Arbuscular mycorrhizal fungi (AMF) induced hardening of micropropagated pomegranate (Punica granatum L.) plantlets

Improper hardening leads to high field mortality and poor growth of in vitro raised plantlets which poses a major hurdle in utilization of in vitro propagation for pomegranate. In this study four arbuscular mycorrhizal fungi (AMF) strains namely, Glomus mosseae, Acaulospora laevis, Glomus manihotis and a mixed AMF strain were used as biohardening agents to improve survival and growth of in vitro raised pomegranate plantlets. Plantlets inoculated with G. mosseae gave highest survival (90.40% and 88.00% at 60 and 90 DAI, respectively) and root colonization per cent (47.40 and 87.60 at 60 and 90 DAI, respectively). The predominant effect of G. mosseae was also evident on increased plant height (24.96 and 30.50 cm at 60 and 90 DAI, respectively) and root length (23.42 and 27.68 cm at 60 and 90 DAI, respectively) of the inoculated plantlets. G. mosseae and G. manihotis were found more effective in improving most of the growth, physiological and biochemical attributes of inoculated tissue culture raised plantlets. However, total phenol (24.94 and 28.62 μg/g at 60 and 90 DAI, respectively) and total chlorophyll (3.70 and 3.96 mg/g at 60 and 90 DAI, respectively) were found highest in mixed AMF inoculated plantlets.

► Bio-hardening of in vitro raised plantlets is mandatory for effective commercialization of tissue culture technique in pomegranate.
► Identified suitable AMF strains for bio-hardening of micropropagated pomegranate plantlets.
► Growth, physiological and bio-chemical activities were effectively improved by bio-hardening.