Status of Defensive Enzymes and Contents of Total Phenols, Tannins and Nutrients Determine Aphid Resistance in Barley

Abstract

The present investigation was carried out to identify the biochemical traits responsible for aphid resistance in barley (Hordeum vulgare L). The genotypes showing differential response towards aphid attack, i.e. EC-492253, EC-492255, EC-492350, BCU-423 and PL-426 were taken for the present study. The grain yield was found to be maximum in EC-492253 and BCU-423, moderate in EC-492255 and EC-492350 while minimum in PL-426 genotype under natural aphid attack. The activities of defensive enzymes viz. polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL), β-1, 3-glucanase and chitinase were determined in the flag leaves and grains of all the genotypes during different stages of development. The various biochemical constituents, i.e. total phenols, total soluble proteins, free amino acids, sugars and tannins were also estimated. The higher activities of PAL, PPO, β-1, 3-glucanase and chitinase along with the higher contents of total phenols and tannins in the flag leaves and grains of tolerant genotypes might attribute towards pest resistance. On the other hand, the higher contents of total soluble proteins, free amino acids and sugars in the flag leaves of susceptible genotype could be responsible for making it a better host for the aphids. The results of the multivariate principal component analysis showed that the susceptible, moderately tolerant and highly tolerant genotypes occupied distinct positions on the graph on the basis of enzymatic activities and biochemical constituents. It was further observed that there was a fine relation between the biochemical traits identified for stress tolerance and the grain yield of these genotypes.