Effects of Exogenous Melatonin on Disease Resistance of Potato under Late Blight Stress

doi:10.13560/j.cnki.biotech.bull.1985.2025-1425

Abstract

Abstract:

Objective Melatonin (MT) acts as a crucial signaling molecule in plant responses to biotic and abiotic stresses, its physiological effects exhibit a significant dose-response relationship. To investigate the impact and underlying mechanism of exogenous MT on potato late blight, and to identify the optimal concentration for suppressing Phytophthora infestans (P. infestans) infection, this study provides a theoretical foundation for the potential field application of MT. Methods Using the potato cultivar ‘Qingshu 9’ as material, different concentrations of MT (0, 300, 650, 1 300, 1 650, and 2 000 μmol/L) were sprayed on leaves continuously for three days (morning, noon, and evening) before inoculation with P. infestans. After pathogen infection, the control efficacy, antioxidant system, defense enzyme activities, and defense-related gene expression in potato plants were analyzed. Results Exogenous MT effectively inhibited the mycelial growth of P. infestans. MT concentrations ranging from 300 to 2 000 μmol/L enhanced the resistance of potato to late blight, with 1 300 μmol/L was identified as the optimal concentration based on DAB and trypan blue staining. Compared to the control, pretreatment with 1 300 μmol/L MT increased the activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX), while reducing the accumulation of reactive oxygen species and malondialdehyde (MDA). Additionally, it enhanced the activities of defense-related enzymes such as chitinase (CHT), polyphenol oxidase (PPO), peroxidase (POD), and phenylalanine ammonia-lyase (PAL), and significantly induced the expression of defense genes (StPR1, StPR5, StPOD, and StPPO). Conclusion Under P. infestans stress, MT treatment enhances potato resistance to late blight by inhibiting pathogen mycelial growth, improving the plant antioxidant capacity, activating defense enzyme activities, and inducing the expression of defense genes.

Key words: melatonin, potato, late blight, disease resistance, antioxidant capacity

WANG Bing-bing, ZHU Di, YANG Sheng-long, LI Yi-lin, YANG Qi, HE Miao-miao. Effects of Exogenous Melatonin on Disease Resistance of Potato under Late Blight Stress[J]. Biotechnology Bulletin, 2026, 42(6): 107-115.

Figures/Tables 7

Fig. 1 Effects of different concentrations of MT on the growth of P. infestansA: P. infestans mycelial growth phenotype. B: Mycelium growth inhibition rate. CK: Control; MT: Melatonin; Different lowercase letters indicate significant differences at the 0.05 level. The same below

Fig. 2 Indoor efficacy of different concentrations of MT against potato late blightA: Control group. B: Melatonin-pretreated group

Fig. 3 Induced resistance effect of potato plants to P. infestans 7 days after inoculation with different concentrations of MT

Fig. 4 In vivo histochemical staining phenotypes of DAB and trypan blueA: DAB staining of leaves. B: DAB staining of infected sites under electron microscopy. C: Trypan blue staining of leaves. D: Trypan blue staining of infected sites under electron microscopy

Fig. 5 Effect of melatonin pretreatment on defense enzyme activities and malondialdehyde content in potato following inoculation with P. infestans

Fig. 6 Effect of melatonin pretreatment on the antioxidant system of potato after inoculation with P. infestans

Fig. 7 Effect of MT pretreatment on defense gene expression in potato following inoculation with P. infestans

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