Differential biochemical response in resistant and susceptible barley (Hordeum vulgare) cultivars upon covered smut (Ustilago hordei) infection

Abstract

Covered smut of barley is an important seed borne disease caused by Ustilago hordei. This disease has been a serious threat and consequently necessitated understanding of barley-smut resistance mechanism. The present study focussed on the biochemical changes in three barley cultivars viz., PL426 (resistant), PL891 (moderately susceptible) and VJM201 (susceptible), during the infection process of covered smut. Dehulled seeds of each of these varieties were artificially inoculated with U. hordei (108 teliospore suspension) prior to germination and the seedling samples were collected at a day interval till 8 days after germination (DAG) for the study. The results revealed a significant increase in antioxidative activities of defense enzymes [peroxidase (POD), phenylalanine ammonia lyase (PAL), polyphenol oxidase (PPO)] and total phenolic content in inoculated samples than the uninoculated ones and the increase was more pronounced in resistant line (PL426) than susceptible (VJM201) and moderately susceptible (PL891) ones. PL426 recorded maximum activity of POD (86.70 units min−1 g−1 fw) and PPO (89.30 units min−1 g−1 fw) which leads to the accumulation of more phenols (0.64 mg/g). The biochemical results were further confirmed by observing the effect of aqueous extract of resistant and susceptible varieties on germination of teliospores of U. hordei. Maximum germination inhibition (98%) of teliospores was exhibited by PL426 when 100% concentration was used whereas the inhibition in case of PL891 and VJM201 was only 18% and 2%, respectively at the same concentration. The study has highlighted the changes in the most efficient antioxidative system that could limit the cellular damage caused by U. hordei.