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Occurrence and distribution of citrus leprosis virus (CiLV-C) in Honduras, Central America

Basal rot of Alstroemeria spp. caused by Fusarium oxysporum in Argentina

S.M. Wolcan1,2 *, H.E. Palmucci3 and P.J. Grego1

1 CIDEFI, Facultad de Ciencias Agrarias y Forestales, UNLP, 60 y 119, (1900) La Plata, Buenos Aires, Argentina
2 Comisión de Investigaciones Científicas de la Provincia de Buenos Aires, Argentina
3 Cátedra de Fitopatología, Facultad de Agronomía, FAUBA, Av. San Martín 4453, Buenos Aires, Argentina 

*swolcan@speedy.com.ar

Accepted for publication 08/11/06

Commercial varieties of Alstroemeria spp. (Alstroemeria, Peruvian Lily) were introduced to Argentina in the late 1990s with cropping concentrated in La Plata (Buenos Aires Province).  Since 2002, diseased plants have been found in several greenhouses (Fig. 1) and in an experimental soilless culture system.  Symptoms included yellowing progressing from the lower to upper leaves, hollow stems constricted at the base, and roots and rhizomes with brown rot (Figs 2 and 3).  Some affected floral stems remained shorter than healthy ones.

Figure 1: Alstroemeria plants naturally infected
with F. oxysporum in a crop		 Figure 2: Foliar chlorosis of alstroemeria caused by
F. oxysporum

Isolates of Fusarium sp. were consistently isolated on potato dextrose agar (PDA) from pieces of symptomatic stems, stored or uprooted rhizomes, and roots of different cultivars (following surface disinfection for 2 min in 2% NaOCl).  Isolates were identified as F. oxysporum on the basis of cultural and morphological characteristics (Booth, 1971; Nelson et al, 1983).  White to cream colonies developed on PDA, with purple pigmentation on the reverse side.  Macroconidia (3-5 septate), abundant single-celled microconidia borne in false heads on short monophialides; chlamydospores were observed.  Rhizoctonia solani was also isolated.

 
Figure 3: Rotted and healthy rhizomes of
alstroemeria		 Figure 4: Stems hollow and constricted
at the base (arrows)		  



Figure 5: Uninoculated (left) and inoculated plants (right) of alstroemeria in a pathogenicity test

Pathogenicity tests were done with two isolates each of F. oxysporum and R. solani from alstroemeria, by addition of rice kernels colonised with each isolate to potted soil, and by placing agar plugs of each isolate on stem-base wounds.  Six plants of cv. Alpine with 4 to 6 shoots were used per isolate and technique.  Plants in uninfested soil, with wounded but uninoculated stems, were used as controls.  Plants were incubated in a moist chamber for 48 h and then maintained at 22-28ºC.  Typical symptoms were observed on wounded stems inoculated with F. oxysporum after 15-18 days (Fig. 4) and after 20-25 days in stems from soil infested with F. oxysporum.  Uninoculated controls and plants inoculated with R. solani remained symptomless (Fig. 5).

Alstroemeria basal rot could be a serious problem in the future because it will be difficult to eliminate F. oxysporum from rhizomes, soil- and soil-less systems.  Chang & Mirza (1993) and Chang et al. (1994) cited F. oxysporum, R. solani and Pythium ultimum causing rhizome and root rots of Alstroemeria spp. in Canada.  More recently, fusarium wilt of alstroemeria has been reported from India (Shanmugam et al., 2006).  This is the first report of F. oxysporum causing basal rot of Alstroemeria spp. in Argentina.

Acknowledgements

These studies were funded by UBA (Ubacyt G076 Proyect) and CIC.

References

Booth C, 1971. The Genus Fusarium. Kew, Surrey, England: Commonwealth Mycological Institute.

Chang KF, Mirza M, 1993. The occurrence of root rot disease complex of alstroemeria in Alberta. Canadian Plant Disease Survey 73, 3–8.

Chang KF, Barr DJS, Hwang SF, Mirza M, 1994. Effect of interactions between Fusarium, Rhizoctonia, and Pythium on root and rhizome rot of Alstroemeria. Journal of Plant Diseases and Protection 101, 460–466.

Nelson PE, Tousson TA, Marasas WFO, 1983. Fusarium Species: An illustrated manual for identification. Pennsylvania, USA: Pennsylvania State University Press.

Shanmugam V, Kumar S, Singh MK, Verma R, Sharma V, Ajit NS, 2006. First report of alstroemeria wilt caused by Fusarium oxysporum in India. New Disease Reports 14, http://www.bspp.org.uk/ndr/jan2007/2006-79.asp

The British Society for Plant Pathology