The Citron (Citrus medica L.) in China

Abstract

Citron (Citrus medica L.) is the type species of the genus Citrus, one of the primary species of cultivated citrus, and a parent or ancestor of the commercially important acid citrus fruits. Southwestern China is a crucial center of origin and diversity for citron. The diversity of this species in China is extensive, but poorly documented until recently. Prized for its fragrance, citron played an important role in Chinese art and culture. Today, citron is grown in most of the warmer citrus‐producing areas of China, and is used in Chinese traditional medicine, ornamental pot culture, and for human consumption as both fresh and processed products. In Chinese traditional medicine, dried citron is used as a tonic, to regulate Qi, the life force. Citrons are classified by fruit shape as either common (nonfingered) or fingered. In most of China, fingered citrons predominate because they are more suited to cultivation for medicinal and ornamental uses. Typically, common citrons grown in China have locules in which juice vesicles are absent, or are very scanty and rudimentary. ‘Ning’er Giant’, typically weighing 3–5 kg, sometimes reaching 8–10 kg, may be the world’s largest citrus cultivar. Fingered citron trees vary in stature, cold hardiness, flower color, and other significant horticultural characteristics; the fruits vary in size, shape, number and thickness of fingers, proportion of fruits that are open or closed, and the point on the fruit at which the carpels become distinct. The distinctive forms of many named cultivars reflect different genotypes. There also exist in China genotypes that are intermediate in morphology between common and fingered citron. Putatively “wild” citron trees producing small fruits grow in forests, in semi‐wild margins between natural and cultivated areas, and in private gardens in the subtropical forests of western and southern Yunnan. Scientists in China and elsewhere have paid increasing attention to citron germplasm resources during recent years.

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