ENHANCED HERITABILITIES AND BEST LINEAR UNBIASED PREDICTORS THROUGH APPROPRIATE BLOCKING OF PROGENY TRIALS

Progeny test experiments with Ii-year-old lodgepole pine (Pinus contor ta Dougl. ex Loud. var. latifolia Engelm.) half-sibs on northern Swedi sh forest land were repeatedly evaluated with varied subdivision into blocks in order to eliminate environmental variation. The examined sin gle-tree plot experiments that were studied were each planted with 160 0 trees from about 140 families at 1 x 2.2 m spacing. The analyses wer e carried out using restricted maximum likelihood (REML) variance esti mation and best linear unbiased predictors (BLUP) evaluation. The resu lts suggest that subdivision into 10 blocks containing approximately 1 60 trees each may be optimal. With as many as 80 blocks containing onl y 20 trees each, some genetic information was clearly confounded and l ost together with the environmental variation which was eliminated. It is recommended that optimal blocking of single-tree plot experiments be attempted at the time of analysis, regardless of whether the experi ment originally was designed and established with blocks.