Interaction between relative humidity and resistance to Dasineura tetensi in blackcurrant
1 Infestation by the blackcurrant leaf midge Dasineura tetensi and galling incidence on a susceptible (cv. ‘Öjebyn’) and a moderately resistant (cv. ‘Storklas’) blackcurrant genotype was studied in the field for two midge generations in the same growing season. On the resistant genotype gall initiation is delayed.
2 The relation between infestation and galling incidence showed considerable variation between the two generations. Galling symptoms produced by the second midge generation were weak on the resistant as compared with the susceptible blackcurrant.
3 Because larval development of that generation coincided with a period of dry and warm weather, it is possible that larvae on the resistant genotype suffered desiccation to a greater extent than larvae on the susceptible genotype where gall development was stronger.
4 The possible interaction of relative humidity and expression of resistance was investigated in controlled environment experiments. The resistant ‘Storklas’ and a susceptible (‘7801–31’) currant genotype were studied at two constant relative humidities, 30 and 70%.
5 Larvae of D. tetensi suffered from higher mortality and reduced growth rate on both genotypes in the low humidity environment.
6 There was also a significant plant genotype by humidity interaction on larval performance; no galls were produced and no larvae completed development on the resistant currant at low humidity.
7 There was a trend for a positive correlation between larval length and larval density on a plant at low humidity but not at high humidity.
Document Type: Research Article
Affiliations: Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences (SLU), PO Box 4097, S-904 03 Umeå, Sweden
Publication date: 2001-08-01