Evaluation of size controlling rootstocks for California peach production

The primary factor limiting the use of size controlling rootstocks in stone fruit production is the lack of availability of suitable rootstocks with a wide range of compatibility among cultivars. From 1986 to 1994 we evaluated 80+ genotypes representing a broad range of genetic backgrounds for their rooting capacity, compatibility with peach (O'Henry) and plum (Santa Rosa), and size controlling characteristics. During 1990 and 1991 we identified 19 potential size controlling rootstock genotypes for peach. In February, 1996 a four-acre experimental rootstock trial was planted at the Kearney Agricultural Center to evaluate the potential of eight of these rootstocks compared to commercially available stocks. This experiment involves ten different rootstocks and two scions. The ten rootstocks are: Alace, Hiawatha, Sapalta (open pollinated seedlings of a Prunus besseyi x P. salicina hybrid), K145-5, K-146-43, K-146-44, P-30-135, (P. salicina x P. Persica hybrids) K-119-50 (P salicina x P. dulcis hybrid), Citation and Nemaguard. The two main scion cultivars are Loadel (an early clingstone processing cultivar) and Flavorcrest (an early fresh market freestone cultivar). Although three of the test rootstocks have exhibited some tree loss due to delayed incompatibility with selected scion cultivars, the results of the other scion/rootstock combinations have been positive. One rootstock (P-30-135) appears very promising with tree size/vigor approximately 70% of Nemaguard and fruit size potential across a range of crop loads greater than or equal to all other tested rootstocks.