Wheat cultivars should have long primary roots to allow good crop establishment, considering the short crop establishment season (April) in the State of São Paulo, Brazil, where the occurrence of water stress is frequent. This paper demonstrates the control and type of inheritance of the primary root growth trait. Crosses were made between genotypes, BH-1146 and KAUZ "S"/IAC-24 M4 with strong and reduced primary root growth, respectively. F2 and F3 generation seeds from these crosses and F2 generation seeds from the backcrosses of both parents were also obtained. Seedlings from these genotypes plus the parentals were evaluated in relation to primary root growth in complete nutrient solutions containing 3.875 mg L-1 phosphorus, at pH 4.0 and a temperature of 25 ± 1°C for 10 days. Control of the primary root growth trait was demonstrated to have quantitative inheritance. The degrees of dominance showed that the genes for strong root growth had a partially recessive behavior. Heterosis and heterobeltiosis values were negative. The estimated broad-sense heritability for root growth indicated that a great part of the observed variation was of genetic origin. The narrow-sense heritability indicated that a great part of the total genetic variability in relation to the trait under consideration is due to a small number of genes. Considering the estimated coefficient of determination, selection for strong root growth would be effective even when made in the early segregant generations after the cross.
root growth; nutrient solution; recessive genes
