Blackberry Breeding In the Midwest

There have been between 450 and 500 blackberry cultivars named thus far, including wild and developed genotypes, according to a recent review. Since 1985, over 60 cultivars have been named. Blackberry cultivars for the region of the U.S. east of the Rocky Mountains are distinctly different than those grown in the western states. The western cultivars tend to lack winter hardiness for much of the East, are trailing, and can suffer substantial disease pressure. They are viewed by many to be the highest quality however, particularly in flavor. In general there exists a substantial genetic divide between eastern and western cultivars. Midwestern cultivars have been developed based on several early wild selections that were named, including ‘Eldorado’ (Ohio, 1880), ‘Lawton’ (date unknown, New York), and ‘Brewer’ (New Jersey, 1920). Subsequent breeding resulted in cultivars such as ‘Hedrick’, ‘Darrow’, and ‘Brazos’. The introgression of thornlessness from the English cultivar ‘Merton Thornless’ by the USDA-ARS was a great advance, and led to a series of thornless, hardy cultivars for the Midwest with ‘Chester Thornless’ and ‘Triple Crown’  being the most popular currently.  Other breeding developments have contributed over the years including ‘Illini Hardy’, and several cultivars from the University of Arkansas. However, the Arkansas cultivars have not been hardy throughout the Midwest and are not reliably adapted to more northern areas of the region.  The major limitation to blackberry production in the Midwest is winter hardiness, and breeding for this along with other traits such as fruit quality, thornlessness, and plant productivity and health are the top priorities. Primocane-fruiting has recently surfaced as an approach to address winter hardiness, allowing fruit to be borne on current-season canes that do not have to be overwintered. Most breeding activity has ceased in the Midwest, although the University of Arkansas program is very active in flori- and primocane-fruiting breeding and it is hoped that products from this program will be useful in all areas of the region.