Objectives Chinese cabbage is a typical potassium-loving crop, and potassium deficiency seriously affects its yield. Seedling is sensitive to most nutrient deficiencies, so we determined some growth indicators of Chinese cabbage germplasm resources under potassium-efficient, to provide indicators for the breeding and screening of varieties tolerant to low potassium.

Methods Twenty-one Chinese cabbage inbred lines were used in a hydroponic experiment. The Chinese cabbage seedlings were subject to normal (NK, K⁺ 6.0 mmol/L) and low K solution (LK, K⁺ 0.1 mmol/L) for three weeks, then were sampled for determination of root morphology, plant growth, potassium content and potassium accumulation. The principal component analysis and D value cluster analysis of 21 Chinese cabbage varieties were carried out.

Results The root surface area, root volume, root tip number, shoot potassium concentration (SKC), plant potassium concentration (PKC), shoot potassium accumulation (SKA) and plant potassium accumulation (PKA) of 21 Chinese cabbage seedlings were significantly decreased under LK treatment compared with NK treatment. The low potassium tolerance coefficients of the five indexes of SKC, PKC, SKA, root potassium accumulation (RKA) and PKA of all varieties were lower (LPTC<1), while the low potassium tolerance coefficient of root potassium concentration (RKC) was higher (LPTC>1). Among the 21 Chinese cabbage germplasm resources, 3 were low, 3 were moderate low in potassium tolerance; 13 were medium-low and 2 were low potassium sensitive varieties. The low K tolerant cabbage ‘HK42’ did not show significant difference in the shoot potassium transport efficiency under the NK and LK treatment, while the low K sensitive cabbage ‘HK40’ was recorded 58.95% higher root potassium transport efficiency under LK treatment than under NK treatment. Compared with ‘HK42’, the shoot K utilization index and K efficiency ratio of ‘HK40’ were significantly reduced by 74.01% and 81.70%.

Conclusions The root dry weight, shoot potassium accumulation and plant potassium concentration are sensitive indicators to evaluate the low potassium tolerance of Chinese cabbage variety. ‘HK27’, ‘HK42’ and ‘HK54’ have been identified as low potassium tolerant varieties, while ‘HK40’ and ‘HK48’ as low potassium sensitive varieties.