Color analysis of storage roots from the USDA, ARS sweetpotato germplasm collection

Authors: Jackson, D; Harrison Jr, Howard; Jarret, Robert - Bob; Wadl, Phillip

Submitted to: Genetic Resources and Crop Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2018
Publication Date: 2/9/2018
Citation: Jackson, D.M., Harrison Jr, H.F., Jarret, R.L., Wadl, P.A. 2018. Color analysis of storage roots from the USDA, ARS sweetpotato germplasm collection. Genetic Resources and Crop Evolution. 65(4):1217-1236. https://doi:10.1007/s10722-018-0609-6.
DOI: https://doi.org/10.1007/s10722-018-0609-6

Interpretive Summary: The USDA, ARS sweetpotato collection in Griffin, GA, is a valuable resource that is used in the development of new sweetpotato varieties. During 2012-2014, 737 sweetpotato types from the collection were grown out in the field and in pots at Charleston, SC. Appearance is important in the marketability of sweetpotatoes, and color of the skin and flesh are key attributes that contribute to the way a sweetpotato root looks. Therefore, the color of the skin and flesh of these sweetpotato storage roots was evaluated using a colorimeter. Subjective evaluations of the color of the skin and flesh also were made for each sweetpotato type. Skin colors ranged from almost white to dark red, with a few types having purple skin. Flesh colors ranged from white to deep orange, but a few entries had purple or mixed-purple flesh. There were significant relationships between storage root stele color and percent dry matter. Roots with orange flesh had a significantly lower average percent dry matter compared with roots with cream/white flesh. There appears to be wide genetic diversity for both root and vegetative phenotypic characteristics for the United States sweetpotato collection. This study provides comprehensive information for stele and periderm colors that have been lacking for the many types in the collection.

Technical Abstract: USDA, ARS, Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, GA, maintains the U.S. germplasm collection for Ipomoea spp. (Convolvulaceae). During 2012-2014, 737 sweetpotato, Ipomoea batatas (L.) Lam., plant introduction (PI) accessions were acquired as tissue culture plantlets, acclimated to greenhouse conditions, and grown out in the field in replicated plots at the USDA, ARS, U. S. Vegetable Laboratory (USVL), Charleston, SC. Storage roots were harvested from 690 PIs grown in the field and 695 PIs grown in pots, and 659 PIs produced storage roots both in the field and in pots. Several phenotypic leaf, root, and plant characteristics were recorded for each PI accession. Among the characteristics recorded for each PI were color coordinates obtained using a tristimulus colorimeter. Hue angle values (h*) ranged from 8.2° to 88.3° (¯x=54.9°) for the periderm (peel or skin) of field grown storage roots (n=690 PIs) and -9.4° (=350.6°) to 96.2° (¯x=51.3°) for the periderm of pot grown roots (n=695 PIs). Color saturation (chroma, C*) ranged from 13.7 to 35.7 (¯x=24.9) for the periderm of field grown storage roots and 14.9 to 45.5 (¯x=29.3) for the periderm of pot grown roots. Lightness (white black, L*) ranged from 32.6 to 81.7 (¯x=54.6) for the periderm of field grown storage roots and 32.1to 88.2 (¯x=64.0) for the periderm of pot grown roots. Hue angles ranged from -13.1° (=346.9°) to 100.9° (¯x=80.9°) for the stele (flesh) of field grown storage roots (n=672 PIs) and -12.1° to 103.5° (¯x=81.6°) for the stele of pot grown roots (n=676 PIs). Chroma ranged from 12.7 to 65.8 (¯x=37.2) for the stele of field grown storage roots and 8.9 to 65.7 (¯x=34.5) for the stele of pot grown roots. Lightness ranged from 27.8 to 91.1 (¯x=77.7) for the stele of field grown storage roots and 28.2 to 91.9 (¯x=80.4) for the stele of pot grown roots. There were significant relationships between storage root stele color (h*) and percent dry matter and between storage root stele color and dry root density (g/cm3). Roots with orange stele had a significantly lower average percent dry matter (¯x=25.6%) compared with roots with cream/white stele (¯x=30.2%). There appears to be wide genetic diversity for both root and vegetative phenotypic characteristics for the U.S. sweetpotato germplasm collection. This study provides comprehensive information for stele and periderm colors that have been lacking for many PIs.