title: Salicylic acid confers enhanced resistance to Glomerella leaf spot in apple.
abstract: Glomerella leaf spot (GLS) caused by Glomerella cingulata is a newly emergent disease that results in severe defoliation and fruit spots in apple. Currently, there are no effective means to control this disease except for the traditional fungicide sprays. Induced resistance by elicitors against pathogens infection is a widely accepted eco-friendly strategy. In the present study, we investigated whether exogenous application of salicylic acid (SA) could improve resistance to GLS in a highly susceptible apple cultivar (Malus domestica Borkh. cv. 'Gala') and the underlying mechanisms. The results showed that pretreatment with SA, at 0.1-1.0 mM, induced strong resistance against GLS in 'Gala' apple leaves, with SA treated leaves showing significant reduction in lesion numbers and disease index. Concurrent with the enhanced disease resistance, SA treatment markedly increased the total antioxidant capacity (T-AOC) and defence-related enzyme activities, including catalase (CAT), superoxide dismutase (SOD), peroxidase (POD), phenylalanine ammonia-lyase (PAL) and polyphenol oxidase (PPO). As expected, SA treatment also induced the expression levels of five pathogenesis-related (PR) genes including PR1, PR5, PR8, Chitinase and β-1,3-glucanase. Furthermore, the most pronounced and/or rapid increase was observed in leaves treated with SA and subsequently inoculated with G. cingulata compared to the treatment with SA or inoculation with the pathogen. Together, these results suggest that exogenous SA triggered increase in reactive oxygen species levels and the antioxidant system might be responsible for enhanced resistance against G. cingulata in 'Gala' apple leaves.
authors.affiliation: College of Agronomy and Plant Protection, Key Lab of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, PR China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: College of Agronomy and Plant Protection, Key Lab of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, PR China.
authors.forename: Xiangpeng
authors.initials: X
authors.lastname: Shi
authors.affiliation: College of Agronomy and Plant Protection, Key Lab of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, PR China.
authors.forename: Baohua
authors.initials: B
authors.lastname: Li
authors.affiliation: College of Chemistry and Pharmaceutical Sciences, Qingdao Agricultural University, Qingdao, 266109, PR China.
authors.forename: Qingming
authors.initials: Q
authors.lastname: Zhang
authors.affiliation: College of Agronomy and Plant Protection, Key Lab of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, PR China.
authors.forename: Wenxing
authors.initials: W
authors.lastname: Liang
authors.affiliation: College of Agronomy and Plant Protection, Key Lab of Integrated Crop Pest Management of Shandong Province, Qingdao Agricultural University, Qingdao, 266109, PR China. Electronic address: cxwang@qau.edu.cn.
authors.forename: Caixia
authors.initials: C
authors.lastname: Wang
mesh_terms: D000975:Antioxidants / Q000378:metabolism; D002374:Catalase / Q000378:metabolism; D004156:Catechol Oxidase / Q000378:metabolism; D002688:Chitinases / Q000235:genetics / Q000378:metabolism; D060467:Disease Resistance / Q000187:drug effects*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D006026:Glycoside Hydrolases / Q000235:genetics / Q000378:metabolism; D006861:Hydrogen Peroxide / Q000378:metabolism; D027845:Malus / Q000187:drug effects / Q000235:genetics / Q000276:immunology* / Q000382:microbiology*; D010544:Peroxidases / Q000378:metabolism; D010650:Phenylalanine Ammonia-Lyase / Q000378:metabolism; D020081:Phyllachorales / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D010935:Plant Diseases / Q000382:microbiology*; D018515:Plant Leaves / Q000187:drug effects / Q000201:enzymology / Q000382:microbiology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D060888:Real-Time Polymerase Chain Reaction; D020156:Salicylic Acid / Q000494:pharmacology*; D013482:Superoxide Dismutase / Q000378:metabolism
chemical_list: D000975:Antioxidants; D012333:RNA, Messenger; D006861:Hydrogen Peroxide; D004156:Catechol Oxidase; D010544:Peroxidases; D002374:Catalase; D013482:Superoxide Dismutase; D006026:Glycoside Hydrolases; D002688:Chitinases; D010650:Phenylalanine Ammonia-Lyase; D020156:Salicylic Acid
keywords: Defence-related enzyme; Glomerella cingulata; Induced resistance; Malus domestica Borkh. cv. ‘Gala’; Pathogenesis-related protein; Salicylic acid