Physiological Responses of Seedlings of Different Apple Rootstocks to Salt-Alkali Complex Stress

【Objective】 The salt-alkali tolerance of different apple rootstocks was comprehensively evaluated, and apple rootstocks suitable for cultivation in saline-alkali soil in southern Xinjiang were selected. 【Method】 Using 7 four-year-old apple rootstocks of M. hupehensis (Pamp.) Rehder, M. xiaojinensis Cheng et Jiang, M. robusta, M. hupehensis, M. sieversii Roem, M. Chaenomeles, and M. baccata Borkh as the test materials. NaCl, Na₂SO₄, NaHCO₃, Na₂CO₃ were mixed in the proportion of 1∶9∶9∶1, and 1/2 Hoagland nutrient solution was irrigated in a pot, simulating the mixed saline-alkaline stress of 0, 15, 30, 45 and 60 mmol/L. The chlorophyll content, relative conductivity, and proline content of the leaves of seven apple rootstocks under mixed salt-alkali stress were measured. The membership function method was used to comprehensively evaluate the salt tolerance of each rootstock. 【Results】 With the increase of stress intensity, the chlorophyll content of each rootstock decreased, the relative conductivity and proline content showed an overall upward trend, the total soluble sugar content first increased and then decreased, the soluble protein content showed two trends of "increase decrease increase". 【Conclusion】 The salt-tolerant ability of the seven tested apple rootstocks in order from strong to weak was M. robusta > M. sieversii Roem > M. hupehensis > M. xiaojinensis Cheng et Jiang > M. baccata Borkh > M. Chaenomeles > M. hupehensis (Pamp.) Rehder.