Morphologic variation in the USDA/ARS rhubarb germplasm collection

Rhubarb includes approximately 60 species in the genus Rheum It has been utilized for thousands of years for medicinal purposes, but only recently identified for its culinary use In the mid 1700s. edible petioles were discovered on seedlings from rhubarb species Hundreds of cultivars have since been identified for a wide range of uses from tarts to wine Unfortunately, propagation by seed and irregular naming has resulted in a plethora of similarly named cultivars and multitude of phenotypes Fifteen morphological characters were evaluated to differentiate rhubarb cultivars in the USDA, ARS Rheum collection in Palmer, Alaska Two years of morphological data, focusing on horticultural characteristics indicated variation between the years To improve cultivar resolution, the results suggest using 1 year's data instead of combining data horn different years The mean degrees Brix observed was 3 8, with a range from 2 2 to 6 1 Flesh colour and basal skin colour were poorly correlated (R-2 = 0 462), overall skin colour was more red at the base than in the middle of the petiole Rhubarb character categories, in particular petiole number and petiole base thickness, need to be modified to better anticipate the range of expected values, and thereby contribute improved reproducibility and reliability to separate cultivars based on morphological characters