Phytophthora blight of Pigeonpea [Cajanus cajan (L.) Millsp.]: An updating review of biology, pathogenicity and disease management

Phytophthora blight (PB), caused by Phytophthora drechsleri f. sp. cajani, is reoccurring as an economically important disease of pigeonpea (Cajanus cajan), especially when excessive rains fall within a short span of time and hot and humid weather persists during the crop season. A few years after the initial reviews of Kannaiyan et al. (1984), the disease was coming to halt. Despite earlier investigations on pathological and physiological characteristics of P. drechsleri f. sp. cajani, the nature of infection process and genetic basis of pathogen variability have not been clearly established. Therefore, information on the biology and survival of the pathogen is needed to devise effective management strategies. Attempts have been made to develop green-house and field screening techniques since three decades ago for identification of host plant resistance. However, only few pigeonpea germplasm and breeding lines belonging to cultivated and wild Cajanus spp. were found tolerant to PB. The recent frequent recurrence of PB epidemics in the major pigeonpea growing areas prioritized the search for higher levels of disease resistance. There is a need to study the biology of the pathogen, epidemiology of the disease and refinement of the resistance screening techniques and develop integrated disease management technology for the disease. In this review, the symptomatology of the disease, biology of pathogen including its variability, epidemiology, sources of resistance, other management options and available information on biochemical and genetic basis of disease resistance have been updated and discussed with the identification of future research priorities.