Vitis 41 (2), 9397 (2002) Histochemistry and anatomy of phylloxera (Daktulosphaira vitifoliae) nodosities on young roots of grapevine (Vitis spp). A. FORNECK 1) , S. KLEINMANN 1) , R. BLAICH 1) and S. F. ANVARI 2) Universität Hohenheim, Institut für Obst-, Gemüse- und Weinbau, 1) Fachgebiet Weinbau (370a), 2) Fachgebiet Obstbau (370b), Stuttgart, Deutschland Correspondence to: A. FORNECK, Universität Hohenheim, Institut für Obst-, Gemüse- und Weinbau, Fachgebiet Weinbau (370a), Emil- Wolff-Straße 25, 70593 Stuttgart, Germany. Fax: +49-711-459-3946. E-mail: aforneck@uni-hohenheim.de Summary Phylloxera (Daktulosphaira vitifoliae FITCH) induce galls (nodosities) on young grapevine roots. Histological and histochemical methods were applied to study the galls morphology and enzyme activities (peroxidases, leucine aminopeptidases and acidic phosphatases). Susceptible V. vinifera cv. Cabernet Sauvignon was compared to the resistant rootstock 5 BB (V. berlandieri x V. riparia) using aseptic dual culture conditions. The gall induction phase was analyzed before visible signs of potential resistance responses were detected. Elevated metabolic activity has been found in nodosities compared to uninfected roots. Starch granule incorporation was detected in young galls and was highest at the feeding site. As galls mature, the starch density decreased at the feeding site and increased towards the periphery of the gall. Peroxidase, acidic phosphatase and leucine aminopeptidase activities were highest at the incision. No differences in enzyme activities could be detected between the two cultivars tested. K e y w o r d s : Vitis vinifera, rootstock, phylloxera, nodosity, resistance, gall formation, host-parasite interaction. Introduction Grape phylloxera, Daktulosphaira vitifoliae FITCH (Hemiptera: Phylloxeridae), are gall forming aphids native to North America and monophagous on grape (DAVIDSON ans NOUGARET 1921). After being introduced into Europe in the middle of the 19th century, D. vitifoliae spread and destroyed vineyards planted with Vitis vinifera L. (Vitaceae). The breeding of rootstocks based on American Vitis species with resistant roots led to the eventual recovery of European viticulture. D. vitifoliae forms pocket-like galls on leaves and hooked galls on root tips (nodosities). Feeding and gall development on lignified parts of grape roots cause crac- king and enables attack by soil-borne pathogens which can result in host plant death (GRANETT et al. 2001). Phylloxera depend on specific feeding tissue (galls) during their entire life cycle. First-stage D. vitifoliae penetrate the meristematic zones of root tips with their rostrum (stylet bundle) and stay sedentary until adulthood. Probably as a result of salivary secretions, root cells close to the feeding site become polyploid, whereas cells far from the feeding site enlarge and seem to be used as food deposit until completion of phylloxeras life cycle (4-6 weeks later). Morphological studies of nodosities illustrate the anatomy of the root galls which contain hypertrophic and hyperplastic cells (MILLARDET 1898, NIKLOWITZ 1955, KLEINMANN 2001) and polyploid cell nuclei (ANDERS 1960). Cells close to the feeding site decrease in size and paren- chymal cells on the opposite side of the vascular tubes en- large and contain starch granules. Other authors studied the biochemical composition of nodosities (e.g. STOEV 1966, RILLING 1974, 1975). SCHÄFER (1985) found increased starch deposits, soluble proteins and phenolic substances in no- dosities and KELLOW et al. (2000) detected higher amounts of amino acids except asparagine in nodosities if compared to uninfected root tips. However the protein composition detected in SDS gels showed no differences between in- fected and non-infected tissue. Generally the nodosity acts as strong physiological sink as postulated by STEFFAN and RILLING (1981), though their results suggest that trans- portation of carbohydrates is restricted within the root. In this study, the anatomy of nodosities on two cultivars differing in their resistance to phylloxera was compared to non-infected root tips in an aseptic culture system, which facilitates histochemical and molecular genetic studies. Such a system excludes interfering factors that may result in arti- facts and allows precise inoculation and controlled feeding time. To better understand the events that take place during the early steps of feeding site development and gall induc- tion we applied histochemical techniques to monitor cellular enzymatic expression and morphological changes within phylloxera-induced root galls. Material and Methods V i t i s x p h y l l o x e r a i n t e r a c t i o n : In vitro- propagated Vitis vinifera cv. Cabernet Sauvignon and the rootstock Kober 5 BB (V. berlandieri x V. riparia) were co- propagated with a laboratory-raised strain of D. vitifoliae in an aseptic dual system previously described (FORNECK et al. 1996). Samples of root galls were taken by dissecting no- dosities (2-6 day old) including the associated D. vitifoliae, according to the galls developmental stages. Uninfected root tips were gathered from non-infected, separated in vitro plants.