|Schnell Ii, Raymond|
Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/29/2004
Publication Date: 1/1/2005
Citation: Schnell II, R.J., Olano, C.T., Brown, J.S., Meerow, A.W., Meneres, T., Nagai, C., Motamayor, J.C. 2005. Retrospective determination of the parental population of superior Theobroma cacao L. seedlings and association of microsatellite alleles with productivity. Journal of the American Society for Horticultural Science. 130(2):181-190. Interpretive Summary: Commercial cacao production in Hawaii is increasing. The diverse agricultural environments on the islands provide the opportunity to develop unique flavors in the beans producing specialty chocolate that commands premium prices. Cacao was first introduced for commercial planting around 1980 and seed from these introductions is being used for commercial plantings. A high percentage of productive seedlings were observed at the old Waialua Sugar Plantation on Oahu but the seed source for these productive plants was uncertain. Using molecular markers called microsatellites we were able to determine that the parents of the productive seedlings came from the University of Hawaii experiment station at Waimanalo and not from two other locations where seed was known to have been collected. We identified the parents of the productive clones and were able to associate some of the markers with productivity of the plants. These markers may be helpful in future studies when selecting for improved production. The identified parents and productive seedlings can now be used to produce new populations to select for increased productivity and enhanced flavor characteristics.
Technical Abstract: Commercial production of cacao in Hawaii is increasing and this trend is expected to continue over the next several years. The increased acreages are being planted with seedlings from introduced and uncharacterized cacao populations. Using microsatellite markers, we analyzed the parental populations to identify the candidate parents and determine basic genetic characterization for 99 productive and 50 unproductive seedlings growing on the old Waialua Sugar Plantation. At least three introductions of cacao have occurred in Hawaii. The parents of productive and unproductive seedlings at Waialua were believed to be the population at the Hawaiian Agricultural Research Center (HARC) at Kunia; however, potential parental populations also exist at University of Hawaii (UH) research stations at Waimanalo and Malama Ki. Based on 19 polymorphic microsatellite loci the parental population was identified as trees from the UH research station at Waimanalo and not trees from Malama Ki or Kunia. The Kunia and Malama Ki populations were very similar with low allelic diversity (A=1.92) and low unbiased gene diversity (Hnb) of 0.311 and 0.39 respectively and are Trinitario in type. The Waimanalo, productive seedling, and unproductive seedling populations had much higher levels of genetic diversity with Hnb of 0.669, 0.686, and 0.686 respectively and are Upper Amazon Forastero hybridized with Trinitario in type. Only 20 individuals remain from the original Waimanalo planting and most of these contributed to both the productive and unproductive seedling populations in equal proportions. An additional 18 microsatellite markers were run on the Waimanalo, productive, and unproductive populations for a total of 37 loci. Seven loci had alleles that were associated with productive or unproductive seedlings using Armitage's trend test and may prove useful in future evaluations. Based on these results the distribution of seed from the Kunia population for commercial planting is not recommended. The material at UH-Waiminalo will be used for further full-sib family production and as the basis for a recurrent selection program for increased productivity and enhanced flavor characteristics.