The arbuscular mycorrhiza fungusRhizophagus irregularisMUCL 41833 decreases disease severity of Black Sigatoka on banana c.v. Grande naine, underin vitroculture conditions

Abstract

Introduction. Mycosphaerella fijiensis, the fungal pathogen causing Black Sigatoka disease, attacks almost all cultivars of bananas and plantains. Currently, the repeated application of fungicides is the most widespread control measure, while the use of bio-control agents remains almost ignored. Here we investigated, under in vitro culture conditions, whether an arbuscular mycorrhizal fungus (AMF-Rhizophagus irregularis MUCL 41833) could reduce the severity of disease caused by M. fijiensis MUCL 47740 on banana. Materials and methods. Prior to their transfer to autotrophic in vitro culture systems and subsequent inoculation by the pathogen, the banana plantlets cultivar Grande Naine (AAA genome Cavendish group) were grown in the extra-radical mycelium network of the AMF, arising from Medicago truncatula plantlets, for fungal root colonization. Results and discussion. At the time of infection with M. fijiensis, the AMF colonization of the banana plantlets was 12%, 56% and 10% for hyphae, arbuscules and spores/vesicles, respectively, and the number of spores produced in the medium was above 200. At day 21 and day 35 following infection by the pathogen, the number of extra-radical spores as well as the abundance of arbuscules in roots, were significantly higher than in the non-infected plantlets. Conversely, the severity index measured in the mycorrhizal plantlets decreased by more than 80% and 60%, respectively, 21 and 35 days after infection by the pathogen. Similarly, the area under disease progress curve, estimated at day 35, was reduced by 59% in the mycorrhizal banana plantlets as compared to the control plantlets. Whatever the treatment (mycorrhizal or non mycorrhizal plantlets in presence/absence of M. fijiensis), no significant differences were observed in plantlet dry weight, pseudostem height and diameter, and leaf area at both observation times. Conclusions. These results emphasize the complex multitrophic interactions between above and below-ground microorganisms mediated via the plant. They further suggest that AMF may decrease, at least at the early stage of infection, M. fijiensis symptoms possibly via the induction of a systemic resistance pathway. The important decrease in symptoms observed in the mycorrhizal banana plantlets suggest that these microorganisms may represent a potentially attractive option to consider in the context of an integrated control of this important disease. Keywords: banana / Musa accuminata / vesicular arbuscular mycorrhizae / Mycosphaerella fijiensis / Rhizophagus irregularis / disease control method / in vitro culture Résumé-Le champignon mycorhizien à arbuscules Rhizophagus irregularis MUCL 41833 décroît la sévérité de la maladie des raies noires chez le bananier c.v. Grande naine en conditions de culture in vitro. Introduction. Mycosphaerella fijiensis, le champignon responsable de la maladie des raies noires, s'attaque à la grande majorité des cultivars de bananiers et plantains. À l'heure actuelle, l'application répétée de fongicides est la principale mesure de contr...

Rhizophagus irregularis and Rhizoctonia solani Differentially Elicit Systemic Transcriptional Expression of Polyphenol Biosynthetic Pathways Genes in Sunflower

“…Rhizophagus irregularis (Błaszk., Wubet, Renker & Buscot) C. Walker & A. Schüßler 2010 (former Glomus intraradices) is an obligate biotrophic arbuscular mycorrhizal fungus that belongs to phylum: Mucoromycota, subphylum: Glomeromycotina, class: Glomeromycetes [8], and forms mutualistic symbioses with various plant species [9]. Several beneficial effects have been widely reported as a result of this relationship, including the enhancement of plant growth, nutrient and water transport, improvement of heavy metal, salinity, and drought tolerance, and the induction of plant disease resistance [10][11][12][13]. In this regard, El-Sharkawy et al [14] reported a significant reduction in the stem rust of wheat, which is caused by Puccinia graminis Pers.…”

Increased Silicon Acquisition in Bananas Colonized by Rhizophagus irregularis MUCL 41833 Reduces the Incidence of Pseudocercospora fijiensis

“…Increased biomass was often reported in banana plants colonized by AMF (Declerck et al, 1995; Oye Anda et al, 2015). This increase was usually attributed to the capacity of the extraradical AMF mycelium network to take up, translocate and transfer high amounts of nutrients (e.g., P) to the host plant cortical cells via arbuscules in exchange for photosynthates.…”

“…The strain was then transferred onto V8 juice agar medium (Erwin and Ribeiro, 1996) in Petri plates (90 mm diam.) for another 2 weeks under continuous light (PPF of 60–65 μmol m -2 s -1 ) at 22°C for mycelium and spores production (Oye Anda et al, 2015). The mycelium was then scrapped from the culture medium, grinded in 10 ml of sterile water with a mortar and pestle and passed through sterile cheesecloth (one-layer pore size of approximately 150 μm) to separate the mycelium from conidia.…”

“…Several studies have reported their role in the reduction of incidence and/or severity of soil-borne as well as leaf pathogens (Jung et al, 2012). In banana, they have been shown to decrease the incidence of nematodes such as Radopholus similis (Koffi et al, 2013) and Pratylenchus goodeyi (Elsen et al, 2003) and fungal pathogens such as Cylindrocladium spathiphylli (Declerck et al, 2002), Fusarium oxysporum var cubense (Jaizme-Vega et al, 1997) and more recently M. fijiensis (Oye Anda et al, 2015).…”

Impact of arbuscular mycorrhizal fungus (<i>Rhizophagus irregularis</i>) on disease symptoms caused by the ascomycete fungus (<i>Mycosphaerella fijiensis M.</i>) in Black Sigatoka-resistant banana plantain

“…Increased resistance was observed in tomato against Alternaria solani (Fritz et al, 2006) and Botrytis cinerea (Jung et al, 2009); in cucumber against Colletotrichum orbiculare (Lee et al, 2005) and in potato against Phytophthora infestans (Gallou et al, 2011). Recently, Oye Anda et al, (2015) demonstrated under in vitro culture conditions that pre-mycorrhized banana (cv. Grande naine) plantlets had reduced leaf-spot disease symptoms caused by M. fijiensis compared to non-mycorrhized plants.…”