No evidence of superclones in leaf-feeding forms of austrian grape phylloxera (Daktulosphaira vitifoliae)

Abstract

The genetic structure of ten grape phylloxera populations, sampled in summer of 2006 and 2007 from four distinct viticultural areas in Austria, Daktulosphaira vitifoliae (Fitch) (Homoptera: Phylloxeridae) was analyzed using six SSR markers (Dvit1-Dvit6). Leaf-feeding populations were chosen from similar ecological habitats, where susceptible rootstock hosts have overtaken scions in abandoned vineyards and produce grape phylloxera populations. To study population structures and test for dominating genotypes, population genetic measures were performed. The genetic diversity detected within the entire set of 315 genotypes was high, with 223 distinct multilocus genotypes (MLGs). Excess of heterozygotes and significant deviations from Hardy-Weinberg equilibrium in some populations indicated that the major reproduction mode in these populations is asexual but, sexual reproduction also confirmed by the sign. P sex values. The genetic diversity within populations was higher than between populations, although only three overlapping genotypes could be found. MLGs were rare, indicating that no candidate for superclones were detected in the leaf-feeding populations studied.

Deployment of organic farming at a landscape scale maintains low pest infestation and high crop productivity levels in vineyards

“…This scale of response depends on functional attributes, such as the dispersal ability, of the species and on the structure of the landscape itself. The most important scales found in our study for these three pest taxa are consistent with available information on their dispersal abilities (Forneck, Anhalt, Mammerler, & Griesser, 2015;Grasswitz & James, 2008). Moreover, our results corroborate those of recent studies in perennial crops in which the beneficial effects of semi-natural habitats on pest control were greatest at relatively small spatial scales (<250 m radius) (Henri et al, 2015;Thomson & Hoffmann, 2013).…”

Grape phylloxera (Daktulosphaira vitifoliaeFitch) in Argentina: ecological associations to diversity, population structure and reproductive mode

“…As previously found in other regions (Vorwerk and Forneck , , Islam et al , Forneck et al , Riaz et al ), the parthenogenetic nature of the insect in Argentina is confirmed by P sex values, the excess of heterozygous individuals and the significant deviations from the Hardy–Weinberg equilibrium. The possible occurrence, however, of sporadic sexual reproduction cannot be discarded.…”

First European leaf-feeding grape phylloxera (Daktulosphaira vitifoliae Fitch) survey in Swiss and German commercial vineyards

“…Tests of the Hardy-Weinberg equilibrium showed the presence of an excess of heterozygosity (F is < 0) in some of the populations. The F is values observed in the commercial vineyard populations are less (negatively) consistent within populations than those previously reported in studies performed in Bsemi-native habitats^, including abandoned rootstock areas with extensive leaf galling populations, research grapevine collections or rootstock nurseries (Forneck et al 2015;Vorwerk and Forneck 2007). MLGs were observed in each sampling region (Supplement Table 1), indicating anholocyclic reproduction in commercial vineyards on both leaves and roots.…”

“…In parallel, a principal component analysis was performed by means of the DARwin software (Perrier and Jacquemoud-Collet 2006). Allele frequencies, mean number of alleles per locus, observed heterozygosity (Ho) and unbiased estimates of heterozygosity expected under Hardy-Weinberg assumptions (He) were calculated as previously indicated (Forneck et al 2015). Clonal diversity (k) within populations was calculated for each population as k = G/N, where G is the number of different multilocus genotypes present in the sample and N is the sample size.…”