Journal of Plant Pathology Archive

Abstract:

In 2014 and 2015, cucumber (Cucumis sativus L.) seedlings in polyhouses of IARI initially exhibited water-soaked lesions on roots that turned reddish brown to get decayed. Leaves displayed yellowing and the plants exhibited wilting resulting in poor stands. A fungus isolated from infected tissues on potato dextrose agar displayed dense and white aerial mycelium, with orange sporodochia on old cultures. Microconidia were lemon to pear shaped with 0-1 septum. Macroconidia were sickle shaped with their basal cells distinctly foot shaped or notched. Based on these characters, the fungus was identified as Fusarium solani Mart. Sacc. (Nelson et al., 1983). The identity of the culture was also established by sequencing the internal transcribed spacer (ITS) region (GenBank Accession No. KU883629). The fungus exhibited 98% similarity with a F. solani isolate of guava causing vascular wilt (HQ265420.1). Pathogenicity tests were done twice in a screen house on 3-week-old plants of cv. Pusa Uday. Wounded healthy roots were submerged for 10 min in a conidial suspension (1×106 conidia per ml in sterile tap water), while control plants were dipped in sterile tap water. Seedlings were transplanted into pots containing sterile soil. Symptoms observed after 3 weeks on inoculated plants were similar to those in commercial polyhouses. The pathogen was re-isolated from the infected tissues to confirm Koch’s postulates. The control plants did not exhibit symptoms. F. solani inciting vascular wilt in cucurbitaceous crops is reported elsewhere (Mehl and Epstein, 2007). This is the first report of F. solani infecting cucumber from India.