Rooting traits of peanut genotypes differing in drought tolerance under drought stress

The effects of two water regimes (well-watered condition or drought stress) on root length,root surface area and root volume were tested on two peanut genotypes (the drought-resistantvariety HuaYu 22 (HY22) and the drought-sensitive variety HuaYu 23 (HY23)), measured 101days after sowing. The roots were sampled from the upper (0–40 cm) and deeper (40–100 cm)soil layers. Root diameter was measured to the nearest 0.5 mm in describing its distribution.Total dry weight and pod yield were measured at harvest. The drought tolerance index of podyield and the harvest index in HY22 were higher than those in HY23. The total root lengthdensity (RLD), total root surface area and volume were significantly higher for HY22 thanHY23. The RLD in the deeper soil layer was lower for HY23 than HY22. Under drought stress,the percent RLD in the deeper layers increased in both genotypes. Compared to well-wateredcondition, the total root surface area and root volume in the upper soil layer were lower underdrought stress and root traits in deeper soil layers were higher. Drought stress had no impact onvery fine roots (diameter < 0.5 mm) of HY22 in the deeper soil layer but lowered their share inHY23 markedly. The RLD and root surface area in the deeper soil layer were related to the podyield of peanut. This finding could be useful in growing peanut under drought conditions.