Insititute of soil science
Supported by the National Natural Science Foundation of China (No. 31870423), the Key-Area Research and Development Program of Guangdong Province, China (No. 2020B0202010006), and the Carbon Peaking and Carbon Neutrality Special Fund for Science and Technology from Nanjing Science and Technology Bureau (No. 20221103)
【Objective】Sheath blight (ShB) is a soil-borne disease, whose occurrence and development seriously threatens rice (Oryza sativa L.) production. However, it is still unclear how elevated CO2 concentration ([CO2]) and temperature affect pathogenesis-related proteins (PR proteins) and defense enzymes in plants infected with Rhizoctonia solani.【Method】In this study, temperature by free-air CO2 enrichment (T-FACE) system was used with four treatments: ambient condition; elevated [CO2] ([CO2] up to 590 μmol·mol-1); elevated temperature (temperature increased 2 ℃); the combination of elevated [CO2] and elevated temperature. Two cultivars (a susceptible variety, Lemont and a resistant variety, YSBR1) were planted to explore the response of PR proteins and defense enzymes activities in leaves and stems for two cultivars by artificial inoculation of R. solani, as well as basic physical and chemical properties of soil.【Result】Results indicated that there was no significant difference in the growth rate of R. solani on soil extract medium, which was made by bulk soil under elevated [CO2] and temperature. After inoculation with R. solani, the development rate of the ShB lesion was not related to the basic physical and chemical properties of soil. The combination of elevated [CO2] and elevated temperature induced different effects on PR proteins and defense enzymes activities in the leaves of two cultivars. For the PR proteins and defense enzymes in stems, the combination of elevated [CO2] and elevated temperature obviously increased the catalase (CAT), phenylalanine ammonia-lyase (PAL), β-1, 3-glucanase (GLU) or superoxide dismutase (SOD) activities for both Lemont and YSBR1. For different cultivars, after being infected with R. solani, the activities of PR proteins and defense enzymes in the leaves and SOD and CAT in the stems for YSBR1 were significantly higher than those for Lemont under different treatments, and the development rate of ShB lesion for YSBR1 was significantly lower than that for Lemont. During the whole disease infection, elevated [CO2] and the combination of elevated [CO2] and elevated temperature both significantly increased the development rate of rice ShB for Lemont by 21%-45%, but not for YSBR1. The correlation analysis showed that under different [CO2] and temperature treatments, the development rate of ShB was significantly positively correlated with GLU activity in stems for Lemont and YSBR1.【Conclusion】After inoculated R.solani, the defense reaction formed by PR proteins and defense enzymes in resistant cultivar can effectively reduce the effect of elevated [CO2] and temperature on the development rate of ShB in the future. This study can provide applications for breeding ShB-resistant cultivars to ensure global rice production under future climate change.