Fig. 4. Results of the CART analyses of tissue nutrient concentration on incidence of IHN for 4x–2x clones grown in Plymouth, NC, Painter, VA, and Bridgeton, NJ, in 2001 and 2002. At each branch, the tissue nutrient concentration associated with greater resistance to IHN is shown on the left-hand side of the branch and the tissue nutrient concentration associated with greater susceptibility is found on the right-hand side of the branch.