versión On-line ISSN 1851-5657
Phyton (B. Aires) v.76 Vicente López ene./dic. 2007
Cylindrocladium spathiphylli, a causal agent of root and crown rot of Spathiphyllum wallisii in Buenos Aires, Argentina (With 5 Figures)
Cylindrocladium spathiphylli, agente causal de la podredumbre de raíz y corona de Spathiphyllum wallisii, en Buenos Aires, Argentina (Con 5 figuras)
Grijalba PE, HE Palmucci
Cátedra de Fitopatología. Facultad de Agronomía de la Universidad de Buenos Aires (FAUBA). Av. San Martín 4453. (1416) Buenos Aires. Argentina. Address Correspondence to PE Grijalba; e-mail: email@example.com
Recibido/Received 18.07.2007. Aceptado/Accepted 19.08.2007.
Abstract. A new disease of Spathiphyllum wallisii plants, characterized by leaf yellowing and wilting due to root and crown rot, was observed in nurseries of the Great Buenos Aires, Argentina. A fungus was consistently isolated from diseased tissue and identified as Cylindrocladium spathiphylli, on the base of its morphological and cultural characteristics. Inoculation tests were carried out which confirmed this fungus as the causal agent of the disease. This is the first report of C. spathiphylli causing root and crown rot of S. wallisii in Buenos Aires.
Key words: Spathiphyllum wallisii; Cylindrocladium spathiphylli; Root and crown rot.
Resumen. Una nueva enfermedad de espatifilo ( Spathiphyllum wallisii ) apareció en viveros del Gran Buenos Aires, Argentina. Esta se caracteriza por síntomas de amarillamiento y marchitamiento foliar debido a la podredumbre del cuello y descortezamiento de raíces. Un hongo aislado del tejido afectado fue identificado como Cylindrocladium spathiphylli, sobre la base de sus características culturales y morfológicas. Las pruebas de inoculación llevadas a cabo con el hongo aislado confirmaron que éste es el agente causal de la enfermedad. Este es el primer registro sobre la presencia de este patógeno afectando a plantas de S. wallisii en Buenos Aires.
Palabras clave: Spathiphyllum wallisii; Cylindrocladium spathiphylli; Podredumbre de raíz y corona.
Spathiphyllum wallisii Regel (Araceae) is a popular pot plant, native to South America (Parodi & Dimitri, 1978). A new disease appeared in the Great Buenos Aires which severely limits Spathiphyllum production. Diseased plants, received in June 2005 from local nurseries, showed yellowing of lower leaves and wilting due to a root rot, which later killed most of the diseased plants (Fig. 1a). Such plants could be easily removed from the pots because of the destruction of the root system. A few elliptical brown spots could be observed on leaves (Fig. 1b). Routine phytopatological tests were performed to determine the causal agent of this disease.
Small pieces (3-4 mm diameter) of diseased leaf, crown and root tissue were surface disinfected by immersion in a solution of 2% sodium hypochlorite for 2 min and then rinsed several times in sterile distilled water. They were then placed on 2% potato dextrose agar (PDA), acidified to pH 6.5, in Petri dishes which were incubated in the dark at 22 ± 2 ºC for 48 h. Later on, they were subjected to a 12 h photoperiod (near ultraviolet light- Philips tubes TL 40/08), at the same temperature.
The same fungus was consistently isolated from the diseased plant tissues. After 48 h of incubation, fungal growth was observed forming a white cottony mycelium, which later turned red-brown and produced a dark reddish brown pigmentation after one week (Fig. 2). Microscopic observations revealed septate hyphae and hyaline conidiophores which branched dichotomously, with two to four cylindrical phialides. Sterile filaments ended in a globose hyaline vesicle typical of the genus Cylindrocladium (Fig. 3). Cylindrical, straight, hyaline conidia of 62 (45.5 -78.7) x 6 (4.7- 7.2) µm, rounded at both extremes and usually having one-septate, were formed singly at the phialide tips (Figs. 4, 5). Reddish brown chlamydospores occurred in clusters and formed soft microsclerotia in culture media. Based on these morphological and micrometric characteristics, the fungus was identified as Cylindrocladium spathiphylli Schoulties, El-Gholl & Alfieri (Schoulties et al., 1982). The corresponding teleomorph ( Calonectria spathiphylli El-Gholl, Uchida, Alfenas, Schub, Alfieri & Chase) was not observed. The isolate was deposited in the culture collection of the Facultad de Agronomía, Buenos Aires, Argentina.
Stem bases and roots of five healthy Spathiphyllum plants were inoculated with a spore suspension obtained from a 10-day-old culture grown on PDA and adjusted to 104 conidia/ml. Inoculated plants were covered with plastic bags to maintain high relative humidity and placed in a growth chamber at 22 ºC ± 2 ºC during 10 days; thereafter, they were kept in the greenhouse. Control plants were inoculated only with sterile, distilled water. After 15 days, the inoculated plants showed similar symptoms as the spontaneously diseased plants. Control plants remained without symptoms. Koch's postulates were fulfilled by reisolating the same fungus from the inoculated plants. It was concluded that C. spathiphylli is the causal agent of root and crown rot of S. wallisii.
A Cylindrocladium,isolated from diseased plants of Spathiphyllum sp., was originally identified as C. floridanum (Schoulties & El-Gholl, 1980), but later Schoulties et al. (1982) described it as a new species, C. spathiphylli. Recently, C. spathiphylli was found in the Federal District, Brazil (Reis et al., 2004). Colombo et al. (2005) have reported the presence of C. spathiphylli in a nursery in Corrientes (Argentina), but no morphological or pathogenicity studies were carried out. Thus, the present is the first description of C. spathiphylli in Argentina and the first report of this fungus causing disease on S. wallisii in Buenos Aires.
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