A non-native pathogen meets a native host: Austropuccinia psidii infection reduces photosynthesis and alters non-structural carbohydrates in seedlings of Metrosideros excelsa

{"title":"A non-native pathogen meets a native host: Austropuccinia psidii infection reduces photosynthesis and alters non-structural carbohydrates in seedlings of Metrosideros excelsa","authors":"Hoa Nguyen,&nbsp;Peter J. Bellingham,&nbsp;Mahajabeen Padamsee,&nbsp;Luitgard Schwendenmann","doi":"10.1007/s00468-024-02593-8","DOIUrl":null,"url":null,"abstract":"<div><h3>Key message</h3><p><i>Austropuccinia psidii</i> infection and increase in diseased leaf area resulted in a reduction of photosynthesis, an upregulation of stomatal conductance, and an increase in leaf starch and sucrose content.</p><h3>Abstract</h3><p><i>Austropuccinia psidii</i> is a biotrophic rust pathogen that causes myrtle rust, affecting over 480 species in the Myrtaceae family. The development of chlorotic and necrotic leaf areas following <i>A. psidii</i> infection has been shown to affect leaf gas exchange. In this study, we quantified photosynthesis, stomatal conductance, and non-structural carbohydrates in seedlings of a long-lived tree, <i>Metrosideros excelsa</i> (pōhutukawa), following <i>A. psidii</i> infection in a glasshouse experiment (infected and control seedlings) conducted over 20 weeks. The diseased leaf area rose from 8% in week 2 to 95% in week 20 after <i>A. psidii</i> inoculation. The photosynthetic rate declined by over 90% within 6 weeks after inoculation and was associated with biochemical damage in CO₂ fixation. Stomatal conductance decreased over the first 4 weeks after inoculation and then increased. An increase in lesions and necrotic cells may inhibit stomatal regulation. Starch content was threefold higher in infected than control leaves 20 weeks after inoculation. Increased starch accumulation in the infected leaf area could be due to reduced export of newly fixed carbon from the infected leaves. Meanwhile, glucose + fructose content was 31% lower in infected leaves at the experiment’s end, likely because of leaf necrosis. If the pathogen-induced damage and loss of leaves, reduction in photosynthesis and changes in non-structural carbohydrates shown in this study also occur in wild <i>M. excelsa</i> seedlings and reduces their biomass, this may in turn reduce their competitive ability in the primary successions that they currently often dominate.</p></div>","PeriodicalId":805,"journal":{"name":"Trees","volume":"39 1","pages":""},"PeriodicalIF":2.1000,"publicationDate":"2025-01-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://link.springer.com/content/pdf/10.1007/s00468-024-02593-8.pdf","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Trees","FirstCategoryId":"2","ListUrlMain":"https://link.springer.com/article/10.1007/s00468-024-02593-8","RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"FORESTRY","Score":null,"Total":0}