Morphologic Variation in the USDA/ARS Rhubarb Germplasm Collection

Authors: Pantoja, Alberto; Kuhl, Joseph

Submitted to: Plant Genetic Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2009
Publication Date: 7/17/2009
Citation: Pantoja, A., Kuhl, J.C. 2009. Morphologic Variation in the USDA/ARS Rhubarb Germplasm Collection. Plant Genetic Resources. Available: http://journals.cambridge.org/action/displayAbstract?aid=5946564.

Interpretive Summary: Rhubarb includes approximately 60 species in the genus Rheum, most occur in mountainous and desert regions of central and northern Asia. Rhubarb has been used for medicinal purposes in China for thousands of years. In the middle of the 17th century, rhubarb species began to be grown in Europe for medical uses. In the early 1700s, it was discovered that some rhubarb plants started from seed had edible stalks. Culinary rhubarb, R. rhabarbarum L., was primarily identified by selecting seedlings that exhibited desirable horticultural characters from open pollinated seeds. It is believed that R. rhaponticum, R. undulatum, and R. palmatum were involved in early hybridizations, although pedigrees are mostly absent from these early open pollinations. The true species composition of culinary rhubarb remains unclear today. Over the years many cultivars have been identified with 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 a multitude of phenotypes. This study reports the results of morphological data collected during two seasons for 36 rhubarb cultivars and two rhubarb species from Palmer, Alaska (N61.57°, W149.26°). Traits of interest are discussed and future modifications suggested. Two years of morphological data are reported here, with a focus on horticultural characters. Modifications are suggested to improve reproducibility between years and reliably separate cultivars based on morphological characters.

Technical Abstract: Rhubarb includes approximately sixty 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 a multitude of phenotypes. Two years of morphological data are reported here, with a focus on horticultural characters. Results suggest that data from the two years should not be combined. Modifications are suggested to improve reproducibility between years and reliably separate cultivars based on morphological characters.