S16 - Session O1 - field testing prunus rootstocks in South Carolina for peach tree short life and armillaria tolerance

Authors: Gregory L. Reighard *, David Ouellette, Ioannis Minas

Seven peach rootstock trials were established in South Carolina between 2003 and 2017 to evaluate rootstock cultivars for resistance to Peach Tree Short Life (e.g., bacterial canker) and Armillaria (i.e., Desarmillaria ) fungal root rot. Twenty-eight rootstocks were planted on Peach Tree Short Life (PTSL) and/or Desarmillaria tabescens replant sites. Species composition of the rootstocks included P. persica , P. americana, P. angustifolia , P. besseyi, P. cerasifera , P. davidiana , P. domestica , P. dulcis , P. insititia , P munsoniana, P. salicina , P. spinosa, P. tomentosa , and P. umbellata. Two rootstock trials were planted at a PTSL replant site on Lakeland sand. After 5 years, Guardian®, 'Mr.S 2/5', Lovell, and P. munsoniana seedling had survival rates of 100, 100, 95 and 70 percent, respectively; whereas trees on 'Adesoto', 'Krymsk® 1', and 'Garnem' were all dead and 'Krymsk® 86', 'S-37' and 'Controller™ 5' had only 20 percent survival. On a fumigated replant site with clay loam soil, 'Rootpac® 40' and 'MP-29' had 10-20 percent tree death from Pseudomonas canker after 4 years, while Guardian® and Lovell had no tree mortality. On an adjacent replant site, 'Tetra' and 'Garnem' had zero survival after 8 years. Guardian® and 'Empyrean® 1' had 60 percent survival, 'Krymsk® 86' had 80 percent and Pisa P.S.A5 and P.S.A6 had 100 percent. Desarmillaria was often associated with the dead trees. Three other orchards were planted on replant sites with a history of PTSL and Desarmillaria root rot . Guardian®, Lovell and 'MP-29' had negligible tree death from PTSL whereas 'Rootpac 20' and 'Rootpac R' had significant tree losses from PTSL. In the oldest orchard, Guardian® and Lovell began dying before year 7 from Desarmillaria tabescens , whereas 'MP-29' had no tree loss from Desarmillaria after 9 years. European interspecific rootstocks had fair to poor survival, in contrast to high survival on Guardian®, Lovell and 'MP-29' rootstocks.