Detection of isometric, dsRNA-containing viral particles in Colletotrichum gloeosporioides isolated from cashew tree

Abstract

Fungi are disease-causing agents in plants and affect crops of economic importance. One control method is to induce resistance in the host by using biological control with hypovirulent phytopathogenic fungi. Here, we report the detection of a mycovirus in a strain of Colletotrichum gloeosporioides causing anthracnose of cashew tree. The strain C. gloeosporioides URM 4903 was isolated from a cashew tree (Anacardium occidentale) in Igarassu, PE, Brazil. After nucleic acid extraction and electrophoresis, the band corresponding to a possible double-stranded RNA (dsRNA) was purified by cellulose column chromatography. Nine extrachromosomal bands were obtained. Enzymatic digestion with DNAse I and Nuclease S1 had no effect on these bands, indicating their dsRNA nature. Transmission electron microscopic examination of extracts from this strain showed the presence of isometric particles (30-35 nm in diameter). These data strongly suggest the infection of this C. gloeosporioides strain by a dsRNA mycovirus. Once the hypovirulence of this strain is confirmed, the strain may be used for the biological control of cashew anthracnose. Key words: Anacardium occidentale, anthracnose, biological control, hypovirulence, mycovirus, phytopathogenic fungi.Fungi are the most important disease-causing agents in plants with serious economic impact. Chemical methods to control phytopathogenic fungi can affect human health and have environmental consequences. In an attempt to minimize dependence on chemical methods, alternative means of pathogen control have been investigated (Yu et al., 2010). One alternative is to use hypovirulent phytopathogenic fungal strains that can biologically control phytopathogenic fungi of the same or related species. Fungal hypovirulence is usually caused by mycoviral infection. Hypovirulent fungi cause milder infection and may induce hypovirulence in other pathogenic strains via viral transfer (Pearson et al., 2009).All currently known mycoviruses have isometric, double-stranded RNA (dsRNA)-containing particles, and are classified into three families: Chrysoviridae, Endornaviridae, Partitiviridae and Totiviridae. Particle size ranges from 25 to 50 nm in diameter, except for endornaviruses which do not produce virions (Chu et al., 2002;Ghabrial & Suzuki, 2009).In this communication, we report the presence of isometric dsRNA viral particles in a strain of Colletotrichum gloeosporioides (Penz.) Sacc., the causal agent of anthracnose in cashew tree.Colletotrichum gloeosporioides URM 4903 was isolated from anthracnose lesions on a cashew tree (Anacardium occidentale L.) in the town of Igarassu, Pernambuco, Brazil (7°50'3.74"S and 34°54'22.87"O), and deposited in the mycology collection (URM) at Federal University of Pernambuco, Recife, PE. This strain was chosen after preliminary tests revealed poor pathogenicity in detached cashew leaves and the presence of extrachromosomal bands in agarose gel electrophoresis (unpublished data).PDA (20% potato extract, 2% dextrose, 1.5% agar) and PD (20% potato extract,...

RNA applications for endophytic research

“…Previous results indicate that the virulence of the fungal species may be related to mycovirus infection. Since other studies have reported similar results (Dalzoto et al, 2006;Figueirêdo et al, 2012;Zhong et al, 2014) and taking the behavior into consideration, mycoviruses may be considered a biocontrol tool against pathogen virulence.…”

Investigating variability and behaviour of Colletotrichum gloeosporioides strains from lesions of coffee blister spot

“…Literature information shows the existence of interactions among fungus, viruses and host plants (Lamichhane & Venturi, ; Márquez, Redman, Rodriguez, & Roossinck, ; Ghabrial & Suzuki ; Figueiredo et al, ). These interactions may cause physiological and morphological changes in phytopathogens, leading to reduced pigmentation, asexual sporulation, loss of fertility and/or reduced growth rate, as well as reduction in virulence (Kanematsu, Sasaki, Onoue, Oikawa, & Ito, ; Rosseto et al, ; Van de Sande et al, ; Xie & Jiang, ).…”

Investigation of mycoviruses in endophytic and phytopathogenic strains of Colletotrichum from different hosts

“…These results suggested the presence of a novel twosegment dsRNA virus termed Colletotrichum acutatum partitivirus 1. Figueirêdo et al (2012) reported the detection of a mycovirus in a strain of Colletotrichum gloeosporioides causing anthracnose in cashew trees. TEM revealed the presence of isometric particles (30-35 nm in diameter), confirming that the infection of this C. gloeosporioides strain was by a mycovirus.…”

“…TEM was used as described by Figueirêdo et al (2012). Briefly, hyphae and spores of fungi grown in PDA medium were carefully removed with a glass slide, transferred to a mortar containing 0.2 mL 0.05 M cacodylate buffer, pH 7.2, and macerated with pestle.…”