MUTATION BREEDING FOR IMPROVED INTERNAL QUALITY AND APPEARANCE IN RUSSET-BURBANK

Mutation breeding was investigated as a method to improve important qu ality traits in the cultivar Russet Burbank. Two thousand excised eyes were irradiated with a gamma-ray dose of 35 Gy. The irradiated eye pi eces were planted directly to the field and approximately three tubers from each of resulting plants were harvested and, constituted the ini tial 6000 clone selection population. The M(1)V(1) tubers and subseque nt clonal progeny were subjected to six generations of evaluation and selection. Selection criteria included appearance, resistance to black spot bruise, french fry color following storage at 4 C, and specific g ravity. At the end of six selection cycles, five mutants remained from the original population of approximately 6000. These included two mut ants selected for improved appearance (RBM161 and RBM366), one for res istance to blackspot bruise (RBM166), one for french fry color (RBM13) , and one for specific gravity (RBM170). An analysis of variance over three years showed that the three mutants selected for internal qualit y traits (RBM13, RBM166, and RBM170) produced lower yields in comparis on with two Russet Burbank control clones. RBM161 was selected for its heavier, more uniform russet skin, and appeared to be similar to the mother clone for important agronomic and quality traits. RBM366 was se lected for improved appearance, typified by higher breeders preference scores and a lower percentage of tubers exhibiting external defects. It also produced higher total and U.S. No. 1 yields than the controls.