Variations in the galling reaction of grapevines: Evidence of different phylloxera biotypes and clonal reaction to phylloxera

The level of galling of five rootstocks ( Vitis spp. hybrids) and a V. vinifera variety by phylloxera ( Dactylosphaera vitifolii SHIMER) was assessed in standardised glasshouse trials in New Zealand and Germany. The roots of 420 A rootstock and the V. vinifera variety Muller-Thurgau were readily galled by New Zealand phylloxera but little or no galling occurred on the other rootstocks (SO 4, 3309 C, 1202 C, ARG 1). No leaf galling reaction occurred. When the same New Zealand grapevine material was infested with a German population of phylloxera in Germany, the roots and leaves of all cultivars except 420 A and 1202 C were readily galled. This variation in the plant galling reaction by the two phylloxera populations is considered as evidence of the existence of different phylloxera biotypes between New Zealand and Germany. Furthermore, when the same cultivars, but of German origin, were infested with German phylloxera, the leaves and roots of a ll except ARG 1 and 420 A were readily galled suggesting clonal differences in rootstocks between the two countries.