Arbuscular Mycorrhizal Fungi Inoculation to Enhance Chilling Stress Tolerance of Watermelon

In this study the positive effects of Glomus intraradices symbiosis on growth, physiological and biochemical attributes of watermelon (Citrullus lanatus) cv. Crimson Sweet and Charleston Gray in response to chilling stress were investigated. When subjected to chilling stress, arbuscular mycorrhizal fungi (AMF)-inoculated watermelon seedlings exhibited significantly higher root and shoot dry mass than non-AMF-inoculated plants. AMF symbiosis also improved chilling stress in watermelon seedlings via alterations in chlorophyll content and photosynthesis efficiency. Notably, AMF inoculation resulted in reduced chilling-induced oxidative stress evident by significantly decreased accumulation of H2O2 and malondialdehyde (MDA). Chilling stress enhanced leaf electrolyte leakage of watermelon seedlings, while inoculation of AMF significantly ameliorated electrolyte leakage by 9.91 and 11.58% in Crimson Sweet and Charleston Gray, respectively, under 36& x202f;h of chilling stress. AMF symbiosis combined with 36& x202f;h chilling stress significantly induced peroxidase (POX) activity (1.26- and 1.17-fold in Crimson Sweet and Charleston Gray, respectively) compared with non-AMF-inoculated seedlings. These results indicate that AMF symbiosis could play an important role in improving chilling resistance of watermelon seedlings by restoring photosynthesis efficiency and relieving chilling-induced oxidative stress.