Pathogenicity and morphological variabilities of Lasiodiplodia theobromae isolates in tuberose.
Peduncle blight, hitherto an unknown disease was found to be a major limiting factor to the cultivation of tuberose, as the disease incidence was noticed up to 42.60 per cent in pockets of Madurai district. Though Lasiodiplodia theobromae is an ubiquitous pathogen, its occurrence on tuberose is a new record. Peduncle blight disease infected tuberose plants were collected from seven places of Tamil Nadu, India. Among the seven isolates screened for virulence, isolate I1 collected from Agricultural College in Madurai district recorded maximum infection under artificial inoculation. The isolate I1 significantly recorded 570 mm lesion length in pinpricked buds and also recorded 47.00 mm mycelial growth per day. Lasiodiplodia theobromae produced dark brown, flask-shaped, ostiolate pycnidia, 110-170 mm × 60-130 mm in size appeared in seven-day-old cultures. Conidia were initially globose to oblong, hyaline and unicellular later turning brown and septate, measuring 18.5-21.7 mm × 8.0-11.2 mm. Compact, fluffy and sparse colony types were observed among the isolates. Significant variation was observed in morphological character and virulence among the Lasiodiplodia theobromae isolates.