VARIANCE COMPONENTS IN TOBACCO CULTIVAR TRIALS

Abstract

The data from the Comparative Variety Test of flue-cured tobacco cultivars were available from two locations in south-western Ontario for 1964, 1965 and 1966. Eleven cultivars were in common for the combined analysis of variance. Data for 12 characters were utilized.The main effects, years and locations, were not significant for all characters but the effects for genotypes were significant for yield attributes only. The interaction years × locations was significant for 10 of 12 characters. Variance components for genotype × location interaction were small and significant for only two characters. Genotype × year interaction components were significant for four characters. The components for genotype × location × year interaction were significant only for yield, crop index, number of leaves, and petroleum ether extractives. Total theoretical variance, calculated from the components, was utilized to evaluate the adequacy of the number of years, number of locations, and the number of replications in cultivar tests. It is suggested that three locations with four replications for 2 or 3 years would give an adequate evaluation of a breeding line or cultivar performance. From the ecovalence values of the cultivars it was concluded that specific combinations of environmental conditions, rather than the differences among cultivars, were instrumental in producing significant genotype × location × year interactions.