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CYP83B1, a CytochromeP450 member, a branch point enzyme connects metabolic flux of two important pathways Auxin and Glucosinolates biosynthesis. Necrotrophic fungi induce damage in the host and causes inability to down-regulate the auxin pathway thus increasing the plant susceptibility to pathogen attack. Significant reduction in radial growth pattern and sporulation count was seen >500 ppm auxin concentration in two isolates of <i>Alternaria brassicae</i> (CaAbD2) and <i>Alternaria brassicicola</i> (CaAbcR6) with respect to control. Expression profiling of CYP83B1 was performed using semi-quantitative RT-PCR of both isolates grown on supplemented media with IAA ranging from100 ppm-900 ppm. There was a marked increase in CYP83B1 expression at in <i>Alternaria brassicae</i> till 900 ppm. On the other hand decrease in expression was observed from 100 ppm to 800 ppm with a significant up regulation at 900 ppm of IAA concentration in <i>A. brassicicola</i>. As per biochemical estimation (HPLC) of IAA in infected two months old cauliflower leaves (Ab and Acola), a decreased trend of IAA was observed twenty days after infection compared to healthy leaf, indicating abiotic stress on the infected leaves. Varied gene expression of CYP83B1 was observed by quantitative Real time RT-PCR. <p><p>Keywords: Plant Stress-Abiotic Disorder, Vegetables, Brassicas (Crucifers)