Abstract:Tobacco is a warm-loving crop that is sensitive to low temperatures. During the floating seedling stage, it is vulnerable to adverse effects from cold spells such as “late spring cold” and low light. To address the issues of slow growth and reduced survival rate of tobacco seedlings caused by such cold spells, this study explored the colonization effect of the endophytic fungus Piriformospora indica in tobacco roots and its mechanism for enhancing tobacco cold resistance without altering the current floating seedling cultivation method. The results showed that the colonization of P. indica in the roots of tobacco seedlings significantly increased the activity of the antioxidant enzyme system, including SOD, CAT, POD, and APX, in tobacco, effectively curbing the excessive accumulation of reactive oxygen species (ROS). Additionally, P. indica promoted the accumulation of osmotic adjustment substances in tobacco, including soluble sugars, proline, and soluble proteins. Moreover, Piriformospora indica could further stimulate the expression of cold response genes and enhance the photosynthetic capacity of tobacco by promoting chlorophyll synthesis and the efficiency of photosystem II (PSII). This study clarified the multi-pathway mechanism by which P. indica enhances tobacco cold resistance and provided an effective strategy for promoting the growth of tobacco seedlings under low temperature.
