Responses of potato cultivars (Solanum tuberosum) to infection with Cucumber mosaic virus isolated from different host species

Eight isolates of Cucumber mosaic virus (CMV) isolated from seven different host species were tested for their virulence on potato cv. Desirée. Three isolates caused a systemic infection, of which one isolate from Asiatic lily (CMV-P26) and one from cucumber (CMV-J) appeared to be highly virulent, in contrast to the third isolate (CMV-M) that originated from cucumber and caused mild symptoms only. These three isolates were transmitted to 26 additional potato cultivars by mechanical inoculation in a greenhouse. All cultivars were infected with at least one CMV isolate and developed local chlorotic symptoms, but only 17 cultivars (including Desiree) developed primary systemic symptoms including necrosis, mosaic and/or malformation of leaves. Furthermore, in only five cultivars (including Desiree) CMV was transmitted to tubers and was subsequently detected in plants of the first and second vegetative progeny, the secondary symptoms of these plants being severe. The observed phenotypic responses of potatoes to CMV were not associated with the maturity type (early or late) or resistance to other viruses. Results of this study indicate a high level of biological variability among CMV isolates and that infection in potato depends on CMV isolate and potato cultivar.     

Influence of Different Carbon Sources on Invertase Activity and Growth of Sour Cherry (Prunus cerasus L.) Shoot Cultures

The influence of different sugars on shoot multiplication invitro and on the activity of invertase was studied with sourcherry (Prunus cerasus L.) cultures. The sugars sucrose, glucoseand fructose, and the sugar alcohol sorbitol, were investigatedat a wide range of concentrations. The optimum concentrationsof all carbon sources were 2% and 3% (w/v). Sucrose and glucosefavoured a similar rate of proliferation. However, in the presenceof fructose, proliferation was lowest but was coupled with thehighest frequency of formation of long shoots. The highest activityof total invertase was for tissues growing on a sucrose-containingmedium while, in a sugar-free medium, invertase activity wasmainly found in the ‘salt extracted’ fraction. Inthe remaining treatments, ‘soluble invertase’ dominated.For each sugar investigated, the activity of both forms of invertasewas significantly higher at 2% than at 3% (w/v) sugar. Key words: Tissue culture, sugars, invertase, shoot multiplication, sour cherry