Chromosome control implied by the physiological responses of root in wheat substitution lines seedlings under phosphorus deficiency stress

Objectives Studying on the physiological responses of seedling roots of wheat substitution lines to phosphorus deficiency stress and chromosomal localization of genes controlling root properties will provide theoretical support for screening cultivars tolerant to low phosphorus.

Methods The seeds of mother line‘Chinese Spring (CS)’and father line “Synthetic 6x” as well as the substitute seeds of CS with Synthetic 6x were placed in cultural dishes for germination for 5 days. Then healthy and uniform seedlings were chosen and removed off endosperms, then cultured in Hoagland solution (pH 6.0) until the third leaf sprouting. The seedlings were grown in P₂O₅ 2 mmol/L (normal control) or low P₂O₅ stress (P₂O₅ 20 μmol/L) until the fifth leaf start to sprouting. The root-shoot ratio, root activity, root Apase and RNase activity and chromosome control were observed using wheat substitution lines seedling under different phosphorus treatments.

Results The root-shoot ratio, Apase activity and RNase activity increased, and root activity reduced under phosphorus deficiency stress. The root-shoot ratio and relative root-shoot ratio of 4A, 4B, 6B, 1D, 2D and 7D substitution lines were significantly or very significantly higher than those of the female parent Chinese Spring, root activity and relative root activity of 1A, 2A, 3A, 5A, 3B, 7B, 1D, 2D, 3D, 5D and 7D substitution lines were significantly or very significantly higher than those of Chinese Spring, Apase activity and relative APase activity of 4A, 1D, 4D were also significantly or very significantly higher than those of Chinese Spring. RNase activity and relative RNase activity of 2A, 6B, 4D were also significantly or very significantly higher than those of Chinese Spring.

Conclusions For Synthetic 6x under phosphorus deficiency stress, there might exist genes on chromosome 4A, 4B, 6B, 1D, 2D and 7D to induce high root to shoot ratio, some genes on chromosome 1A, 2A, 3A, 5A, 3B, 7B, 1D, 2D, 3D, 5D and 7D to promote root activity, some genes on chromosome 4A, 1D and 4D in Synthetic 6x to regulate Apase activity, and some genes on chromosome 2A, 6B and 4D to regulate RNase activity. Generally, there might exist some key genes of regulating root characteristics on the forth chromosome (4A, 4B, 4D) of Synthetic 6x.