Phylloxera infestation and the uptake and distribution of 13 C and 15 N tracers in grape vines

In order to study the reason phylloxera ( Daktulosphaira vitifolia Fitch) feeding on roots leads to decreased plant productivity, the uptake and distribution of  13 C photosynthates and  15 N in the grape vine 'Wuhe 8612' in response to phylloxera infestation were investigated. Phylloxera and grapevines cocultivated in pots were treated with  13 CO 2 and 15N-urea. The plant weight, nitrogen concentration and accumulation,  15 N utilization efficiency, Nitrogen derived from fertilizer (Ndff%), and carbon isotope ratio (δ 13 C) of different organs were measured. Phylloxera infestation significantly reduced grape weight, shoot length, and N concentration and accumulation in different organs, whereas it increased the ratio between N content of the of roots and above-ground organs. Phylloxera infestation reduced leaf and root nitrogen  15 N utilization efficiency, by 24 % and 14 %, respectively compared to controls. Labeled leaves of infested plants took up rather more  13 C and  15 N and exported a substantial amount of these nutrients to roots. Labeled roots took up rather more  15 N and exported a small amount of these nutrients to upper leaves. This study found that phylloxera infestation reduced  13 C and  15 N uptake in leaves and roots, but increased N and photosynthates, which were mostly distributed to the roots, but also to the upper leaves. These factors together led to weak grape vine growth.