Evaluation of Chandler Clone Walnut Trees on Various Rootstocks including Its Own Roots - 2004

Reports that “own rooted” Chandler walnuts (Chandler clone) out preformed grafted trees stimulated the creation of this replicated trial to investigate the performance of Chandler clone trees, Chandler clone grafted to Chandler clone rootstock, Chandler clone grafted to three selections of paradox rootstock and Chandler clone grafted to a vigorous English rootstock. Rootstock trees were planted in March 1999 at the California State University Farm in Chico. Tops were grafted with graft wood collected from mature Chandler clone trees in the spring of 2000. Initial survival, yield and trunk cross sectional area (TCSA) data collection began in 2001. Catkin abundance, tree yield, yield efficiency, and TCSA data was collected in 2004 and reported. OBJECTIVES The objectives of this trial are to validate or refute the following hypothesis: 1. Graft union has a limiting effect on tree growth and productivity. 2. Chandler is a superior English rootstock. 3. Clonal paradox has less variation than paradox seedling rootstocks. 4. Chandler clone trees are superior to Chandler on paradox. PROCEDURES The following six treatments are being evaluated: 1. Chandler clone via tissue culture. 2. Chandler clone via tissue culture grafted to Chandler clone. 3. English (Waterloo) rootstock grafted to Chandler clone. 4. Common paradox rootstock grafted to Chandler clone. 5. “Trinta” paradox rootstock grafted to Chandler clone. 6. Clonal paradox (PX1), grafted to Chandler clone. Small (3/8” diameter) rootstocks for these six treatments were planted on March 19, 1999 in a randomized block design with six replicates made up of two trees per replicate. Top working (grafting) took place in the spring of 2000. Graft wood was collected from mature Chandler clone trees. Initial tree survival data was collected in 2000. 2004 catkin abundance, tree growth expressed as trunk cross sectional area (TCSA), nut quality data, and yield data was collected. Yield efficiency was calculated and is presented as well. RESULTS Initial tree survival in 2000: Treatment 1 = 100 % Treatment 4 = 58 % Treatment 2 = 100 % Treatment 5 = 75 % Treatment 3 = 92 % Treatment 6 = 100 % In 2003 one tree from treatment five died making the % survival 67%. Presence of crown gall: Treatments four (common paradox) and six (clonal paradox-PX1) each had one visible crown gall. Catkin abundance: Using a rating system of: 1 = no catkins; 2 = low number of catkins; 3 = moderate number of catkins; 4 = high catkin abundance and 5 = very high catkin abundance observations were that Chandler clone trees had an average catkin abundance rating of 1.1 while all other treatments averaged between 2.4 and 3.0. The catkin abundance on the Chandler clone tree was significantly less than that of all other treatments. (Graph 1).