2014 ASHS Annual Conference

Eighteen Prunus rootstocks budded with ‘Redhaven’ peach were planted near Clemson, SC in Jan. 2009.  The rootstocks tested included 6 interspecific Prunus hybrids and seedlings of 3 Prunus species.  After five growing seasons, significant differences among rootstocks were found for survival, root suckers, growth, bloom date, fruit maturity date, fruit size, cumulative yield, and yield efficiency.  Tree survival was high (100%) in all but 4 rootstocks.  ‘Imperial California’ had the lowest overall survival (38%) followed by P. americana seedling and ‘Controller™ 5’ (both 75%).  Rootstock suckering was excessive on Prunus americana seedlings and Krymsk®1.  Tree TCSAs were largest on ‘Mirobac’ (aka ‘Replantpac’) followed by Guardian®, ‘Viking’, ‘Bright’s Hybrid #5’ and ‘Atlas’, whereas TCSAs of trees on Krymsk®1 and P. americana were the most dwarfing.  ‘Controller™ 5’ and ‘Empyrean® 3’ (aka ‘Tetra’) were semi-dwarfing, and ‘Fortuna’ and ‘Imperial California’ had compatibility and disease issues, respectively.  The earliest bloom by 1-1.5 d occurred on ‘Krymsk® 86’ and KV010127 rootstocks. Trees on P. americana and ‘Fortuna’ bloomed 1-3.5 d later than the average in 2011, 2012 and 2013.  Fruit maturity dates varied by 10 d if ‘Imperial California’ (5 d early) and ‘Fortuna’ (5 d late) were included though both were weak rootstocks for peach.  Otherwise, ‘Redhaven’ fruit from ‘Empyrean® 3’ and ‘Krymsk® 1’ trees ripened 3 to 3.5 d earlier than Lovell, the standard.  Fruit size was largest on ‘Imperial California’ trees but was due to very low crop load. ‘Fortuna’ produced the smallest fruit.  Cumulative yields were highest on the vigorous peach and peach hybrid rootstocks.  Rootstocks with the highest yield efficiency were semi-dwarfing such as ‘Krymsk® 1’, ‘Controller™ 5’, ‘7’ & ‘8’, P. americana and ‘Empyrean® 2’ (aka ‘Penta’).