First Report of Neoscytalidium dimidiatum Causing Stem Canker of Dragon fruit ( Hylocereus spp .) in India

Dragon fruit ( .) is a tropical perennial plant (Family Cactaceae) that is popular for consumption in India. Originated from Central and South America and currently became popular in India. and are the most commonly cultivated species in India. During August to December, 2021, stem cankers were observed in commercial orchards within the Satara, Pune and Solapur districts of Maharashtra. The disease incidence across four orchards was approx. 40% and severity ranged between 30 and 80%. Initial symptoms on infected cladodes were minute, circular, depressed chlorotic spots often with a brick red flecks followed by elevation of the centre of the lesion. Later the lesions turned necrotic and contained black, erumpent pycnidia, followed by chlorosis and stem rot. Twelve diseased cladodes from different orchards were collected and isolations were conducted. Edges of the lesions (5 to10 mm ) were excised and surface sterilized by exposure to 1% sodium hypochlorite (2 min) followed by triple rinsing with sterilized distilled water. Excess moisture was removed with sterilized blotter paper and pieces were plated on potato dextrose agar (PDA) amended with streptomycin sulphate (30 mg/L) for 3 days at 27 ± 2°C with a 12 h photoperiod. All twelve isolation attempts yielded uniform fungal colonies and out of these, purified colonies from each location viz., SLNeo, LNeo, MGNeo and KNeo were selected for etiology study. On PDA, initially white mycelial colonies turned to olive green to grayish with dark gray to black pigmentation. Colony growth was rapid (30 mm/day). Brown, branched septate hyphae fragmented to produce abundant arthroconidia in chains that were hyaline to dark brown, thick walled, 0 to 1 septate, ellipsoid to ovoid (10.1 ± 1.4 × 4.88 ± 1.1 μm), rod (9.0 ± 0.8 μm × 5.3 ± 0.8 μm), round (7.9 ± 1.6 μm) and capsule (14.2 ± 3.1 × 6.1 ± 0.8 μm) shape. Conidia from pycnidia developed on host tissues were aseptate, hyaline and ellipsoid-cylindrical (8.2 ± 0.8 × 2.2 ± 0.3 μm) in shape. Based on morphological characteristics, the isolates were identified as (Penz.) Crous & Slippers (Crous et al. 2006). Molecular characterization was done by amplifying the partial internal transcribed spacer (ITS) region, and translation elongation factor 1-α and β-tubulin genes of four isolates using ITS1/ITS4, EF1-728F/EF1-986R and BT2A/BT2B primers (White et al. 1990, Glass and Donaldson 1995, Carbone and Kohn 1999). Sequences were deposited in GenBank accesions (ITS: OM884028, OM