Evaluation of virus eradication by a colloidal silver solution under In Vitro Conditions

One of the reasons for the low-yielding potato cultivar is related to the limited use of the virus free potato seeds in the country. Lack of knowledge about certified potato seeds, weak seed potato _production system and finally unstable price of commercial potato and insufficient seed purchasing funding available for farmers are the underlying reasons for low potato yields. Since most the fungi and bacteria produce visual symptoms on potato tubers, they are usually discarded before planting. However, there is no virus symptoms can be detected on tubers, therefore during planting, their yield degradation impacts is unavoidable. Objectives of this study are to evaluate effectiveness of colloidal silver solutions in eradicating some of most prevailing virus on some potato cultivars in the country. Agria, Safron and Almera was sampled from contaminated potato fields because of their larger area coverages from provinces. Their sprouted tubers were planted in potting soil and after enough shoot growths, samples of shoot from each cultivar was cut and surface sterilized and transferred on the MS growth media. After producing enough numbers of propaguls, at least 30 uniform nodule-cuttings consisting of 2 to 5 mm lengths were transferred into MS growth media including 0, 25, 100, 200, 300, 400, 500 and 600 ppm of colloidal silver solutions and incubated for 30 days. Optical densities (OD) of extracts taken from newly developed leaves and their phenotypical characteristics of each treated plantlets were analyzed applying Proc ttest from SAS package and means were compared to their related controls at 5% probabilty. Generally, addition of colloidal silver to the growth media of potato In Vitro plantlet taken from Agria, Safron and Almera cultivars were effective in reducing OD of the plant-extracts recorded in the ELISA test. It is expected that subculturing of the plantlets under similar treatments finally render virus free plants for commercial productions. The most effective concentration of the colloidal silver solutions depends on the type of potato cultivar. The most OD reductions (77% and 84%) for PVY of Safron and Almera cultivars were respectively recorded at 400 and 200 ppm treatments compared to the control ODs and the highest reduction (56%) for PLRV of Agria was at 300 ppm. Their phenotypical traits such as shoot and root lengths were reduced compared to the control plantlets under treatments. In contrast, leaf area of the treated plantlets compare to the control plantlets were significantly improved. Variations in responses to the treatments may be related to use of the plantlets with differing basal concentrations of viruses. This is related the variation exists in different plant tissues (socalled somocolonal variations)