Inheritance of downy mildew resistance and its relationship with biochemical traits in cauliflower (Brassica oleracea L. var. botrytis)

Downy mildew (DM) is a destructive disease of cauliflower and other Brassica vegetables that not only affects young seedlings and transplanted crop but also produces damaging abnormalities in the inflorescence of infected seed crops. The development of resistant cultivars is an alternative to control phytosanitary problems that affect cauliflower crop. This study was conducted to investigate the mode of inheritance of resistance to DM in cauliflower under field conditions and its association with biochemical traits. Six generations derived from hybridization between four diverse genotypes, namely DPCaY-3 (susceptible), Palam Uphar (susceptible), DPCaY-8 (resistant), and DPCaY-6 (resistant), were evaluated in the randomized block design along with standard check. The result of this study provided an indication that DM resistance was conditioned by a single dominant gene. In DPCaY-3 × DPCaY-8, DPCaY-3 × DPCaY-6, and PU × DPCaY-6, the segregation of F2 generations was in the ratio 3(R):1(S), which suggests the monogenic inheritance of resistance in these crosses. This was further confirmed by the test cross ratio of 1(R):1(S) in a backcross with the susceptible parent in all the three crosses. Correlation matrix revealed that plant disease (DM) index (PDI) exhibited significant and positive association with total sugars, whereas vitamin C and total phenols exhibited significant and negative relationship with PDI. This exemplifies the significance of these phytochemicals in plant-defense mechanism against pathogens.