Abstract
Elevated atmospheric CO2 typically enhances photosynthesis of C3 plants and alters primary and secondary metabolites in plant tissue. By modifying the defensive signaling pathways in host plants, elevated CO2 could potentially affect the interactions between plants, viruses, and insects that vector viruses. R gene-mediated resistance in plants represents an efficient and highly specific defense against pathogens and herbivorous insects. The current study determined the effect of elevated CO2 on tomato plants with and without the nematode resistance gene Mi-1.2, which also confers resistance to some sap-sucking insects including whitefly, Bemisia tabaci. Furthermore, the subsequent effects of elevated CO2 on the performance of the vector whiteflies and the severity of Tomato yellow leaf curl virus (TYLCV) were also determined. The results showed that elevated CO2 increased the biomass, plant height, and photosynthetic rate of both the Moneymaker and the Mi-1.2 genotype. Elevated CO2 decreased TYLCV disease incidence and severity for Moneymaker plants but had the opposite effect on Mi-1.2 plants whether the plants were agroinoculated or inoculated via B. tabaci feeding. Elevated CO2 increased the salicylic acid (SA)-dependent signaling pathway on Moneymaker plants but decreased the SA-signaling pathway on Mi-1.2 plants when infected by TYLCV. Elevated CO2 did not significantly affect B. tabaci fitness or the ability of viruliferous B. tabaci to transmit virus regardless of plant genotype. The results indicate that elevated CO2 increases the resistance of Moneymaker plants but decreases the resistance of Mi-1.2 plants against TYLCV, whether the plants are agroinoculated or inoculated by the vector. Our results suggest that plant genotypes containing the R gene Mi-1.2 will be more vulnerable to TYLCV and perhaps to other plant viruses under elevated CO2 conditions.
Highlights
The atmospheric CO2 concentration, which has risen from 280 to 400 ppm since the industrial revolution, exceeds any level in the past 65,000 years and is predicted to reach 540–900 ppm by the end of this century (IPCC, 2013)
We determined the effects of elevated CO2 on Mi-1.2 gene-mediated resistance against Tomato yellow leaf curl virus (TYLCV) and its vector, B. tabaci
Inconsistent with our hypotheses that elevated CO2 would increase the resistance of plants to TYLCV in both genotype, we discovered that the effects of elevated CO2 on TYLCV infection differed between Moneymaker and Mi-1.2 plants
Summary
The atmospheric CO2 concentration, which has risen from 280 to 400 ppm since the industrial revolution, exceeds any level in the past 65,000 years and is predicted to reach 540–900 ppm by the end of this century (IPCC, 2013). Elevated CO2 increased plant resistance against Potato virus Y in tobacco and Tomato yellow leaf curl virus (TYLCV) in tomato (Matros et al, 2006; Huang et al, 2012) In the field, these plant viruses are transmitted by insect vectors, most of which are sap-sucking insects (i.e., aphids and whiteflies) whose performance could be affected by elevated CO2 (Sun et al, 2013; Wang et al, 2014). Elevated CO2 reduced whitefly abundance at 1000 ppm but had no effect at 700 ppm (Butler et al, 1986; Tripp et al, 1992; Wang et al, 2014) It is unclear whether the effects of elevated CO2 on the performance of insect vectors could in turn alter virus transmission to plants
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