Expression Profiles of Defense-Related Genes in Response to Aphid Inoculation in Different Chrysanthemum Cultivars

The expression profiles of genes involved in the defense enzyme system, lignin biosynthesis and flavonoids pathway encoding peroxidase (POD), polyphenoloxidase (PPO), phenylalanine ammonia lyase (PAL), catechol-o-methyltransferase (COMT), ferulate 5-hydroxylase (F5H), chalcone synthase (CHS) and dihydroflavonol reductase (DFR) were determined using real-time quantitative PCR in chrysanthemum cultivars differing in aphid resistance. The results indicated that POD, PPO, PAL, COMT and F5H were induced in highly aphid resistant 'Keiun', moderately resistant 'Han6' and susceptible 'Jinba', whereas CHS and DFR were induced only in two aphid resistant cultivars, but not in susceptible 'Jinba'. The transcripts of POD, PPO, PAL, COMT and F5H genes increased more rapidly and peaked earlier in the resistant 'Keiun' and 'Han6' than in the susceptible 'Jinba'. The different expression profiles of these genes in response to aphid inoculation between resistant and susceptible cultivars suggested that these genes probably play important roles in aphid resistance of chrysanthemum.