Determination of Sour Orange Rootstock by Paper Chromatography

‘QUICK decline’, a devastating virus infection of orange trees, was first found to be present in southern California in 1939, and by 1952 it had spread to six of the fourteen counties in which oranges are grown in California. Inoculation tests 1 demonstrated that tolerance to the virus varies with the variety of the rootstock on which the sweet orange is growing, and that the disease is likely to be fatal only if the rootstock is that of the sour orange ( Citrus aurantium L.). Because of this scion-rootstock relationship to the seriousness of the disease, which in one form or another is widely spread throughout the citrus-growing areas of the world, a method for the detection of the sour orange rootstock in established orchards is of considerable significance.