First report of alstroemeria wilt caused by Fusarium oxysporum in India

Abstract

Hybrids of Alstroemeria spp. (Alstroemeriaceae), commonly called Peruvian Lily, are an exotic, rhizomatous and perennial cut flower crop widely cultivated under protection in India. Nine hybrids (cvs Alladin, Amor, Capri, Cinderella, Pluto, Rosita, Serena, Tiara and No. 14) were procured from three locations in India by the Institute of Himalayan Bioresource Technology (IHBT) in 2000–2001. During cultivation, plants of all cultivars exhibited leaf chlorosis and slight vein clearing on outer leaflets, followed by leaf yellowing and abscission, discolouration of stem vascular tissue and death. Fusarium oxysporum was consistently isolated when sections of discoloured stem vascular tissue were surface sterilised (2% sodium hypochlorite) and incubated on potato dextrose agar or carnation leaf agar. Single-spore isolates were identified based on morphological characters (Nelson et al., 1983). Conidiophores were unbranched or branched short monophialides. Microconidia were abundant, generally single celled, oval to kidney shaped and produced only in false heads 5–12 × 3–3·5 μ m. Macroconidia were abundant, slightly sickle-shaped and thin-walled, with an attenuated apical cell and a foot-shaped basal cell 35·0–60·0×3·0–5·0 μ m. Chlamydospores were single or in pairs and profusely distributed. Thepresence of chlamydospores and microconidia borne in false heads on short monophialides distinguished the fungus from closely related Fusarium species. The culture has been deposited in the Microbial Type Culture Collection (MTCC 7677) of the Institute of Microbial Technology, Chandigarh, India. The identity of the culture was also established by PCR amplification and sequencing of the internal transcribed spacer (ITS) region (White et al ., 1990) (GenBank Acc. No. AM 261761). Pathogenicity tests were done twice in a screen house on 8-week-old plants of cv. No. 14. Wounded roots were submerged for 10 min in a conidial suspension (1 ×10 6 conidia per mL in sterile tap water), while control plants were dipped in sterile tap water. Seedlings were transplanted into pots and maintained in a polytunnel. Symptoms observed on inoculated plants were similar to those in commercial glasshouses, including leaf wilt (3 weeks after inoculation), chlorosis, necrosis and plant death. The pathogen was re-isolated from the stems of affected inoculated plants to confirm Koch’s postulates. The control plants did not exhibit symptoms. Root rot complex of alstroemeria caused by F. oxysporum in association with Pythium irregulare and Rhizoctonia solani was earlier reported in Canada (Chang & Mirza, 1993) and Germany (Chang et al ., 1994). This is the first report of Fusarium oxysporum causing alstroemeria wilt in India.