Abstract
There are several known sources of thornlessness for blackberries. Some of these have been used as parents and their genetics are quite well understood; others remain relatively unknown. The source and nature of thornlessness in blackberry has been reviewed by George Darrow (1937), Jack Hull (1968), and Derek Jennings (1986). In this paper we review the literature on thornlessness, discuss the status of the thornless parents discussed in these older reviews, and we also discuss more recent literature related to thornlessness, new sources of thornlessness, and the genetic basis of thornlessness.