ALTERATIONS IN THE LEVELS OF PHENOLICS AND PEROXIDASE-ACTIVITIES INDUCED BY RHOPALOSIPHUM-PADI (L) IN 2 WINTER-WHEAT CULTIVARS

Seedlings of two winter wheat cultivars differing in their resistance to cereal aphids, partly resistant Regina and susceptible Zdar, were e xamined for the content of free, soluble ester-, glycoside- and insolu ble cell wall-bound phenolic acids (PhAs) and peroxidase activity. Pla nts were cultivated in growth chambers and at the second leaf stage we re infected by apterous females of bird cherry-oat aphid, Rhopalosiphu m padi. After 10 days infestation the numbers and dry mass production of R. padi were significantly higher in Zdar than in Regina. A certain degree of resistance to aphids in unifested seedlings of Regina was a ssociated with higher level of free PhAs, higher content of methoxyphe nolic acids e.g. vanillic, ferulic and sinapic acids, and higher perox idase activity (related to susceptible Zdar), the increase in cell wal l-bound PhAs (in both cultivars), the accumulation of salicylic and sy ringic acids (more pronounced in Regina), the double increase in the a mount of sinapic acid (determined only in Regina) and the increase in peroxidase activity in both cultivars (higher in Zdar). The active res ponse to feeding of R. padi and the unspecific, general response to bi otic stress in seedlings of tested cultivars after R. padi infestation are discussed.