Phylloxera infestation and the uptake and distribution of 13C and 15N 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 13C photosynthates and 15N in the grape vine 'Wuhe 8612' in response to phylloxera infestation were investigated. Phylloxera and grapevines cocultivated in pots were treated with 13CO2 and 15N-urea. The plant weight, nitrogen concentration and accumulation, 15N utilization efficiency, Nitrogen derived from fertilizer (Ndff%), and carbon isotope ratio (δ13C) 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 15N utilization efficiency, by 24 % and 14 %, respectively compared to controls. Labeled leaves of infested plants took up rather more 13C and 15N and exported a substantial amount of these nutrients to roots. Labeled roots took up rather more 15N and exported a small amount of these nutrients to upper leaves. This study found that phylloxera infestation reduced 13C and 15N 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.