Endophytic microbes enhance sugarcane defense against Sporisorium scitamineum by activating calcium signaling and stress-responsive traits

Sugarcane, a widely grown crop, faces many challenges from pests, diseases, and environmental stresses. One of the most serious threats is smut disease, caused by the fungus Sporisorium scitamineum (SS). Although there are methods to control it, managing this disease effectively is still a big challenge. This study evaluates the synergistic application of endophytic bacteria Bacillus sp. QN2MO-1 (BS) and Pseudomonas chlororaphis (PS) as a biocontrol approach to combat smut disease. Two sugarcane cultivars, ROC22 and Zhongtang 3, were initially grown in pots and later relocated to field conditions. Endophyte applications and SS infection were validated using qRT-PCR. A detailed assessment was conducted on physiological and morphological parameters, antioxidant enzyme activities, stress indicators, and the expression of stress-responsive genes. Results demonstrated that BS and PS, either individually or combined, effectively suppressed smut disease. Enhanced expression of defense-related genes (ScCAT1, SOD1 and PR1.04). Increased antioxidant enzyme activities (SOD, CAT, POD) were observed, particularly in the resistant cultivar Zhongtang 3. Elevated levels of salicylic acid (SA) and jasmonic acid (JA) indicated the activation of stress-related pathways, enhancing defense mechanisms. Endophyte-treated plants exhibited maximum growth and photosynthetic rates. Conversely, reduced malondialdehyde (MDA) and hydrogen peroxide (H₂O₂) levels suggested mitigation of oxidative stress. In the case of CAMTAs genes expression profiling, SsnpCAMTA5 upregulated in both cultivars, SsnpCAMTA7, SsnpCAMTA8 upregulated in Zhongtang 3. SsnpCAMTA12 downregulated in only Zhongtang 3 both time points (30 and 60 dpi). This result suggest that the bacterial endophytes triggered the pathogens related genes. These findings emphasize the potential of BS and PS as a sustainable, innovative biocontrol strategy, offering a promising solution to enhance sugarcane resilience and mitigate smut disease through integrated biological approaches.