Citrus halimii was published as a new Citrus species by Stone et al (1973) although, according to Bill Bitters (letter dated April 15, 1983 on file to David Jones) "No way can [Ben Stone] convince me that C halimii is a valid species". Indeed. There are currently 3 accessions of Citrus halimii maintained at Riverside: PI 539196, PI 539197, and PI 600639. Information on archival accession card states the source of PI 539196 as "Scora - Malaysia". However, Stone et al (1973), after listing locations of specimens examined, state "In 1971 Lowry and Scora visited the Genting Sempah tree...some seedlings have been grown at the Citrus Research Center, University of California, Riverside." Therefore, information from Stone et al (1973) has been incorporated into the Source information. PI 539197 and PI 600639, although donated at different times by different persons, are apparently from the same source. SSR maker analysis, performed in the laboratory of Prof Mikeal Roose, University of California, Riverside by summer intern Leonardo Lara indicated that all three accessions are genetically identical. A total of 12 trees from the 3 accessions were identical at all loci using 9 markers. This is interesting, as all are seedlings and C halimii is monoembryonic (Stone et al, 1973). I recall a number of years ago, somebody from Florida (possibly Fred Gmitter) called asking about this, as all their seedlings appeared to be identical. Indeed.
It therefore appears that all C halimii at Riverside are identical. As noted by Ed Nauer, it does not do well under our Riverside conditions. When planted in Irvine, the trees do somewhat better but are still sensitive to Southern California winter temperatures. They do, however, set fruit and seed. (RR Krueger, 02/26/2013)
Information and lovely pictures of PI 539196 [= RCRC 3780] from the University of California, Riverside Citrus Variety Collection are available here.