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World of CitrusWorld of CitrusXXX-639
Jude Grosser, Manjul Dutt, and Fred Gmitter · Citrus Industry Magazine · 2022-07-18
The web page displays Josh McGill as its byline and credits Jude Grosser, Manjul Dutt, and Fred Gmitter as article authors. In “XXX-639 MUTANT,” they report that one vigorous X-639 rootstock within an HLB-positive Valencia field planting was recovered as a mutant rootstock. SSR marker analysis matched standard X-639; flow cytometry showed less measurable DNA and suggested possible deletion mutations. The article says the recovered rootstock tested negative for CLas and propagations were underway for advanced trials. This is an early report, not a replicated performance result or general HLB-resistance conclusion. The nearly 50 fruit were borne on the unusual field tree; the article does not report fruit borne by XXX-639 scions.
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Dr. Jude Grosser · SWFREC · 2025-03-04
https://www.youtube.com/watch?v=H_0RhIVHpKw (opens in a new tab)
Summary from transcript: In this auto-captioned SWFREC seminar, Dr. Jude Grosser describes a putative mutant of commercial X-639 rootstock; the slide at 44:14 labels it “x639 mutant STR-4-1.” The account concerns infected Valencia on five rootstocks from a nutrition experiment and a reset planting (44:06–44:54). One Valencia scion on X-639 rootstock later grew unusually vigorously and carried about 50 Valencia fruit (45:03–45:21). The speaker reports recovering the tree, possible missing DNA by flow cytometry, 13 SSR markers matching X-639, and sequencing that yielded mutations (45:23–47:10). The presentation does not name XXX-639. This account may describe the mutant selection called XXX-639 in the July 2022 Citrus Industry report, but that connection is an inference, not an identification made in the video; it is not a replicated performance trial.
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