Genetic diversity in the USDA-ARS National Clonal Germplasm Repository, Davis, California fig germplasm collection

Authors: Preece, John; Aradhya, Mallikarjuna

Submitted to: Acta Horticulturae
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/25/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary: The USDA-ARS National Clonal Germplasm Repository, Davis, CA USA curates the national fig collection. Currently, there are 124 accessions available for distribution to the national and international scientific community to support research. Phenotypically, most of the figs in the collection ripen green or yellow with a few that ripen black or red; most have red flesh. Capri and edible figs are interplanted or in close proximity, so the collection is caprified each year, resulting in brighter colored and sweeter figs than parthenocarpic ripe synconia. Including the 124 figs available for distribution plus those too small to distribute, 15 microsatellite markers were used to analyze the amount and pattern of distribution in the collection consisting of 194 F. carica, one F. palmata, and one interspecific hybrid accessions. Neighbor-joining cluster analysis revealed 10 genetic groups within the collection, but does not strictly discriminate different fig types – Smyrna, Common, San Pedro, and Capri. Substantial polymorphism and marginal differentiation was evident within the fig collection, suggesting that fig circulates genetic variability across different fig types through a mutation-recombination process facilitated by the symbiotic relationship between fig and its pollinator. Most groups identified in the CA and PCA possessed an excess of heterozygosity as figs were selected for high heterotic vigor and great adaptation as commonly observed among clonally propagated plants.

Technical Abstract: The USDA-ARS National Clonal Germplasm Repository, Davis, CA USA curates the national fig collection. Currently, there are 124 accessions available for distribution to the national and international scientific community to support research. Phenotypically, most of the figs in the collection ripen green or yellow with a few that ripen black or red; most have red flesh. Capri and edible figs are interplanted or in close proximity, so the collection is caprified each year, resulting in brighter colored and sweeter figs than parthenocarpic ripe synconia. Including the 124 figs available for distribution plus those too small to distribute, 15 microsatellite markers were used to analyze the amount and pattern of distribution in the collection consisting of 194 F. carica, one F. palmata, and one interspecific hybrid accessions. Neighbor-joining cluster analysis revealed 10 genetic groups within the collection, but does not strictly discriminate different fig types – Smyrna, Common, San Pedro, and Capri. Substantial polymorphism and marginal differentiation was evident within the fig collection, suggesting that fig circulates genetic variability across different fig types through a mutation-recombination process facilitated by the symbiotic relationship between fig and its pollinator. Most groups identified in the CA and PCA possessed an excess of heterozygosity as figs were selected for high heterotic vigor and great adaptation as commonly observed among clonally propagated plants.