Helminthosporiosis Impact on the Photosynthetic Apparatus and the Oxydative Status of Barley Seedlings at Different Stages of Development

In recent years, spot blotch, a disease caused by Bipolaris sorokiniana (Sacc.) Shoem., has emerged as a serious concern with regard to spring barley cultivation. However, the effect of this pathogen on the photosynthetic apparatus and oxidative status of barley plants at different stages of chloroplast development has hardly been studied.

The study aimed to evaluate the photosynthetic apparatus and protective system of a spring barley’s (Hordeum vulgare L.) response to Bipolaris sorokiniana (Sacc.) Shoem. (B.S.) at different stages of chloroplast biogenesis. The green seedlings of different ages (3-11 days) were treated with fungal spores (10⁶ spores×ml^−l). The first leaves of seedlings were analyzed 24 or 48 hours after the inoculation with the pathogen.

Differences in response to fungal infection were identified in leaf tissues containing chloroplasts at different stages of development. The differences manifested themselves in the non-photochemical quenching (NPQ) of absorbed energy, the total content of reactive oxygen species (ROS), lipid peroxidation (LPO) activity and polyphenol content. An increase in peroxidase (POX) activity in infected barley seedlings at the anabolic stage of chloroplast biogenesis and its decrease at the catabolic stage against the background of a constant increase in ascorbate peroxidase (APX) activity were revealed. A high positive correlation between the chlorophyll and malondialdehyde content (MDA) was observed.

In barley seedlings of different ages, a response to fungal contamination is different in the PS II activity, the general content of ROS and polyphenols, as well as the LPO activity. The photosynthetic and oxidative parameters of barley plants may be a useful tool to control plant immunity in view of breeding and novel protective technologies.