Effects of nodding broomrape parasitism on growth, physio-biochemical changes and yield loss of Withania somnifera (Linn.) Dunal plant

Ashwagandha ( Withania somnifera Dunal. Linn.) also known as Indian ginseng is the most widely used herb to boost the immune system. The main economic part of this plant is its roots and the principal active ingredients in roots are a group of steroidal lactones; collectively known as withanolides. Achlorophyllous holoparasitic angiosperm nodding broomrape ( Orobanche cernua Loefl.) is a root parasite living on a range of host plant species. To our best knowledge, there have been no reports on the effects of nodding broomrape parasitism on the growth, behaviour, and quality of W. somnifera plants. Physiological and biochemical parameters of broomrape-infected plants were studied and compared with those of uninfected plants. At 120 days after sowing (DAS) the net photosynthetic rate ( P N ) and stomatal conductance ( g S) in infected plants were 68% and 69%, respectively of those of the uninfected plants. The leaf nitrate reductase activity in infected plants was 88% and 48% of uninfected plants at 100 and 120 DAS, respectively. Chemo-profiles showing the absence of withanolide in broomrape stems demonstrated that this parasite does not mine withanolide from the host plant. Broomrape infestation had resulted in overall stunted growth causing an 83% decline in leaf area, reduced total biomass by 82%, decreased root yield by 68%, and major withanolide yield by 38% at 145 days after sowing. Future research on the management of broomrape in W. somnifera is suggested to prevent a huge yield loss in this important medicinal root crop.