Additional index words. Rubus, fruit breeding, spineless 'Marion' is currently the most important blackberry (Rubus L. subgenus Rubus) cultivar in the world as it is the predominant cultivar grown for the processed-fruit market (Finn et al., 1997). While 'Marion' produces fruit of outstanding quality for processing, the plants are thorny (botanically termed spiny). When 'Marion' is machine harvested, thorns can end up in the product (Strik and Buller, 2002), which can lead to a poor product, and, more signifi cantly, in an economic sense, lawsuits. As a result, a primary priority for the breeding program has been the development of cultivars that are thornless, machine harvestable, and retain the excellent processing characteristics of 'Marion'. Three thornless blackberry cultivars with these qualities are being released simultaneously: 'Black Diamond', 'Black Pearl' (Finn et al., 2005a), and 'Nightfall' (Finn et al., 2005b). 'Black Diamond' is a thornless trailing blackberry from the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS) breeding program in Corvallis, Ore., released in cooperation with the Oregon State University Agricultural Experiment Station and the Washington State University Agricultural Research Center (Fig. 1). 'Black Diamond' is high-yield-N-71's parentage is much more straightforward but nonetheless complex as it is a cross between 'Aurora', a trailing cultivar whose ploidy is 8x +2, and 'Comanche' a 4x erect blackberry from the University of Arkansas. 'Black Diamond' is the result of tremendous cooperation amongst breeders who have shared their germplasm.