LOW CORRELATION BETWEEN GENOMIC AND MORPHOLOGICAL INTROGRESSION ESTIMATES IN A WALNUT BACKCROSS

A first backcross population of walnuts {[Juglans hindsii (Jeps.) Jeps . x Juglans regia L.] xJ. regia} was used to evaluate the correlation between morphological (statistical) and genetic distance during introg ression. Five traits based on leaf morphology were identified to quant itate the morphology of the parental species, their Fl hybrids, and th e backcrosses to each parent. These traits were used to evaluate the m orphological similarity of first backcrosses to J. regia using Mahalan obis' distance. The amount of genomic introgression of each backcross was estimated using 59 randomly amplified polymorphic DNA (RAPD) and 4 1 restriction fragment-length polymorphism (RFLP) genetic markers that identify polymorphisms between J. regia and J. hindsii. A smaller sca ffold set of markers was also identified using published linkage data. The correlation between the measures of morphological and genomic int rogression for the first backcrosses was low (0.23) but significant. T he results suggest that selection based on morphology during backcross ing will not be an effective way to recover recurrent parent genome.