GENETIC AND PHENOTYPIC PATH ANALYSES IN SUGARCANE - ARTIFICIALLY CREATED RELATIONSHIPS

In sugarcane (Saccharum spp.) studies, tonnes per hectare of sugar (THS) is generally computed by multiplying tonnes per hectare of cane (THC) and sugar per tonne of cane (S/T). Because of this multiplication, artificial relationships are created between THS and THC and between THS and S/T, but their effect on the relative importance of THC and S/T in determining THS in path analyses is not known. This study examined the possible effect of the artificially created relationships on the relative importance of THC and S/T in determining THS in genetic and phenotypic path analyses. Four cases, two representing nonindependent measures (artificial relationships) and two representing independent measures of THS and THC, were examined. At the phenotypic level an artificial relationship tended to inflate the relative importance of THC and lower that of S/T, but at the genetic level the artificial relationship did not greatly inflate or decrease the relative importance of THC and S/T. Multiplying THC and S/T to obtain THS reflects spurious associations in the phenotype that can be circumvented by using genetic correlations in path analyses.