Search

Grape phylloxera, Daktulosphaira vitifoliae FITCH (Hemiptera, Phylloxeridae) is a notorious pest in viticulture. The insect feeds on roots and leaves of grapevines where it induces nodosities and tuberosities on roots and pocketlike galls on roots and leaves of grapevines. As an effective plant protection against phylloxera, resistant rootstocks are used worldwide in viticulture. In contrast to successful research efforts targeting root resistance, knowledge on the resistance in leaves is still limited. From the eight genetic loci published (Rdv1-8), one (Rdv3) could be characterized as relevant for leaf resistance. Moreover, phylloxera resistance in grapevine leaves seems to rely on several interacting QTLs. Foliar infestations in commercial vineyards on V. vinifera occur rarely, although leaf galls on cultivated cold-hardy or fungi-tolerant hybrids may frequently occur in commercial viticulture. As to date, studies of the damage of phylloxerated foliage on the yield and quality have provided no unambiguous results, and management options remain limited. A knowledge gap remains with regard to the genetic background and environmental constraints on the leaf resistance (or susceptibility) towards grape phylloxera which include the insects' genotype(s) and feeding performance (biotypes). In this article, we present a short review of the most urgent questions from our research on controlled studies of the phylloxera-leaf interaction. [ABSTRACT FROM AUTHOR]

In the present study the effect of flavonoid compounds on the germination and fungal growth of the soil-borne tomato pathogen Fusarium oxysporum f. sp. lycopersici was studied. Out of 12 flavonoid compounds only myricetin and luteolin exhibited a low stimulating activity on microconidia germination of Fusarium oxysporum f. sp. lycopersici, whereas the other flavonoids tested were inactive when applied at five different concentrations. In our study the tested flavonoids affect fungal growth differently to microconidia germination. Individual flavonoid concentrations resulted in a small increase of fungal growth, but the lowest flavonoid concentrations showed an inhibiting effect on fungal growth for all flavonoids tested. There is evidence to suggest, that low flavonoid concentrations exhibit slight antimicrobial properties against Fusarium oxysporum f. sp. lycopersici. [ABSTRACT FROM AUTHOR]

In this study we assessed microconidia germination of the tomato pathogens F. oxysporum f. sp. lycopersici ( Fol ) and F. oxysporum f. sp. radicis-lycopersici ( Forl ) in the presence of root exudates. Tomato root exudates stimulated microconidia germination and the level of stimulation was affected by plant age. Treatment of root exudates with insoluble polyvinylpolypyrrolidone, which binds phenolic compounds, indicated that tomato root exudates contain phenolic compounds inhibitory to F. oxysporum microconidia germination. Our study indicates that tomato root exudates similarly stimulate microconidia germination of both Fol and Forl . However, individual F. oxysporum strains differ in the degree of germination response to the root exudates. Furthermore, root exudates from non-host plants also contain compounds that stimulate microconidia germination of Fol . In general, the effects of root exudates from non-host plants did not differ considerably from those of tomato. The ability of phenolic compounds to inhibit germination of Fol seems not to be plant-specific. [ABSTRACT FROM AUTHOR]