title: Exogenous Trehalose Treatment Enhances the Activities of Defense-Related Enzymes and Triggers Resistance against Downy Mildew Disease of Pearl Millet.
abstract: In recent years, diverse physiological functions of various sugars are the subject of investigations. Their roles in signal transduction in plant responses to adverse biotic and abiotic stress conditions have become apparent, and growing scientific evidence has indicated that disaccharides like sucrose and trehalose mediate plant defense responses in similar way as those induced by elicitors against the pathogens. Trehalose is a well-known metabolic osmoregulator, stress-protectant and non-reducing disaccharide existing in a variety of organisms, including fungi, bacteria, and plants. Commercially procured trehalose was applied to seeds of susceptible pearl millet (Pennisetum glaucum) cultivar "HB3," and tested for its ability to reduce downy mildew disease incidence by induction of resistance. Seed treatment with trehalose at 200 mM for 9 h recorded 70.25% downy mildew disease protection, followed by those with 100 and 50 mM trehalose which offered 64.35 and 52.55% defense, respectively, under greenhouse conditions. Furthermore, under field conditions treatment with 200 mM trehalose for 9 h recorded 67.25% downy mildew disease protection, and reduced the disease severity to 32.75% when compared with untreated control which displayed 90% of disease severity. Trehalose did not affect either sporangial formation or zoospore release from sporangia, indicating that the reduction in disease incidence was not due to direct inhibition but rather through induction of resistance responses in the host. Additionally, trehalose was shown to enhance the levels of polyphenol oxidase, phenylalanine ammonia lyase, and peroxidase, which are known as markers of both biotic and abiotic stress responses. Our study shows that osmoregulators like trehalose could be used to protect plants against pathogen attacks by seed treatment, thus offering dual benefits of biotic and abiotic stress tolerance.
authors.affiliation: Department of Studies and Research in Environmental Science, Centre for Bioinformation, Tumkur University Tumkur, India.
authors.forename: Sharathchandra R
authors.initials: SR
authors.lastname: Govind
authors.affiliation: Plant Healthcare and Diagnostic Center, Department of Studies in Biotechnology and Microbiology, Karnatak University Dharwad, India.
authors.forename: Sudisha
authors.initials: S
authors.lastname: Jogaiah
authors.affiliation: Graduate School of Life Sciences, Tohoku UniversitySendai, Japan; Department of Botany, Faculty of Science, Aswan UniversityAswan, Egypt.
authors.forename: Mostafa
authors.initials: M
authors.lastname: Abdelrahman
authors.affiliation: Downy Mildew Research Laboratory, Department of Studies in Biotechnology, University of Mysore Mysore, India.
authors.forename: Hunthrike S
authors.initials: HS
authors.lastname: Shetty
authors.affiliation: Plant Abiotic Stress Research Group & Faculty of Applied Sciences, Ton Duc Thang UniversityHo Chi Minh City, Vietnam; Signaling Pathway Research Unit, RIKEN Center for Sustainable Resource ScienceYokohama, Japan.
authors.forename: Lam Son P
authors.initials: LS
authors.lastname: Tran
keywords: downy mildew; induction of resistance; pearl millet; stress responses; trehalose