“…The history of genetic investigation of GPC has completely repeated that of other quantitative characters. Depending on the material examined, the method of trait assessment, and the procedure of treatment of the results, different conclusions were made: the number of genes were estimated as one or many [8], while the heritability coefficient varied in the range from 0.25 to 0.70 [8][9][10][11][12]. In most studies, the character was considered polygenic, although some authors argues that it was controlled by a small number of major genes and several modifier genes.…”