Identification and Characterization of Sclerotinia sclerotiorum (Lib.) de Bary Associated with Rhynchosia bracteata Benth. Ex Bak. of Wild Derivatives of Pigeonpea from India

Abstract

Background: Pigeonpea [Cajanus cajan (L.) Millsp.], an important grain legume crop that is predominantly cultivated in tropical and sub-tropical regions of the world (Nene and Sheila, 1990). Crop wild relatives (CWR) are valuable source of novel alleles for economic traits which when transferred to cultivated species adapt well to changing biotic stresses, farming practices, market demands and climatic conditions. Under proposed study the detailed symptomatology, cultural, morphological and pathogenic characteristics of the causal agent and molecular identification of the pathogen were identified. Methods: Of the total 79 accession of wild relatives of pigeonpea (Cjanus cajan) planted in the experimental fields of ICAR- Indian Institute of Pulses Research (IIPR), Kanpur during 2017-18, one accession (ICP-817) of Rhynchosia bracteata was found to be affected by a disease characterized by leaf and stem blight symptoms. Disease symptoms appeared in January–February, 2017 and 2018. Presence of water soaked lesions on the leaves and stem which later turned chalky in appearance, cottony white mycelium on the affected plant parts along with black coloured irregularly circular sclerotia resembled those of white mold fungus Sclerotinia sclerotiorum (Lib) de Bary were observed. Result: Pathogenicity of the fungus was proved using detached leaf/twig inoculation techniques. Morphological characters and the sequences of internal transcribed spacer (ITS) region of the fungus confirmed the causal agent of the disease to be Sclerotinia sclerotiorum (Lib) de Bary. This is the first report of the Sclerotinia sclerotiorum on Rhynchosia bracteata not only in India but also in the world.