Figure 6.

Experimental design and PRP orchards layout. A, Google Maps satellite images of the established PRP orchards across the different European sites. B, Experimental design of multisite PRP. A schematic example is provided for the Gimenells location. Accessions (A) and seedlings (S) in each block and subblock were completely randomized. The M1.1 and M1.2 subblocks each include a full copy of the collection (189 accessions, 214 seedlings) plus replicate checks (C) of the accessions cv Big Top, cv Nectaross, and cv Springcrest (five additional trees for each subblock). The M2.1 and M2.2 subblocks include half of the PRP collection and each site has a different half, chosen according to a pairwise design scheme. To this end, accessions (excluding control checks) and seedlings were randomly assigned to eight disjoint subgroups (A1–A4 and S1–S4) of approximately equal size and four of them assigned so that each site shares at least one A or one S group with the other sites. In the example, each M2 subblock at Gimenells is composed of A1 and A2 (46 and 46 accessions, respectively, plus the three checks for a total of 95), S1 and S2 (54 and 54 seedlings, respectively, for a total of 108), and three other additional replicates for each check (nine trees). Gimenells shares the A1 and S1 groups with Mula, S2 with Imola, and A2 with Naoussa.