First Report of Ectophoma multirostrata Causing Root Rot in Chickpea

During a disease survey conducted in chickpea growing areas of central India in 2016 to 2017, the incidence of root rot in 300 fields was 25 to 30%. Infected plants showed foliar chlorosis, dry and brittle root system, and prominent black necrotic lesions on the taproot. One hundred fifty symptomatic root samples were used to isolate from the necrotic lesion on potato dextrose agar (PDA). Most of the fungal colonies obtained were identified as Macrophomina phaseolina (syn. Rhizoctonia bataticola), whereas isolations from a few samples (10 to 15%) recurrently yielded another fungus culturally similar to Ectophoma sp. The single hyphal tip method was employed to obtain a pure culture. After 7 days of incubation at 25 ± 2°C with a 12-h photoperiod, the culture was olive green to dark brown with appressed texture having small, predominantly globose pycnidial bodies (60.83 to 74.11 μm [SEM ± 1.67] in width and 97.56 to 112.66 μm [SEM ± 1.91] in length) embedded in the PDA. Numerous ellipsoid, hyaline, single-celled conidia varying from 7.83 to 8.30 μm (SEM ± 0.04, n = 30) in length and 3.44 to 3.85 μm (SEM ± 0.04) in width were released from the pycnidia. To determine pathogenicity, sterilized vertisol soil artificially infested with the above purified fungus was used. Infested soil was prepared by mixing 1 kg of soil with 50 g of inoculum grown in corn meal sand medium for 15 days (Pande et al. 2012). The seeds of chickpea cultivar BG 212 (locally grown cultivar from where the isolate was collected) were sown in the infested soil and watered regularly when required. Symptoms began as foliar chlorosis 21 days after sowing. As disease progressed, small black necrotic lesions on the roots were observed followed by rotting of the lateral and secondary root. The plants showed complete mortality after 30 days, and the infected plants could easily be uprooted. The fungus was successfully reisolated from the infected host tissue on PDA and reproduced similar colony characteristics as earlier morphology. The whole process was repeated thrice to confirm Koch’s postulates. The pathogen was tentatively identified as Ectophoma sp. based on the cultural characteristics and conidial morphology (Boerema et al. 2004). Further, molecular identification of the fungus based on the internal transcribed spacer region was conducted, wherein the PCR amplification of one representative isolate was carried out using ITS1 (forward) and ITS4 (reverse) primers. The amplicon product was sequenced, and a BLASTn search revealed 100% sequence similarity (524 bp nucleotide similarity) to Ectophoma multirostrata (syn. Phoma multirostrata) (Valenzuela-Lopez et al. 2018) isolate (accession no. KM659039) isolated from Coriandrum sativum in Australia (Golzar et al. 2015). The sequence was submitted to the GenBank database (accession no. MG897497). The pathogen E. multirostrata was previously reported from Fuchsia × hybrida, oregano, and Lavandula angustifolia. To the best of our knowledge, this is the first report of E. multirostrata causing root rot of chickpea.