|LINDO, ALIZA - University Of The West Indies|
|ROBINSON, DWIGHT - University Of The West Indies|
|TENNANT, PAULA - University Of The West Indies|
Submitted to: Tropical Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/1/2018
Publication Date: 5/9/2018
Citation: Lindo, A.A., Robinson, D.E., Tennant, P.F., Meinhardt, L.W., Zhang, D. 2018. Molecular characterization of farmer selections of cacao (Theobroma cacao) from Jamaica using Single Nucleotide Polymorphism (SNP) markers. Tropical Plant Biology. https://doi.org/10.1007/s12042-018-9203-5.
Interpretive Summary: Cacao is an economically important commodity in Jamaica and knowledge of the genetic diversity in Jamaican cacao germplasm is essential for it conservation, management and use. Almost nothing is known about the genetic diversity of cacao in Jamaica other than the historical records of its introduction. To address this problem the two main germplasm collections and on-farm genetic diversity was assessed. The analysis demonstrated that most of the tested Jamaican cacaos were hybrids derived from five original germplasm groups and that both germplasm collections and in farmer's field had several diversity gaps, especially with regards to disease resistance to cacao frosty pod rot, a severe cacao disease recently found in Jamaica. These findings will be used by researchers and cacao breeders, extension staff and farmers to improve cacao production in Jamaica and other Caribbean islands.
Technical Abstract: Cacao is an economically important commodity in Jamaica. Knowledge of the genetic diversity in Jamaican cacao germplasm is essential for their conservation and management. In spite of cacao's economic importance in Jamaica, the crop is understudied therefore limiting sound decisions towards improving productivity. Assessment of germplasms and on-farm genetic diversity is required to assist selecting superior genotypes to propagate and distribute across the island, as well as using them as parental clones in breeding programs. Using 94 SNP markers, 140 Jamaican cacao samples from germplasm collections and a farmer’s field along with 150 reference samples was analyzed. The Principal coordinates analysis demonstrated that majority of the Jamaican cacao selections were hybrids derived from five original germplasm groups, including Criollo, Amelonado and three Upper Amazon Forastero groups. The Bayesian clustering analysis revealed that the Parinari (PA) ancestral lineage contributed the most (29.9%) to the Jamaican cacao germplasm. The germplasm collections showed greater ancestral contributions compared to the farmer’s field, but the genetic differentiation between the three collecting sites was not significant, indicating all three sites originated from the same seed gardens. The current study supports the historical records and revealed that Jamaican cacao hybrids are derived from crosses between Upper Amazon varieties and Amelonado and Trinitario varieties. Although the majority of the cacao genetic groups were observed in the Jamaican cacao collections several diversity gaps were found in both germplasm collections and in farmer's field, especially germplasm with disease resistance to cacao frosty pod rot that was recently found in Jamaica.