Molecular characterisation of Fusarium oxysporum causing rot diseases in small cardamom ( Elettaria cardamomum Maton).

Incidence of root rot and foliar yellowing, rhizome rot, panicle wilt and stem rot diseases of small cardamom (Elettaria cardamomumMaton) are caused byFusarium oxysporumSchlecht., and were surveyed in the high ranges of Idukki district, Kerala during 2010–2011. The diseases were noticed in different areas to varying degrees. Root rot was found to be most severe, followed by pseudostem rot, rhizome rot and panicle wilt. TheFusariuminfections were prevalent throughout the year (January–December) and varied from 1.5 to 10.6%. Even though the pathogen was isolated from different plant parts, during pathogenicity studies, all the isolates could cross-infect other plant parts too. Twenty different isolates ofF. oxysporumwere obtained from diseased samples, and five morphologically distinct isolates were analysed with Randomly Amplified Polymorphic DNA (RAPD) markers to study the genetic variability, if any, among them. PCR amplification of total genomic DNA with random oligonucleotide primers generated unique banding patterns, depending upon primers and isolates. Nine oligunucleotide primers were selected for the RAPD assays, which resulted in 221 bands for the five isolates ofF. oxysporum. The number of bands obtained was entered into an NTSYS, and the results showed moderate genetic variability amongF. oxysporumisolates causing root rot, rhizome rot, panicle wilt and pseudostem rot, collected from different locations. The dendrogram of different isolates into groups resulted in one major cluster at 0.61 similarity index comprising of four isolates (CRT 3, CRR 3, CPW 2 and CSR 1) and one isolate (CRT 5) formed in a separate cluster. Among the five isolates ofF. oxysporum, CRT 5 was entirely different from the other four isolates. The isolates also differ according to the geographical area, as revealed from the genetic variability observed in different root rot isolates (CRT 3 and CRT 5). It is inferred that despite moderate variability,F. oxysporum, infecting small cardamom in Idukki district of Kerala, consists of a single clonal lineage. [ABSTRACT FROM PUBLISHER]