Association between enzyme activity levels in Eucalyptus clones and their susceptibility to the gall wasp, Leptocybeinvasa, in South China

Abstract

The activity levels of five defensive enzymes, namely, peroxidase (POD), polyphenol oxidase (PPO), superoxide dismutase (SOD), phenylalanine ammonia-lyase (PAL) and catalase (CAT) were assessed in shoots of four commercial Eucalyptus clones (DH201-2, DH32-29, U6, GL9) at ages of 13, 29 and 38 months. Levels were also assessed in healthy and damaged shoots of clone DH201-2 at 15 months, shortly after it was severely attacked by the shoot gall wasp Leptocybe invasa. Foliar levels of these five enzymes did not show any significant increase with age. The level of CAT was found to be significantly higher at ages 29 and 38 months in clone GL9, a clone relatively resistant to L. invasa, than in the three other clones. Clone DH201-2, which was relatively susceptible to L. invasa, had non-significantly lower CAT levels than the rest of the clones at all three ages examined. The levels of the other four enzymes showed no obvious differences between clones and overall activity levels of the five enzymes did not show any clear association with the qualitative ranking susceptibility of the clones to L. invasa. In 15-month-old DH201-2 trees, marked increases in the levels of CAT, SOD and PPO were observed in shoots attacked by L. invasa compared with shoots from healthy trees of the same age, while levels of PAL and POD decreased compared with those in shoots from healthy trees.

Aras aktiviti lima enzim pertahanan iaitu peroksidase (POD), polifenol oksidase (PPO), superoksida dismutase (SOD), fenilalanin ammonia-liase (PAL) and katalase (CAT) dinilai dalam pucuk empat klon Eucalyptus komersial (DH201-2, DH32-29, U6, GL9) yang berusia 13 bulan, 29 bulan dan 38 bulan. Aras enzim turut dinilai dalam pucuk yang sihat serta yang rosak bagi klon DH201-2 yang berusia 15 bulan tidak lama selepas ia diserang penyengat puru, Leptocybe invasa. Aras kelima-lima enzim daun tidak menunjukkan peningkatan signifikan dengan usia. Aras CAT lebih tinggi pada klon GL9 yang berusia 29 and 38 bulan. Klon GL9 secara relatifnya lebih rintang terhadap L. invasa berbanding ketiga-tiga klon yang lain. Klon DH201-2 yang agak rentan terhadap L. invasa mempunyai kandungan CAT yang lebih rendah berbanding klon lain yang dikaji. Aras enzim empat lagi enzim tidak menunjukkan perbezaan ketara antara klon. Secara keseluruhannya, aras aktiviti kelima-lima enzim tidak menunjukkan sebarang hubungan yang jelas antara tahap kerentanan kualitatif klon terhadap L. invasa. Pokok DH201-2 yang berusia 15 bulan menunjukkan peningkatan ketara dalam aras CAT, SOD dan PPO bagi pucuk yang diserang L. invasa berbanding pucuk pokok sihat yang sama usianya. Aras PAL and POD pula menurun berbanding pucuk pokok sihat.