Brazilian Journal of Genetics
versión impresa ISSN 0100-8455
versión On-line ISSN 1678-4502
CHAVES, Lázaro J y MIRANDA FILHO, José B. de. Predicting variety composite means without diallel crossing. Braz. J. Genet. [online]. 1997, vol.20, n.3, pp.-. ISSN 0100-8455. http://dx.doi.org/10.1590/S0100-84551997000300023.
Prediction of variety composite means was shown to be feasible without diallel crossing the parental varieties. Thus, the predicted mean for a quantitative trait of a composite is given by: Yk = a1 SVj + a2STj + a3 - a4, with coefficients a1 = (n - 2k)/k2(n - 2); a2 = 2n(k - 1)/k2(n - 2); a3 = n(k - 1)/k(n - 1)(n - 2); and a4 = n2(k - 1)/k(n - 1)(n - 2); summation is for j = 1 to k, where k is the size of the composite (number of parental varieties of a particular composite) and n is the total number of parent varieties. Vj is the mean of varieties and Tj is the mean of topcrosses (pool of varieties as tester), and and are the respective average values in the whole set. Yield data from a 7 x 7 variety diallel cross were used for the variety means and for the "simulated" topcross means to illustrate the proposed procedure. The proposed prediction procedure was as effective as the prediction based on Yk = - ( -)/k, where and refer to the mean of hybrids (F1) and parental varieties, respectively, in a variety diallel cross. It was also shown in the analysis of variance that the total sum of squares due to treatments (varieties and topcrosses) can be orthogonally partitioned following the reduced model Yjj = m + ½(vj + vj) + + hj+ hj, thus making possible an F test for varieties, average heterosis and variety heterosis. Least square estimates of these effects are also given