Abstract: Aims Saline alkali land is an important reality and potential agricultural resource to solve the shortage of arable land in China. Efficient utilization of saline alkali land resources to develop peanut planting in such environments and achieve high and stable yield has become an urgent demand for ensuring peanut production. Under saline alkali stress habitat, arbuscular mycorrhizal fungi (AMF) can effectively develop potential productivity of host plants and improve their salt resistance and tolerance. Although it has been demonstrated that AMF enhanced peanut salt tolerance under salt stress, however, there have been limited reports on the effects of AMF on the growth and development of salt-tolerant and salt-sensitive peanut. This study was guided by the significant demand for soil improvement in saline alkali land by investigating the response mechanisms of peanut growth and rhizosphere soil environment to AMF under saline-alkali conditions, aiming to provide theoretical basis and technical support for AMF application in peanut production in saline alkali soils. Methods The experiment used salt-tolerant cultivar HY25 and salt-sensitive cultivar HY22 as experimental materials, with AMF seed coating treatment applied under saline alkali and normal soil conditions. Important findings Under two soil conditions, salt-tolerant and salt-sensitive peanut cultivars demonstrated differential response mechanisms to AMF inoculation. Under both soil environments, AMF improved the agronomic characteristics in HY25, optimized photosynthetic parameters, and significantly increased pod yield and its component components. While AMF exhibited partial inhibitory effects on agronomic traits in HY22 in normal soil, it notably improved leaf photosynthetic performance and elevated both pod yield and quality. Significant differences were found in the response of root growth of two cultivars to AMF including: 1) In normal soil, the promoting effect of AMF on the growth of HY25 root system initiated during the flowering-pegging stage and continued to until maturation stage. Under saline-alkaline soil, AMF significantly increased total root length, root surface area, and root volume in HY25 at pod-setting stage. 2) Salt-sensitive cultivar HY22 exhibited greater sensitive to AMF inoculation. Under both normal and saline-alkali soils, AMF demonstrated inhibitory effects on root growth in HY22 during flowering-pegging and/or pod-setting stages, with significantly stronger inhibition observed under saline-alkali soil than normal soil. Moreover, AMF effects on rhizosphere soil properties included: 1) significant elevation in available phosphorus in both cultivars under two soil conditions; 2) increased soil CAT, phosphatase, and intertase activities in both cultivars in saline alkali soil; whereas 3) significant inhibition of soil enzymatic activities in HY22 under normal soil. These results indicated that compared to salt-sensitive cultivar, salt-tolerant cultivar might serve as more efficient symbiotic partner for AMF. AMF might demonstrate superior growth promotion in salt-tolerant cultivar, effectively exerting the synergistic effect of microbial regulation under saline-alkali soil.

Key words: arbuscular mycorrhizal fungi, root development, photosynthesis, soil enzyme activities, soil nutrients