Climatic and genetic effects in seasonal measurements of colour in Corriedale wool

Abstract Wool colour is an important quality trait indicating dyeing potential, and it is described by two components: yellowness and brightness. The aims of this research were to: a) estimate the effect of climatic variables on wool yellowness and brightness; b) know if wool colour was genetically the same trait or it is expressed differently along time. Data from ewes progeny (n = 1371) of two experimental flocks were used. Mid-side and back wool samples were taken in summer, autumn, winter, and spring, to determine yellowness and brightness. Models considered the fixed effects of sex, litter size, experimental station, staple length, average maximum temperature, accumulated rainfall and average relative humidity, and the animal as a random genetic effect. Differences between sampling areas were estimated by the simple use of Test t (Student) for differences between means. A yellowness value of 1.77 ± 1.77 units was found in spring sampling (complete staple length), with great variability between animals; brightness was 63.58 ± 3.63. The lowest yellowness values ​​were obtained in the winter sampling; the yellowness value recorded in the back area was significantly higher than that obtained in mid-side (P This study demonstrates that yellowness and brightness are associated with climatic effects. Wool colour traits are heritable and the moderate genetic associations among seasonal samplings suggest that they were not the same trait along time. Further investigation should be conducted to study possible interactions among climatic variables, as well as seasonal genetic variation in yellowness and brightness. Genetic correlations with other economically important traits is another area for future studies.