@article{romero_kousik_ritchie_2002, title={Temperature sensitivity of the hypersensitive response of bell pepper to Xanthomonas axonopodis pv. vesicatoria}, volume={92}, DOI={10.1094/PHYTO.2002.92.2.197}, abstractNote={ When bacterial spot-resistant pepper plants carrying resistance gene Bs2 and infiltrated with incompatible strains of Xanthomonas axonopodis pv. vesicatoria carrying a functional avrBs2 gene (races P1 and P3) were incubated at 32°C, they exhibited an electrolyte leakage and bacterial multiplication pattern in planta similar to that obtained with a compatible strain (race P4) carrying a nonfunctional avrBs2 gene. They also developed disease-like symptoms. Pretreatment of incompatible bacteria at 32°C before infiltration caused a delay in electrolyte leakage less pronounced than that caused by exposing plants to 32°C. Also, plants had to be exposed to 32°C for an hour prior to inoculation to increase symptom expression. These data suggest that the Bs2 gene is temperature sensitive. In other experiments, the avrBs1-Bs1 interaction appeared to be the most heat tolerant and thus the least likely to revert to compatible, whereas the avrBs3-Bs3 interaction had an intermediate sensitivity to elevated temperatures. }, number={2}, journal={Phytopathology}, author={Romero, A. M. and Kousik, C. S. and Ritchie, D. F.}, year={2002}, pages={197–203} }
 @article{romero_kousik_ritchie_2001, title={Resistance to bacterial spot in bell pepper induced by acibenzolar-S-methyl}, volume={85}, ISSN={["0191-2917"]}, DOI={10.1094/pdis.2001.85.2.189}, abstractNote={ Bell pepper plants sprayed with the chemical acibenzolar-S-methyl (ABM, Actigard 50 WG) showed resistance to subsequent infections with the bacterial spot agent Xanthomonas axonopodis pv. vesicatoria. Induction of resistance was independent of the cultivar used, and was expressed as early as 3 days after treatment and continued for at least 2 weeks. In the field, applications of ABM every 2 weeks, alone or in combination with copper, resulted in disease control similar to the standard treatment of copper plus maneb. Yield response was variable, with certain combinations of chemical treatments and cultivars producing yields as large as the copper plus maneb treatment. In contrast, weekly applications during the entire crop season had a negative impact on yield. In plots maintained free of bacterial spot, applications of ABM every 2 weeks caused a reduction in yield for one cultivar of six tested. The use of chemical inducers for the control of bacterial spot on bell pepper, while generally promising, may result in an unpredictable loss in fruit yield. }, number={2}, journal={PLANT DISEASE}, author={Romero, AM and Kousik, CS and Ritchie, DF}, year={2001}, month={Feb}, pages={189–194} }
 @article{kousik_ritchie_1999, title={Development of bacterial spot on near-isogenic lines of bell pepper carrying gene pyramids composed of defeated major resistance genes}, volume={89}, ISSN={["0031-949X"]}, DOI={10.1094/phyto.1999.89.11.1066}, abstractNote={Disease severity caused by races 1 through 6 of Xanthomonas campestris pv. vesicatoria on eight near-isogenic lines (isolines) of Early Calwonder (ECW) with three major resistance genes (Bs1, Bs2, and Bs3) in different combinations was evaluated in the greenhouse and field. Strains representing races 1, 3, 4, and 6 caused similar high levels of disease severity, followed by races 2 and 5 on susceptible ECW. Race 3 caused severe disease on all isolines lacking resistance gene Bs2. Race 4, which defeats Bs1 and Bs2, caused less disease on isoline ECW-12R (carries Bs1 + Bs2), than on isolines ECW, ECW-10R (carries Bs1), and ECW-20R (carries Bs2). Similar results were obtained with race 4 strains in field studies conducted during 1997 and 1998. In greenhouse studies, race 6, which defeats all three major genes, caused less disease on isoline ECW-13R (carries Bs1 + Bs3) and ECW-123R (carries Bs1 + Bs2 + Bs3) than on isolines ECW, ECW-10R, ECW-20R, and ECW-30R (carries Bs3), but not on ECW-23R (carries Bs2 + Bs3). In greenhouse studies with commercial hybrids, strains of races 4 and 6 caused less disease on Boynton Bell (carries Bs1 + Bs2) than on Camelot (carries no known resistance genes), King Arthur (carries Bs1), and X3R Camelot (carries Bs2). Race 6 caused less disease on hybrid R6015 (carries Bs1 + Bs2 + Bs3) and Sentinel (carries Bs1 + Bs3) than on Camelot. Residual effects were not as evident in field studies with race 6 strains. Defeated major resistance genes deployed in specific gene combinations (i.e., gene pyramids) were associated with less area under the disease progress curve than when genes were deployed individually in isolines of ECW or commercial hybrids. Successful management of bacterial spot of pepper is achieved incrementally by integrating multiple tactics. Although there is evidence of residual effects from defeated genes, these effects alone likely will not provide acceptable bacterial spot control in commercial production fields. However, when combined with sanitation practices and a judicious spray program, pyramids of defeated resistance genes may aid in reducing the risk of major losses due to bacterial spot.}, number={11}, journal={PHYTOPATHOLOGY}, author={Kousik, CS and Ritchie, DE}, year={1999}, month={Nov}, pages={1066–1072} }
 @article{kousik_ritchie_1998, title={Response of bell pepper cultivars to bacterial spot pathogen races that individually overcome major resistance genes}, volume={82}, ISSN={["0191-2917"]}, DOI={10.1094/pdis.1998.82.2.181}, abstractNote={The effect of major resistance genes (Bs1, Bs2, and Bs3) or gene combinations for resistance to bacterial spot of bell peppers (Xanthomonas campestris pv. vesicatoria) in 15 commercial cultivars on disease reduction and yield were studied during 1995 and 1996. Reaction of cultivars to specific races (races 1, 2, or 3) of the pathogen corresponded with seed company claims for resistance against these races. Races 1 to 4 were used as initial inoculum in 1995, and races 1 to 6 in 1996 field experiments. Cultivars with no known resistance genes to bacterial spot (e.g., Camelot, Jupiter, and Valiant), a single resistance gene (X3R Camelot, King Arthur), or a combination of Bs1 and Bs3 genes (Guardian, Sentinel, and Admiral) were severely diseased. Yields were reduced in all inoculated cultivars compared to non-inoculated cultivars used as controls. Although races 4 and 6 caused significant disease in cultivars with only Bs1 (King Arthur) or Bs2 (X3R Camelot) genes, cultivars with a combination of Bs1 and Bs2 (Boynton Bell, PR9300-8) had much lower levels of bacterial spot. Roger 4178, a hybrid with a combination of Bs1, Bs2, and Bs3 genes, had the lowest disease ratings. Overall, race 3 was predominant during 1995, while races 3 and 6 were recovered most frequently in 1996.}, number={2}, journal={PLANT DISEASE}, author={Kousik, CS and Ritchie, DF}, year={1998}, month={Feb}, pages={181–186} }
 @article{kousik_ritchie_1996, title={Disease potential of pepper bacterial spot pathogen races that overcome the Bs2 gene for resistance}, volume={86}, number={12}, journal={Phytopathology}, author={Kousik, C. S. and Ritchie, D. F.}, year={1996}, pages={1336} }
 @article{kousik_sanders_ritchie_1996, title={Mixed genotypes combined with copper sprays to manage bacterial spot of bell peppers}, volume={86}, ISSN={["0031-949X"]}, DOI={10.1094/Phyto-86-502}, abstractNote={Effects of genotype mixtures combined with three copper + maneb spray schedules on bacterial spot (Xanthomonas campestris pv. vesicatoria) of bell peppers were tested from 1993 to 1995. Planting patterns used for mixing the resistant and susceptible genotypes were either rows of resistant plants interplanted in rows of susceptible plants or a checkerboard pattern. In 1993, three races (1, 2, and 3) of the pathogen were used as inoculum, and two races (1 and 2) were used in 1994 and 1995. Interplanting of resistant and susceptible peppers and application of copper sprays resulted in less disease and greater yields. In 1994, the genotype mixtures had 6 to 45% less disease than pure stands of the susceptible genotype with three spray schedules. In 1995, the mixtures had 15 to 44% less disease compared with pure stands of the susceptible genotype without the copper + maneb sprays. Significantly less disease was observed for the susceptible genotype in the checkerboard pattern compared with pure stands of the susceptible genotype during 1994 and 1995. For several of the mixtures, no significant differences in yield between the weekly (7-day) and the biweekly (14-day) spray schedules were observed. There was a tendency for one race of the pathogen to predominate, depending on the host resistance gene(s) present. The checkerboard pattern of mixing genotypes was more effective in reducing disease in the susceptible genotype compared with row patterns. The use of genotype mixtures could be viewed as added insurance against the bacterial spot pathogen, in addition to copper spray programs to prolong the durability of genotypes.}, number={5}, journal={PHYTOPATHOLOGY}, author={Kousik, CS and Sanders, DC and Ritchie, DF}, year={1996}, month={May}, pages={502–508} }
 @article{kousik_ritchie_1996, title={Race shift in Xanthomonas campestris pv vesicatoria within a season in field-grown pepper}, volume={86}, ISSN={["1943-7684"]}, DOI={10.1094/Phyto-86-952}, abstractNote={Race shifts in Xanthomonas campestris pv. vesicatoria, (proposed: X. axonopodis pv. vesicatoria), the pepper bacterial spot pathogen, were studied in the field during 1993 and 1994. In 1993, Early Calwonder (ECW) pepper plants inoculated with rifampicin-resistant race 1 strain Xcv 33 rif , which carries avirulence gene avrBs3, were planted in a plot of ECW-30R plants, which carry the Bs3 gene for resistance to race 1 of the pathogen. Disease was observed on plants adjacent to the inoculum plants 2 weeks after inoculation, and within 10 weeks, all plants were diseased. Rifampicin-resistant single colonies isolated from diseased ECW-30R plants were screened for race reaction on pepper differentials, and all were race 3 because they were compatible on ECW-30R. Total DNA from 25% of the single colonies hybridized to an avrBs3 gene probe, and the plasmid carrying avrBs3 was not detected in the colonies that did not hybridize to avrBs3. Similarly, in 1994 the population derived from a strain of race 2 that carries avrBs1 rapidly shifted to race 3 when inoculated plants were placed in a plot of ECW-10R plants carrying the single resistance gene Bs1. Total DNA from all isolated single colonies with the race 3 phenotype hybridized with avrBs1 and insertion element IS476. Thus, a race 3 pathogen population of X. campestris pv. vesicatoria rapidly developed from race 1 and 2 populations within a growing season in the field when exposed to a resistant pepper cultivar carrying a single resistance gene. The race shift from race 1 to 3 was due to loss of the plasmid carrying the avirulence gene or to inactivation of avrBs3. Shift from race 2 to 3 apparently resulted from insertion element IS476 inactivating avirulence gene avrBs1.}, number={9}, journal={PHYTOPATHOLOGY}, author={Kousik, CS and Ritchie, DF}, year={1996}, month={Sep}, pages={952–958} }
 @article{kousik_ritchie_1995, title={ISOLATION OF PEPPER RACE-4 AND RACE-5 OF XANTHOMONAS-CAMPESTRIS PV VESICATORIA FROM DISEASED PEPPERS IN SOUTHEASTERN US FIELDS}, volume={79}, ISSN={["0191-2917"]}, DOI={10.1094/PD-79-0540C}, number={5}, journal={PLANT DISEASE}, author={KOUSIK, CS and RITCHIE, DF}, year={1995}, month={May}, pages={540–540} }
 @article{kousik_sanders_ritchie_1994, title={Yield of bell peppers as impacted by the combination of bacterial spot and a single hail storm: Will copper sprays help?}, volume={4}, number={4}, journal={HortTechnology}, author={Kousik, C. S. and Sanders, D. C. and Ritchie, D. F.}, year={1994}, pages={356} }