Responses of root physiological characteristics and resistance gene expression to infection by Meloidogyne incognita at different temperatures in tobacco

Zhixiao Yang¹Qilong Chen²Rengang Wang¹Yingchao Lin¹Dejun Kong¹Zhihong Wang¹Xiner He³Zhujun Han⁴Yushuang Guo^1*Haiqian Xia^1*Yi Cao¹

• ¹Other
• ²Henan Provincial Tobacco Company, Luohe, China
• ³China Tobacco Hunan Industrial Company, Changsha, China
• ⁴Jiangxi Tobacco Company, Jian, China

In the present research, to further explore the resistance mechanism of M. incognita influenced by temperature. The antioxidant enzyme activities, osmotic regulation substance contents, tissue structure changes, and resistance gene (Rk) expression characteristics in the roots of different tobacco varieties at three temperatures (15°C, 25°C, and 35°C) were analyzed, and a M. incognita-resistant variety (NC95) and susceptible one (CBH) was selected as the research materials. The results showed the activities of peroxidase (POD) and catalase (CAT) and the contents of soluble sugar, proline, and hydroxyproline-rich glycoprotein (HRGP) increased by different degrees under infection, while the superoxide dismutase (SOD) activity decreased. The activities of POD and CAT and the contents of soluble sugar, proline, and HRGP in NC95 were all higher than in CBH. Meanwhile, the antioxidant enzyme activities and osmotic substance contents in both varieties varied the most at 25°C and the least at 35°C, respectively. There were no giant cells and oocysts observed in the root tissue structure of NC95 under infection at different temperatures, but a large number of giant cells and oocysts appeared in CBH. The number of giant cells in CBH at 25°C was more than that at 15°C and 35°C, respectively, and the lignification degree in NC95 was also more severe at 25°C. In addition, the expression of Rk gene in NC95 was promoted by M. incognita infection, and the expression levels at 25°C and 15°C were higher than at 35°C, respectively. Research indicated that the SOD activity and osmotic regulation substance contents reduced in the roots of susceptible variety under M. incognita infection, and a large number of giant cells appeared in the xylem, thus resulting in the susceptibility. On the contrary, the resistant tobacco variety showed stronger abilities in reactive oxygen species (ROS) scavenging and osmotic regulation, no significant changes in root tissue structure, and the up-regulated expression of Rk gene, which were conducive to inhibiting infection. Compared with the appearances at 25°C, the M. incognita infectivity on tobacco roots was effectively lowered by increasing the antioxidant enzyme activities and osmotic regulation substance contents and maintaining good root tissue structure at 35°C.