Phenotypic analysis of leaf colours from the USDA, ARS sweetpotato (Ipomoea batatas) germplasm collection

Authors: JACKSON, D. MICHAEL - Collaborator; HARRISON, JR., H - Retired ARS Employee; Jarret, Robert - Bob; Wadl, Phillip

Submitted to: Plant Genetic Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/8/2019
Publication Date: 3/1/2019
Citation: Jackson, D., Harrison, H.F., Jarret, R.L., Wadl, P.A. 2019. Phenotypic analysis of leaf colours from the USDA, ARS sweetpotato (Ipomoea batatas) germplasm collection. Plant Genetic Resources. https://doi.org/10.1017/S1479262119000042.
DOI: https://doi.org/10.1017/S1479262119000042

Interpretive Summary: The USDA, ARS sweetpotato collection in Griffin, Georgia 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 by ARS scientists at Charleston, South Carolilna. Leaf color of 731 of these sweetpotato accessions were measured using a colorimeter. Most (726) of the accessions had medium to dark green leaves. Three accessions had yellowish leaves, and two accessions had purple leaves. Numerical averages for hue angle, chroma, and lightness were calculated for the upper and lower leaf surface of each accession. There appears to be wide genetic diversity for both root and vegetative phenotypic characteristics within the USDA sweetpotato germplasm collection. This study provides comprehensive information for leaf colors that have been lacking for many accessions in the collection.

Technical Abstract: The United States Department of Agriculture (USDA), Agricultural Research Service (ARS), Plant Genetic Resources Conservation Unit (PGRCU) in Griffin, Georgia maintains the United States germplasm collection for Ipomoea spp. (Convolvulaceae). Color characteristics were evaluated for the mature leaves of 731 of the 737 sweetpotato, Ipomoea batatas (L.) Lam., plant introduction (PI) accessions that 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. Color coordinates of the abaxial and adaxial leaf surfaces were measured with a tristimulus colorimeter, and data were recorded using the CIE 1976 L*a*b* and CIE L*C*h* color spaces. Subjective color ratings and colorimeter data for mature (fully expanded), early season leaves from field grown plants showed that most accessions (726 of 731 PIs) had dark to medium green leaves, but two PIs had totally purple leaves, and three PIs had yellow or yellow green (chartreuse) leaves. For the 726 PIs with primarily green leaves (some had purple leaf veins), the values for the red-green coordinate (a*) for mature, field grown leaves averaged -12.4 for the adaxial and -10.4 for the abaxial leaf surface, and values for the blue-yellow coordinate (b*) averaged 17.2 for the adaxial and 17.3 for the abaxial leaf surface. Hue (h*) for green leaves averaged 120.9° for the adaxial and 126.2° for the abaxial leaf surface. Color saturation (Chroma, C*) for averaged 21.3 for the adaxial and 20.2 for the abaxial leaf surface of green leaves. Lightness (L*) for averaged 35.4 for the adaxial and 47.2 for the abaxial leaf surface. Late in the season, over one half (53.9%) of the 731 PIs showed some level of purple leaf pigmentation. Purple leaves were collected and color coordinates were recorded for 118 PIs grown in the field. For purple leaves, h* values were scattered over a large range from 1.9° to 118.7°.