Variation in performance on two grape cultivars within and among populations of grape Phylloxera from wild and cultivated habitats

Abstract

When an indigenous insect becomes a pest, comparisons of performance of pest and non-pest populations on crop plants and of genetic variation in that performance may provide insight into the evolution of pest populations. To measure such genetic variation, 8-15clones of the grape phylloxera (Daktulosphaira vitifoliae Fitch) were collected from wild grapevines in each of 3 geographically isolated sites (populations) and from commercial vineyards in northern California. A complete life table was made for clonal replicates from populations collected from wild grapevines on each of two commercial grape cultivars, the susceptible Vitis vinifera (L.) cultivar Cabernet Sauvignon, and the phylloxera-resistant rootstock 'AxR # 1'. Variation in mean performance on these two hosts was partitioned among clones within collection sites and among sites. Performance measures included an individual analog to the intrinsic rate of increase (r), age at first oviposition, fecundity in the first ten days of reproduction, total fecundity, and longevity. The overall performance of phylloxera from the wild grapevines on the resistant cultivar AxR # 1 was greater than or equal to that on the susceptible cultivar Cabernet Sauvignon. There was significant variation among clones within populations from wild grapes in the rate of increase on 'AxR# 1' and marginally significant clonal variation in some of the component parameters. There was no significant variation among clones within populations on 'Cabernet Sauvignon' and no significant differences between populations on either crop in any trait.In a second experiment we compared the relative performance of 15-17 clones from wild grapevines and from commercial vineyards when reared on 'Cabernet Sauvignon' and 'AxR # 1'. Phylloxera from commercial vineyards had much higher overall performance on 'Cabernet Sauvignon' than did phylloxera from the wild grapevines. Phylloxera from the commercial vineyard also had higher performance on 'Cabernet Sauvignon' than on 'AxR' 1' but the performance of the phylloxera from wild and commercial grapes did not differ on 'AxR # 1'.Our results show that there is genetic variation in traits related to performance on a resistant rootstock within these indigenous non-pest populations of phylloxera, but not among them. The pattern of performance of pest and non-pest populations on two commercial cultivars suggests that current levels of phylloxera performance on crop cultivars are the result of adaptation to those cultivars which has occurred while phylloxera has been associated with viticulture. Implications of these results for understanding the recent adaptation of phylloxera to 'AxR# 1' in California are also discussed.

Genetic structure of an introduced pest, grape phylloxera (Daktulosphaira vitifoliaeFitch), in Europe

“…Phylloxera clones have adapted to new hosts as judged by altered performance or feeding preference (Hawthorne and Via 1994;Forneck et al 1998). Correlation between these adaptive changes and molecular data has not yet been found.…”

Reproductive mode of grape phylloxera (Daktulosphaira vitifoliae, Homoptera: Phylloxeridae) in Europe: molecular evidence for predominantly asexual populations and a lack of gene flow between them

“…The development of resistant grapevine rootstocks bred from North American species enabled the redevelopment of European viticulture, as V. vinifera cultivars were grafted onto resistant rootstocks. Native D. vitifoliae populations showed varying performance in adapting to new host plants (Downie 2000;Downie et al 2001;Hawthorne and Via 1994;Forneck et al 2001). An association of aphid genotypes with specific host plants has been demonstrated in Australian D. vitifoliae clones (Corrie et al 2003) and on European clonal lineages in greenhouse studies (A. Ritter, S. Vorwerk, A. Forneck, unpublished).…”

Fine-scale genetic structure of grape phylloxera from the roots and leaves of Vitis

“…In a population comprising of genetically diverse clones, the fittest clone(s) for an environment is expected to dominate over time, and genetic variability is therefore predicted to be lower in a homogenous environment (Vrijenhoek, 1979;Weeks and Hoffmann, 1998). Differential fitness on host plants has been noted previously between grape phylloxera populations (Granett et al, 1987;Hawthorne and Via, 1994;Forneck et al, 2002). Most recently, by directly examining the distribution of genotypic classes in vineyards with adjacent rows of different rootstocks, Corrie et al (2003) showed strong associations between grape phylloxera clonal lineages and vine host type within a vineyard.…”