Collection and Evaluation of Tung Tree (Vernicia fordii) Germplasm Resources in China

Tung tree (Vernicia fordii) is an important woody-oil plant with long cultivation history in China. Its seed has 52% to 64% oil-yields content. Alpha-eleostearic acid, an unusual conjugated trienoic fatty acid (18:3D^{9cis,11trans,13trans}), accounts for 80% (w/w total fatty acids) in tung oil that imparts industrially useful drying qualities to the oil. It can be easily oxidized and forms a unique polymer after being exposed to air. Tung oil is also used as a high-quality raw material in biodiesel production. In order to protect the tung tree resources from disappearing, we have collected more than 200 genetic resources of Vernicia fordii from 16 provinces of China and conserved in 20 hm² land. We investigated the growth and developmental characteristics of these genetic resources as they began to bear fruit, including morphological  characteristics (tree height, diameter at breast height, ground diameter, crown breadth, branch angle, under branch height, and yield), economic fruit traits (fruit size, weight, shape, seed yield, shelling percentage, and seed oil yield) and flower characteristics (color, inflorescence number, and female flower number). According to this work we find some fine genotypes, i.e. maximum number of female flowers per inflorescence (ZNL-F14, 19.5), the heaviest fruit (ZNL -F39, 97.65g), the highest yield (ZNL-F29, 33.59kg), highest seed yield (ZNL-F6, 44.17%), highest shelling percentage (ZNL-F32, 63.90%), highest seed oil yield (ZNL-F52, 65.32%), and maximum oil production per tree (ZNL-F17, 2152.31g). The fatty acid composition was also analyzed using gas chromatography. Some genotypes with beautiful flowers and good tree structure can be used for ornamental tung tree breeding. This work provides resources for cross breeding and selective breeding of tung tree, and provides a foundation for molecular biology research on tung tree.