**1. Introduction**

The crops in the *Brassicaceae* family are the most economically and nutritionally important for human consumption after cereals [1]. Based on utilities, Brassica species are broadly catego‐ rized into oilseed, vegetable, and sources of condiments. In the Brassica crops, canola/rapeseed is the second largest vegetable oil crop after soybean in the world [2]. Globally, rapeseed/canola has been cultivated in about 36.4 M ha with total production approximately 72.5 M tonnes [2]. Among the Brassica species, *B. napus*, *B. rapa*, *B. juncea*, and *B. carinata* provide about 15% of edible vegetable oil supplies around the world [3]. In addition, Brassica species such as *B. oleracea*, *B. rapa*, and *B. napus* supply nutritionally rich green leafy, stem and root vegetables for human daily diets. Brassica species also possess rich genetic diversity with respect to both speciation and the ample morphotypes [4], which designate important species to be investi‐ gated for genetic evaluation of plant kingdom. The Brassica crops, however, have significant impact by biotic stresses including diseases and pests, which challenge production and productivity of these crops.

Clubroot is one of the most threatening disease affecting global production and productivity of cruciferous crops including canola/rapeseed and Brassica vegetables. Clubroot disease is caused by the soil-borne obligate biotroph pathogen *P. brassicae* in Brassica crops. Cultivation of different Brassica oilseed and vegetable crops fulfills the host range requirement of the clubroot pathogen, which leads to wide spreading of the pathogen throughout the world. Since the emergence of the clubroot pathogen in vegetable crops of Brassica species, management of the disease has been a big challenge due to the obligate biotroph nature of the pathogen.
