Genetic diversity revealed by microsatellites in genus Carya

Authors: Wang, Xinwang; Chatwin, Warren; Hilton, Angelyn; Kubenka, Keith

Submitted to: Forests
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2022
Publication Date: 1/26/2022
Citation: Wang, X., Chatwin, W.B., Hilton, A.E., Kubenka, K.A. 2022. Genetic diversity revealed by microsatellites in genus Carya. Forests. 13. Article 188. https://doi.org/10.3390/f13020188.
DOI: https://doi.org/10.3390/f13020188

Interpretive Summary: Pecan is the most economically important member of the hickory genus in the Juglandaceae. The breeding of new cultivars has been accomplished for more than 80 years in the USDA Pecan Breeding Program. As a result, nearly 30 cultivars with improvement of nut quality and disease resistance have been released since the 1930's. Except for the constraints of its longevity and big tree size, narrow genetic background is another factor to slow down the process of new cultivar development. Exploration of new traits from related species in the genus Carya is the most urgent and effective strategy to expand genetic background, in order to introduce new traits into modern pecan cultivars. Wide genetic diversity in related species provides such opportunity for pecan breeders. This study used microsatellites or SSR markers to evaluate the genetic diversity among the species in the genus Carya. The results provide insights to utilize diverse genetic germplasm in our breeding program.

Technical Abstract: The genus Carya consists of 17 species that are divided into 3 sections: Carya or the true hickories, Apocarya or the pecan hickories, and Sinocarya or the Asian hickories. Interspecific hybrids among the species in the 3 sections exist and have been used in pecan cultivar development. Nuclear and plastid microsatellite or SSR markers have been useful in distinguishing species, sections, and populations. They provide evidence for hybridity between species and can confirm heredity within crosses. As more sophisticated methods of genomic evaluation are cooperatively developed for use in pecan breeding and selection, the use of these methods will be supplemented and informed by the lessons provided by microsatellite markers, as interpreted across broad germplasm collections. In this study, over 400 Carya accessions from diverse diploid and tetraploid taxa and their interspecific hybrids were analyzed using 14 nuclear and 3 plastid microsatellite markers. Molecular profiles were converted to binary form, associated with taxonomic and geographic classification descriptors, and subjected to principal component analysis. Taxonomic classifications at levels from genus, section, and species were confirmed, along with patterns of interspecific hybridity. Evidence was also found of genetic differences associated with geographic distribution. The results indicate that this group of markers is useful in examining and characterizing populations and hybrids in the genus Carya and may help delineate the composition of a core collection to help characterize the repository collection for use in a pecan breeding program.