Abstract Several methods are available for estimating heritability in disomic species, including parent-off- spring regression, realized heritability, intraclass correla- tions of recombinant inbred lines, and diallel-cross anal- ysis. Estimates were obtained by these various methods for a set of eight bread wheat (Triticum aestivum) lines adapted to the East African highlands, which had been intercrossed and selfed in a half-diallel arrangement to give F 1 , F 2 and F 3 generations, and F 6 recombinant in- bred lines. Significant genetic variation existed among parents and crosses for both grain yield and yellow rust resistance in all generations. Based on the heritability calculated from the analysis of F 6 recombinant inbred lines, analysis of the F 2 diallel crosses was recommended for determining the heritability of both characters in ear- ly segregating generations. The results also suggest that a form of tandem selection may be effective in develop- ing locally adapted germplasm which combines high grain yield with yellow rust resistance. Key words Triticum aestivum · Diallel cross · Parent-offspring regression · Realized heritability · Yellow rust · Yield Introduction Plant breeders work with continuously varying or quanti- tative characters, which are controlled by genes whose in- dividual effects are too small to be detected by conven- tional Mendelian analysis. Hence, the properties and ac- tions of these genes have to be inferred from analyses of the means and variances of appropriate generations or populations (Mather and Jinks 1982; Falconer and Mackay 1996; Kearsey and Pooni 1996; Hill et al. 1998). Information obtained from these analyses can be used to determine in which generation selection should be practi- sed; what the consequences of inbreeding are; what the genetic basis of heterosis is, and whether inbred or hybrid cultivars should be developed? Thus, if a particular char- acter is controlled by recessive genes, selection should be delayed until the generations are more homozygous. If heritability is low then either increased replication is re- quired, or else selection for a correlated character may be practised to increase the chances of identifying superior genotypes (Hill et al. 1999). Dispersion of unidirectional- ly dominant genes among parental lines, leading to better parent heterosis for the character in the F 1 , could be ex- ploited by developing hybrid cultivars. This strategy could also be used during the initial phase of a breeding programme designed to identify those crosses from which a high proportion of superior recombinant inbred lines are expected (Lawrence and Senadhira 1998). Different mating designs have been suggested for cal- culating the heritability of populations derived from in- bred lines in disomic hexaploid wheat (Triticum aes- tivum). Parent-offspring regression and diallel crosses are among the most popular. Alternatively, realized heri- tability and intraclass correlations, calculated from re- combinant inbred lines derived by single-seed descent, may be used. This paper compares these methods of cal- culating the heritability of grain yield and resistance to yellow rust, caused by Puccinia striiformis Westend., in bread wheat germplasm adapted to the East African highlands. Materials and methods Eight wheat lines were selected as parents for this experiment on the basis of their grain yield and resistance to yellow rust at Kalengyere, a high-rust site in the south western highlands of Uganda (Table 1). These eight lines were crossed in a half-diallel Communicated by P.M.A. Tigerstedt W.W. Wagoire · R. Ortiz ( ✉ ) · J. Hill · O. Stølen Department of Agricultural Sciences, The Royal Veterinary and Agricultural University, 40 Thorvaldsensvej, DK-1871 Frederiksberg C, Copenhagen, Denmark Present address: R. Ortiz, ICRISAT, Patancheru 502 324, Andhra Pradesh, India e-mail: rortiz@cgiar.org Fax: +91 40 241239 Theor Appl Genet (1999) 99:1075–1079 © Springer-Verlag 1999 W.W. Wagoire · R. Ortiz · J. Hill · O. Stølen Comparison of methods for calculating the heritability of adult field resistance to yellow rust and grain yield in spring wheat Received: 15 February 1999 / Accepted: 11 March 1999