5 - Welsh onion: Allium fistulosum L.

Abstract

Publisher Summary The large and widespread genus Allium (Liliaceae) contains a small number of economically important species. One of these, the Welsh onion, Allium fistulosum L., is widely cultivated in the Far East, particularly in Japan, China, and Korea. The center of origin for the species is generally regarded as being central and northwestern China. The Welsh onion, which is a perennial, herbaceous plant, usually grown as an annual for its edible tops, long leaf bases, or young shoots, has been in cultivation for many centuries; references to it can be found in Chinese literature dating from the third century BC. World production of this vegetable is centered on Japan, Korea, China, and Taiwan, where it ranks in importance among the top ten vegetable crops. The basic chromosome number of Allium fistulosum is 8. This chapter discusses the cytology of the Welsh onion. The Welsh onion possesses resistance to several diseases that affect common onions as well, and it also exhibits broad adaptability to a wide range of climatic conditions, winter-hardiness, and early flowering. In the case of Allium fistulosum, where the wild progenitor is not known, the cultivated germplasm forms the primary gene pool of the crop. Traditionally, most farmers growing Welsh onion have raised their own seed and this clearly indicates the potential for conserving genetic variation in the form of landrace material of the species. Breeding work has only recently been carried out to improve cultivar performance and uniformity. At present, there are over 120 registered cultivars of Welsh onion in Japan, only some of which have been developed as F1 hybrids using male sterility. The chapter discusses breeding of onion for disease resistance and quality. As the Welsh onion—in relative terms—has not been the focus of large-scale varietal improvement over a long period, considerable scope still exists for further improvement.