Pathogenic Variability and Epidemiological Analysis of Phomapolyanthis in Tuberose

Abstract

Tuberose (Polianthes tuberosa L.) is an economically important ornamental crop widely cultivated in India for cut flowers, loose flowers, and essential oil production. In West Bengal, continuous cultivation under warm and humid conditions has favored the emergence of tip blight caused by Phoma polyanthis, a destructive foliar disease that reduces photosynthetic area, affects spike quality, and leads to significant yield loss. The present investigation was undertaken to study the epidemiology, pathogenic variability, and virulence diversity of P. polyanthis isolates collected from major tuberose-growing districts of West Bengal. Nine pathogen isolates were obtained from tip blight–infected leaves collected from different locations and purified under laboratory conditions. Pathogenicity and virulence were evaluated on the susceptible tuberose cultivar GKTC–4 through artificial inoculation. Disease development was monitored by recording mean diseased lesion length (MDLL) at 24-hour intervals up to 120 hours after inoculation. Disease progression dynamics were further analyzed by calculating lesion length increment (LDLI) between successive observations. Field data on percent disease index (PDI) associated with different cultivars and locations were also recorded to understand disease distribution. Significant variability in pathogenic behavior was observed among the isolates. At 120 hours after inoculation, lesion length ranged from 10.5 cm to 29.5 cm, indicating wide differences in aggressiveness. Based on lesion development, the Bankura and Nadia isolates were categorized as highly virulent; isolates from Howrah, South 24 Parganas, Burdwan, Purba Medinipur, and Hooghly were moderately virulent; while Birbhum and Coochbehar isolates were less virulent. Disease progression analysis revealed isolate-specific temporal patterns, with peak lesion expansion occurring at different growth intervals, suggesting differences in infection efficiency and colonization rate. Field observations showed considerable variation in disease incidence among cultivars, with the highest PDI recorded in GKTC–4 (78.31%) and comparatively lower incidence in Prajjal (20.00–23.11%), indicating differential host response under natural conditions. The study demonstrated substantial pathogenic and virulence variability among P. polyanthis populations across West Bengal. Understanding such variability is essential for accurate disease risk assessment, screening of resistant germplasm, and development of location-specific integrated disease management strategies. The findings provide baseline epidemiological information that will support future research on pathogen diversity, host–pathogen interactions, and sustainable management of tuberose tip blight.