a1 Department of Agriculture, Animal Research Branch, Box 1671 GPO, Adelaide 5001, Australia
a2 University of Adelaide, Department of Physical and Inorganic Chemistry, Box 498 GPO, Adelaide 5001, Australia
Wool samples were collected from two groups of Merino sheep, both of which contained animals that were either heterozygous (Ww) or homozygous (WW) for white fleece. Group 1 were sampled in summer and group 2 in winter. These samples were scoured and measured for electron spin resonance initially (ESR1), following irradiation by ultraviolet light (ESR2) and then after wetting and drying the sample (ESR3).
There was no significant difference between WW and Ww sheep in each group for any of the ESR measurements (P > 0·05). However, for ESR1 there was a difference between management groups (group 1> group 2; P < 0·05). The ESR3 on ESR1 values were plotted separately for WW and Ww genotypes. The plotted ESR3 on ESR1 values in both groups showed no differentation into distinct genotype clusters. Nevertheless, for group 2 there was a slight similarity to the cross-like pattern of genotypes reported in an earlier description of this technique and the regression coefficients of ESR3 on ESR1 for WW sheep (b = −0·09 (s.e. 0·28)) differed significantly from those of Ww sheep (b = 1·31 (s.e. 0·52)) (P < 0·05).
It appears that the previously published method for differentiating between sheep that are either heterozygous or homozygous for white fleece was ineffective in this case.
(Received March 10 1987)
(Accepted February 23 1988)