Abstract
The root-endophytic fungus Piriformospora indica (=Serendipita indica) has been revealed for its growth-promoting effects and its capacity to induce resistance in a broad spectrum of host plants. However, the bioefficacy of this fungus had not yet been tested against any pathogen affecting onion (Allium cepa). In this study, the biocontrol potency of P. indica against onion leaf blight, an impacting disease caused by the necrotrophic fungal pathogen Stemphylium vesicarium, was evaluated. First, it was proved that colonisation of onion roots by P. indica was beneficial for plant growth, as it increased leaf development and root biomass. Most relevantly, P. indica was also effective in reducing Stemphylium leaf blight (SLB) severity, as assessed under greenhouse conditions and confirmed in field trials in two consecutive years. These investigations could also provide some insight into the biochemical and molecular changes that treatment with P. indica induces in the main pathways associated with host defence response. It was possible to highlight the protective effect of P. indica colonisation against peroxidative damage, and its role in signalling oxidative stress, by assessing changes in malondialdehyde and H2O2 content. It was also showed that treatment with P. indica contributes to modulate the enzymatic activity of superoxide dismutase, catalase, phenylalanine ammonia-lyase and peroxidase, in the course of infection. qPCR-based expression analysis of defence-related genes AcLOX1, AcLOX2, AcPAL1, AcGST, AcCHI, AcWRKY1, and AcWRKY70 provided further indications on P. indica ability to induce onion systemic response. Based on the evidence gathered, this study aims to propose P. indica application as a sustainable tool for improving SLB control, which might not only enhance onion growth performance but also activate defence signalling mechanisms more effectively, involving different pathways.
Highlights
IntroductionSimmons [1] is the most common destructive foliar fungal disease of onion (Allium cepa) worldwide [2–5]
We have evaluated the efficacy of the beneficial fungal endophyte P. indica against the harmful Stemphylium leaf blight (SLB) disease associated with S. vesicarium infection in onions
We have been interested in providing an initial and overall assessment of biochemical and molecular markers that could prove the indirect effect elicited by P. indica on the response of onion to the infection by S. vesicarium
Summary
Simmons [1] is the most common destructive foliar fungal disease of onion (Allium cepa) worldwide [2–5]. Besides onion, this pathogen infects a wide range of other economically important crops such as garlic (Allium sativum) [6], chilli pepper (Capsicum annuum) [7], leek (Allium ampeloprasum) [6], asparagus (Asparagus officinalis) [8], pear (Pyrus communis) [9,10], and mango (Mangifera indica) [11]. [6], chilli pepper (Capsicum annuum) [7], leek (Allium ampeloprasum) [6], asparagus (Asparagus officinalis) [8], pear (Pyrus communis) [9,10], and mango (Mangifera indica) [11]. BTy) p[1ic2a].llTyy, SpLicBalolycc, uSrL-B oreccnucerrebnecceombeecsoemveids eenvtidaesntthaes pthlaenptlacnotmceosmteos mtoamtuartiutyritayndantdhethleealefasfesneensecsecnecneceprporcoecsesss bbeeggiinnss. SSyymmppttoommssininitiitaialllylylilmimitietdedtotochcahraarcatcetreisrtiisctiyceylleolwloiwshis,hw, awteart-esro-askoeadkesdpostpsoptsropgrroe-ss rgarpeisdslyraapsidthlye apsatthhoegpeanthcoogmemn ecnocmems teonrceelseatoserietlsesapseorietss.sTphoerelse.aTvhees tlheaevnebsetghienntobedgeivnetloop ldeesvioenlospthleastiboencsotmhaet pbreocogmreesspivroelgyremssoivreeleyxmteonrseiveex,tuennstiivl eth, euyntciol athleesycecoaanldesrceesaunltdinrelsaurlgte nineclraorgseesntehcartocsaesntlheaatdctaoncloeamdptloetceolmeapfledteesliecacfadtieosnicacnadtiopnlaanntddpelaatnht[d1e3a]t(hFi[g1u3]re(F1i)g.ure 1)
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