COMPARISON OF TRAIT ASSOCIATIONS IN ADAPTED-X EXOTIC MATINGS OF SORGHUM DEVELOPED BY 2 INTROGRESSION METHODS

The association among six traits in the F-2 lines derived from adapted x exotic backcrosses of sorghum developed via two introgression metho ds was studied using principal component analysis. The first principal component defined a hybrid index in matings of the wild accession ('1 2-26') but not in matings of the cultivated sorghum genotypes ('Segeol ane' and 'SC408'), no matter which adapted parent was used. This compo nent accounted for 27-42% of the total variation in each mating. The ' recombination spindle' was wide in all matings of CK60 and KP9B, which indicated that the relationships among traits were not strong enough to restrict recombination among the parental characters. The index sco res of both CK60 and KP9B matings showed clear differentiation of the backcross generations only when the exotic parent was the undomesticat ed wild accession ('12-26'). None of the distributions of the first pr incipal component scores in any backcross population was bimodal. The frequency of recombinant genotypes derived from a mating was determine d by the level of domestication and adaptation of the exotic parent an d the genetic background of the adapted parent. Backcrossing to a popu lation (KP9B) was found to be superior to backcrossing to an inbred li ne (CK60) to produce lines with an improved adapted phenotype.