Sporisorium scitamineum colonisation of sugarcane genotypes susceptible and resistant to smut revealed by GFP‐tagged strains

Abstract

Sporisorium scitamineum is the causal agent of sugarcane smut disease. The fungus establishes a biotrophic interaction with sugarcane tissues, and unlike smut fungi of other monocot hosts, the primary meristem of sugarcane plants develops a whip-like structure instead of a tumour-like galls emerging from floral structures (tassels and ears). We examined (GFP)-tagged S. scitamineum infecting tissues of three sugarcane genotypes with distinct responses to smut (susceptible, intermediate resistant and resistant). Mating compatible haploid cells gfp-expressing were obtained by Agrobacterium tumefaciens-mediated transformation (ATMT) using the integrative vector pFAT-gfp. Regardless of the inoculation method (drop inoculation and hypodermal syringe inoculation), all genotypes were colonised by the fungus. GFP-tagged strains of opposite mating reaction were able to: (a) grow in vitro as fluorescent yeast-like cells; (b) generate infectious dikaryon; (c) penetrate sugarcane tissues; (d) colonise tissues by growing a filamentous network; and (e) form the characteristic highly branched hyphae within host cells. Fungal colonisation 160 DAI revealed an association of the fungus with vascular vessels disrupting their organisation in all three genotypes analysed. However, the resistant plants did not develop whips spanning the experiment time. The first whips emerged 76 DAI from plants of the susceptible genotype whereas for intermediate resistant plants whips were detected at 137 DAI. These whips were dissected and fluorescent sporogenesis and teliospore maturation were analysed. In vitro germination of recovered teliospores revealed after meiosis the formation of a three-celled hyphal filament, where the fourth cell was likely maintained in the teliospore coat. These cells showed independent segregation of the gfp marker, as a result of gfp insertions in different chromosomes of each compatible haploid strain. This work presents the complete fungal life cycle of GFP-marked S. scitamineum to study developmental stages in planta.

Control of Sugarcane Smut Disease Incited by Sporisorium scitamineum Syd. Using Peroxyacetic Acid (PAA)

“…It was reported that severe smut outbreak in the Caribbean has created an impact amongst cane growers and sugar industry. Consequently, the plantations are undertaking different smut management practices such as continued monitoring and rouging of smut affected stools, hot water treatment (at 50°C for 2 hours for initial seed cane nursery) of seed sets, chemical treatment of sets, use of resistant varieties, and avoidance of ratooning of affected fields (Abdou et al, 1990;Wada et al, 1999;Abera et al, 2009;Firehunet al, 2009;Mansour et al, 2016;Carvalho et al, 2016;Sánchez-Elordi et al, 2016 andLiu et al, 2017) Due to their core role in plant health, reactive oxygen species (ROS) and antioxidants Sutherland (1991) and Levine et al (1994) have shown a major role in plant pathogen interactions (Galal and Abdou, 1996;Adam et al, 2000;EL-Ashmony et al, 2017). Both acetic acid and hydrogen peroxide reacted as bactericides and fungicides against many phytopathogenic bacteria and fungi (Narcisoet al, 2007 andOsórioet al, 2013;Ayoub et al, 2017 and).…”

Study of sugarcane metabolism modulation by the plant pathogenic fungus <em>Sporisorium scitamineum</em>

“…Up-regulation of energy-related pathways is a conserved response to demands of biotic stresses, such as the synthesis of secondary metabolites (Less et al, 2011;Rojas et al, 2014). Even in sugarcane genotypes resistant to smut, i. e. those that do not emit whip, S. scitamineum colonization is detected (Carvalho et al, 2016) potentially interfering with carbon allocation. In addition, increased energetic metabolism network may also imply that stems reduce sucrose accumulation, one of the smut susceptible symptoms yet not investigated in resistant genotypes colonized by smut.…”

“…M. Piepenbr., M. Stoll & Oberw is the causal agent of sugarcane smut, one of the major diseases that affect the culture worldwide (Sundar et al, 2015), featuring a biotrophic lifestyle with inter-or intracellular growth (Carvalho et al, 2016;Stoll et al, 2005). The presence of the fungus in the plant leads to the development of a long structure like a "whip" in susceptible varieties at the apex of the apical or lateral meristems (Figure 1A, B;Sundar et al, 2012).…”

“…Resistance to smut is based in a scale that ranges from 0 (Immune) to 9 (very highly susceptible) (Latiza et al, 1980). However, varieties classified as resistant by this approach may suddenly develop whips, according to environmental conditions, since the pathogen is able to colonize sugarcane tissues of resistant varieties (Carvalho et al, 2016).…”

“…Piepenbr., M. Stoll & Oberw is the causal agent of sugarcane smut, one of the major diseases that affect the culture in the world (Sundar et al, 2015), featuring a biotrophic lifestyle with inter-or intracellular growth (Stoll et al, 2005). GFPfusioned mutants of S. scitamineum infecting tissues of sugarcane genotypes with distinct response to smut evidenced its growth even in the resistant varieties and disrupted organization of vascular vessels (Carvalho et al, 2016).…”