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Relative Differential Efficiency of Buds and Root Chips in Transmitting the Causal Agent of Peach Stem Pitting and Incidence of Necrotic RingSpot Virus in Pitted Trees. Srecko M. Mircetich, Research Plant Pathologist, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705; E. L. Civerolo(2), and H. W. Fogle(3). (2)(3)Research Plant Pathologist and Horticulturist, respectively, Plant Science Research Division, ARS, USDA, Beltsville, Maryland 20705. Phytopathology 61:1270-1276. Accepted for publication 31 May 1971. DOI: 10.1094/Phyto-61-1270.

Causal agent(s) of stem pitting was transmitted readily by root chips and erratically by buds from naturally infected peach, nectarine, and Prunus davidiana trees into peach seedlings. Likewise, graft-transmission of the stem pitting causal agent(s) from experimentally infected peach seedlings was effected readily by root and stem chips collected within 30 cm from the original graft inoculum. However, buds 96-113 cm distant from the pitted area from the same source failed to induce stem pitting in the indicator plants. Apparently, peach stem pitting causal agent(s) may not be distributed uniformly in the infected trees. All symptoms of the disease were reproduced in the graft-inoculated indicator plants in the greenhouse within 5 months after inoculation. These investigations revealed a high incidence of necrotic ringspot virus (NRSV) in pitted peach trees in commercial orchards. However, there was no correlation between the presence of NRSV and stem pitting or the severity of stem pitting symptoms in naturally or experimentally infected peach trees. NRSV failed to induce stem pitting in artificially inoculated peach seedlings. Therefore, the results suggest that NRSV apparently is not the primary cause of peach stem pitting.

Additional keywords: Prunus persica, P. armeniaca, virus disease.