MONIKA MISHRA, RANJANA BHATI* AND RAJ KUMAR MISHRA
Department of Microbiology, Bundelkhand University, Jhansi-284 128 (U. P.), India
*(e-mail: ranjana.iitkgp@gmail.com; Mobile: 9453039734)
(Received: August 2, 2025; Accepted: September 22, 2025)
ABSTRACT
Phytophthora stem blight (PSB), caused by Phytophthora drechsleri f. sp. cajani, is re-emerging as a serious soil-borne disease of pigeonpea (Cajanus cajan) in India. In the present investigation, 25 isolates of P. drechsleri were obtained from diseased pigeonpea plants and characterized for their cultural, morphological, physiological and pathogenic features. Considerable variability was observed in colony appearance, pigmentation and radial growth, leading to classification of isolates into fast, moderately fast, moderate, slow and very slow-growing groups. Sporangial morphology also differed markedly, with papillate, semi- papillate, non-papillate and chain-like forms documented. Pathogenicity tests under greenhouse conditions revealed significant variation in virulence: isolates P20 and P21 induced complete plant mortality, while others caused moderate to mild symptoms. Physiological studies indicated that optimal mycelial growth occurred at 26-30°C and pH 6.5-7.0, whereas growth was restricted under extreme acidic or alkaline
conditions. Overall, the study demonstrated substantial variability among P. drechsleri isolates in Bundelkhand and provided a basis for resistance breeding and the development of effective management strategies against PSB in pigeonpea.
Key words: Pigeonpea, Phytophthora stem blight, variability, pathogenicity