and hybrids) for resistance to Xanthomonas campestris pv. pruni (Smith) Dye were compared for repeatability, ability to differentiate among plant genotype responses, and correlations with field ratings. Clonally propagated trees were inoculated artificially in a greenhouse by immersing leaves in 2.5 × 108 cfu/ml inoculum (DIP), rubbing the adaxial side of leaves with a slurry of 2.5 × 108 cfu/ml inoculum and Carborundum powder (CARB), infiltrating leaves with 5 × 105 cfu/ml inoculum using a needle-less syringe (INFS), and infiltrating with 5 × 106 cfu/ml inoculum (INF6). No greenhouse method was superior in all assessment categories. The CARB method was most repeatable (t = 0.78) but had a low Spearman's correlation (rs = 0.29), indicating that greenhouse rankings did not correspond closely with field rankings. The INF6 method was unsuitable because it did not differentiate between plant genotypes. The DIP method appeared most suitable, having moderate repeatability (t = 0.46) for four observations per leaf and moderate Spearman's correlation with field performance (rs = 0.56). The INF5 method may be appropriate for identifying bacterial spot resistance that is associated with resistance in the leaf mesophyll.