Field Performance and Phenotypic Stability of Tissue Culture-propagated Thornless Blackberries1

<jats:title>Abstract</jats:title> <jats:p>Comparative field performance of thornless blackberry plants produced by tissue-culture (TC) and standard (ST) methods (tip layers or stem cuttings) was studied to determine any effect of TC propagation on clonal phenotypic stability. In general, TC plants performed as well as, and were phenotypically similar to, ST plants. Some differences in leaf size and pattern were observed; however, the differences were related to the increased vigor of TC plants of these cultivars. Total growth of TC and ST plants of ‘Black Satin’, ‘Hull Thornless’, ‘Thornfree’, and SI-US 68-6-17 was similar. ST plants of ‘Dirksen Thornless’ and ‘Smoothstem’ failed to grow as rapidly as TC plants of these cultivars or ST plants of the other cultivars, resulting in significantly reduced 2nd-year yields. First-year growth of all TC plants was more uniform than corresponding ST plants. On the average, fruit size was smaller on TC plants; however, this was true in both years only for ‘Black Satin’. The response varied for other cultivars with TC plants of ‘Dirksen Thornless’ actually having larger fruits in one year. No consistent differences in bloom date or median harvest date due to propagation method were observed. No variant plants were observed in the field; however, one sectorial leaf chlorotic variant was observed after TC propagation but prior to field planting.</jats:p>