A preliminary study on the genus Fusicladium s. l. in Iran

INTRODUCTION

FusicladiumBonord. was established to accommodate Venturia  Sacc. (Ascomycota, Pleosporales, Venturiaceae E. Müll. & Arx ex M. E. Barr) anamorphs with sympodial (denticulate) or percurrent (annellate) conidiogenous cells. Three genera were later distinguished based on the proliferation mode: Fusicladium with sympodial proliferation, Pollaccia E. Bald. & Cif. with monoblastic, determinate to percurrent conidiogenous cells (with few rather inconspicuous annellations) and Spilocaea Fr. with percurrent proliferation and numerous, conspicuous annellations. Braun et al. (2002) suggested that the separation of these anamorphic genera is not tenable since the conidiogenesis and structure of the conidiogenous loci are uniform. Molecular examinations clearly showed that Venturia is a monophyletic clade that can not be separated into sub-clades relevant to these anamorphic genera (Beck et al. 2005). Therefore, it is proposed that these genera to be merged in one anamorphic genus. Hence, the name Fusicladium was conserved against other names (Braun 2005). In this new concept, Fusicladium s. l. includes Fusicladium, Spilocaea, Pollaccia, Cycloconium and Pseudocladosporium (Braun et al. 2002, Braun 2005, Crous et al. 2007). They are phytopathologically relevant pathogens, causing leaf spot, necrosis, scab diseases as well as leaf and fruit deformations of at least 52 angiospermous plant genera. These fungi are host specific, mostly confined to a single host genus or allied host genera in a single family, e.g. Fusicladium pomi attacks members of Rosaceae (Schubert et al. 2003). A world monograph of the genus Fusicladium s. l. Bonord. em. Schubert, Ritschel et U. Braun was published in 2003 and 57 taxa belonging to the anamorphic genus were described (Schubert et al. 2003). Some genera such as Cladosporium are taxonomically related to Fusicladium. The structure of the conidiogenous loci and conidial hila proved to be the basic feature for a natural classification (David 1997), which could be confirmed by molecular examinations (Braun et al. 2003). True species of Cladosporium are characterized by having pigmented conidiophores with coronate conidiogenous loci, i.e. composed of a central convex dome surrounded by a raised periclinal rim, and pigmented conidia formed in acropetal chains (David 1997, Braun et al. 2003). Therefore, in a series of taxonomic studies of the genus Cladosporium s.l. several new species and new combinations are proposed in the genus Fusicladium (Schubert 2005, Schubert & Braun 2005a, b, Schubert & Braun 2007, Braun et. al. 2008, Crous et al. 2007, 2010a, b). Although several species of the genus Fusicladium including F. pomi, F. pyrorum, F. oleagineum,
F. eriobotryae, F. heterosporum, F. crataegi,
F. dendritichum (= F. pomi), F. virescens
(= F. pyrorum) and F. cerasiare so far reported from Iran (Hedjaroude & Abbasi 2000, Mahdian 2006, Ershad 2009, Askari & Ghaderi 2010, Sanei & Razavi 2011), but most of them are not adequately described based on Iranian materials. This paper presents a primary finding on the genus Fusicladium species and their hosts in Iran.

MATERIALS AND METHODS

Plant parts (twigs, leaves, fruits) showing Fusicladium spp. symptoms were collected from Guilan, Mazandaran, Qazvin and Ardabil provinces of Iran. Moreover, all Fusicladium specimens preserved at fungal collection of the University of Guilan were reexamined. VANOX AHBS3 Olympus light microscope was used to examine fungal structures, and a BH2 Olympus light microscope equipped with a SONY DSCHX1 digital camera was used for photography. Structures were mounted in lactic acid, and 30 and 10 measurements (× 1000 magnification) determined for conidia and conidiophores respectively, with the extremes of spore measurements given in parentheses. The identification of fungal species was determined according to Schubert et al. (2003). Host plants were identified according to Mozaffarian (1998). All collected specimens were deposited in the fungal collection of the Department of Plant Protection, College of Agriculture, University of Guilan, Iran.

RESULTS AND DISCUSSION

In our study, five species including F. carpophilum, F. fraxini, F. pomi, F. pyrorum and F. oleagineum were identified from newly collected plant materials in four provinces of Iran (Guilan, Qazvin, Ardabil and Mazandaran). F. carpophilum and F. fraxini are reported for the first time from Iran. Two species; F. cerasi and F. crataegi, which have already been reported from Iran (Schubert et al. 2003, Khabiri 1952, Esfandiari 1948a, Scharif & Ershad 1966) were not found in this study. A brief description of identified taxa and a key to Fusicladium species reported from Iran are presented.

Fusicladium carpophilum (Thüm.) Oudem., Verh. Kon. Ned. Akad. Wetensch., Afd. Natuurk.: 388 (1900) Fig. 1A, 2A

On fruits and twigs, patches on the fruits superficial, circular to oval, small, greenish brown, conidiophores solitary, erect, somewhat flexuous or straight, unbranched, 29–105 × 4–6.2 μm, septate, medium brown, smooth, sometimes swollen at the base, walls somewhat thickened. Conidiogenous cells integrated, terminal, 19–26 μm long, with 3–7 denticulate loci, 1–2 μm wide, unthickened, not darkened. Conidia catenate, cylindrical to fusiform, straight, 12.5–20(–22) × 4–5 μm, aseptate, pale olivaceous, smooth, hila truncate, 1–1.5(–2) μm wide, unthickened, somewhat darkened.

Specimens examined: IRAN, Tajan Gokeh village, Astaneh Ashrafieh, Guilan Province, on fruits of Prunus persica var. nectarine, 12 Jun. 2012, M. Mousakhah, (1029).

Fig. 1. Scab disease symptoms caused by Fusicladium s. l. species on leaves and fruits of few hosts in natural condition on: (A) Prunus persica var. nectarine, (B) Fraxinus sp., (C) and (D) Malus pumila, (E) Pyracantha coccinea, (F) Eriobotrya japonica, (G) Pyrus communis, (H) Khoj (local variety of Pyrus communis in Guilan Province, Iran), and (I) Olea europaea.

Fig. 2. Conidia and conidiophores of Fusicladium carpophilum (A) and F. fraxini (B). Scale bars = 10 μm.

Notes: According to Schubert et al. (2003) four species, F. pomi, F. obducens, F. cerasi and
F. carpophilum, have been reported on Prunus species. In F. obducens and F. cerasi the conidia often are not catenate. The latter three species have sympodial conidiogenesis. F. carpophilum differs from F. cerasi, a previously reported species from Iran, by having catenate conidia, longer conidiophores (25–100 μm) than those of F. cerasi [(10–)20–40(–60) μm] and its broad host range (rarely occurring on Prunus cerasus) compared with F. cerasi with narrow host range, mostly occurring on Prunus cerasus. Fusicladium carpophilum is a new record for the mycobiota of Iran.

Fusicladium fraxini Aderh.,Nova Hedwigia 36: 74, 83 (1897) Fig. 1B, 2B

Leaf spots amphigenous, circular to irregular, about 5 mm wide, olivaceous-brown on the upper leaf surface, conidiophores mostly erect, straight to geniculate, flexuous, often unbranched, sometimes branched, (18–)26–45(–50) ´ 4–7 μm, 0(–1) septate, pale olivaceous to medium brown, smooth, often conspicuously lobed at the base. Conidiogenous cells integrated, terminal or conidiophores usually reduced to conidiogenous cells, proliferation sympodial with 5–10(–14) loci, loci sub-denticulate, 1(–2) μm wide, minutely thickened. Conidia solitary, fusiform to obclavate, straight, (12–)14–17(–18) ´ (4–)5–6 μm, 1(–2)-septate, not or only slightly constricted at the septa, septa somewhat in the lower half, hila 1(–2) μm wide, unthickened.

Specimens examined: IRAN, College of Agricultural Science, University of Guilan, Rasht, on leaves of Fraxinus sp., 6 Jul. 2011, S. A. Hashemi, (1026), and IRAN, Ghalehroodkhan, Fuman, Guilan Province, on leaves of Fraxinus sp., 4 Aug. 2005, S. A. Khodaparast, (1025).

Notes: So far two species have been described on Fraxinus; Fusicladium fraxini and F. nebulosum that can be separated in conidiophore size, proliferation, colour, etc. (Schubert et al. 2003). F. fraxini is a new record for mycobiota of Iran. Conidiophores of Iranian isolates of F. fraxini are conspicuously lobed at the base. This character was not mentioned in Schubert et al. (2003). Further studies on these isolates are in progress to evaluate this character value in terms of taxonomy.

Fusicladium pomi (Fr.) Lind, Danish fungi: 521 (1913) Fig. 1C-F, 3A-C

On living leaves and fruits, spots amphigenous, sub-circular to irregular, up to 10 mm wide, pale olivaceous-brown, becoming greyish black, on leaves sometimes surrounded by a yellowish halo, often around the main midrib, occasionally covering large leaf segments. On fruits forming small, circular to irregular spots, sub-cuticular, margin indefinite, olivaceous-brown. Conidiophores mostly in loose to dense fascicles, erumpent through the cuticle, erect, straight to slightly flexuous, cylindrical to ampulliform, unbranched, 14–22 ´ 7–10 μm, aseptate (on yellow apple), 19–31 × 7 μm, aseptate (on red apple), 10–25 ´ 5–7 μm, aseptate (on Eriobotrya japonica) and (14–)24–58 ´ 5–6 μm, (0–)1 septate (on Pyracantha sp.), walls thickened, often swollen at the base. Conidiogenous cells integrated, terminal, with a single locus, proliferation percurrent, with conspicuous annellations, loci truncate, 4–5μm wide, unthickened, not darkened. Conidia solitary, shape variable, ovoid to obpyriform or obclavate, straight, (12–)16–25 (–26) × 7–9 μm, 0(–1) septate (on yellow apple), (13–)17–24 (–26) × 7 μm, 0(–1) septate (on red apple), (11–)13–18´ 7–9 μm, aseptate (on Eriobotrya japonica) and 12–18 ´ 7–10 μm, 0(–1) septate (on Pyracantha sp.), walls somewhat thickened, narrowly pointed or broadly rounded at the apex, truncate at the base. Hilum (3–)4–5(–6) μm (on yellow apple), (3.5–)4–5(–6) μm (on red apple), 4–5(–6) μm (on Eriobotrya japonica) and 2.5–5 μm (on Pyracantha sp.) wide, truncate, unthickened to occasionally very slightly thickened, not darkened.

Fig. 3. Conidia and conidiophores of Fusicladium pomi on Malus pumila (A), on Pyracantha sp. (B) and on Eriobotrya japonica (C), F. pyrorum (D) and F. oleagineum (E). Scale bars = 10 μm.