Investigations of the effects of elevated ozone (O₃) on the virus-plant system were conducted to better inform virus pathogen management strategies. One susceptible cultivar of tobacco (Nicotiana tabacum L. cv. Yongding) and resistant cultivar (Nicotiana tabacum L. cv. Vam) to Potato virus Y petiole necrosis strain (PVYN) infection were grown in open-top chambers under ambient and elevated O₃ concentrations. Aboveground biomass, foliage chlorophyll, nitrogen and total non-structural carbohydrate (TNCS), soluble protein, total amino acid (TAA) and nicotine content and peroxidase (POD) activity were measured to estimate the effects of elevated O₃ on the impact of PVYN in the two cultivars. Results showed that under ambient O₃, the resistant cultivar possessed greater biomass and lower C/N ratio after infection than the susceptible cultivar; however, under elevated O₃, the resistant cultivar lost its biomass advantage but maintained a lower C/N ratio. Variation of foliar POD activity could be explained as a resistance cost which was significantly correlated with biomass and C/N ratio of tobacco cultivar. Chlorophyll content remained steady in the resistant cultivar but decreased significantly in susceptible cultivar when stressors were applied. Foliar soluble protein and free amino acid content which were related to resistance cost changes are also discussed. This study indicated that a virus-resistant tobacco cultivar showed increased sensitivity to elevated O₃ compared to a virus-sensitive cultivar.

This paper has been published in Journal of Experimental Botany （Ye L., Fu X.& Ge F. 2011.Enhanced sensitivity to higher ozone in a pathogen-resistant tobacco cultivar. DOI: 10.1093/jxb/err361）. This project was supported by “National Basic Research Program of China” (973 Program) (No. 2012CB114103), the Innovation Program of Chinese Academy of Science (KSCX2-EW-N-005), the National Nature Science Fund of China (Nos. 31000854, 30921063) and the Open Project Program Foundation of Engineering Research Center of Biological Control，Ministry of Education (20070101).