Psorosis-Like Agents Prevalent in Rio-Grande Gummosis-Affected Ruby Red Grapefruit Groves and Grapefruit Budwood Sources

R. R. Lee, C. A. Powell, R. R. Pelosi, R. M. Sonoda


Budwood was collected from healthy-appearing and Rio-Grande Gummosis (RGG)-affected Ruby Red grapefruit trees from 5 different groves, 13-40 years of age, in the Indian River region of Florida. Similar collections from trees used as scion sources for grapefruit propagation were made at 6 different nurseries. Indexing of the budwood on Madam Vinous sweet orange seedlings under a cool night, warm day temper ature regime resulted in the appearance of oakleaf and mild vein-clearing patterns, indicative of infection with a psorosis-like agent, for 75% and 15% of the budwood from the commercial production and scion groves, respectively. We conclude that some Florida grapefruit budwood sources are contaminated with a psorosis-like agent that has resulted in widespread distribution of the agent in Florida's commercial grapefruit.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283