Identification and characterization of Neopestalotiopsis clavispora associated with leaf blight of small cardamom (Elettaria cardamomum Maton)

Abstract

Leaf blight is a major foliar disease prevalent in all cardamom-cultivating tracts, manifesting in diverse forms of symptoms. In this study, six symptomatological variants were delineated based on the expression of foliar symptoms in cardamom genotypes (Malabar, Mysore and Vazhukka) and designated as SV 1 to SV 6. Among the symptomatological variants, SV 1, SV 2, SV 3 and SV 6 were more pronounced in Vazhukka, while SV 4 and SV 5 were prominent in Malabar type. Subsequent isolation from the variants yielded whitish colonies, which were correspondingly coded as SV 1 to SV 6. The conidia were fusiform, five-celled, with three median versicoloured cells, two terminal hyaline cells and measured 23.1–27.25 × 3.84–4.43 μm. The apical cells had two to three tubular, flexuous, unbranched appendages, whereas the basal appendage was single, tubular and unbranched. Based on conidial characteristics and molecular characterization with internal transcribed spacer rDNA region, partial β-tubulin, translation elongation factor 1 alpha and large subunit (28S) of the nrRNA genes revealed identity of the pathogens as Neopestalotiopsis clavispora. The pathogenicity test was performed on Malabar, Mysore and Vazhukka genotypes, and Koch’s postulates were proved. In-vitro interaction at three temperature regimes indicated that N. clavispora was inhibitory to Colletotrichum gloeosporioides at 10 and 30°C. Among the fungicides, carbendazim, propiconazole and carbendazim-mancozeb completely arrested hyphal growth of N. clavispora under in-vitro conditions. This study constitutes first report on the association of Neopestalotiopsis clavispora with leaf blight disease of small cardamom.