The seed primer and biofertilizer performances of living Chlorella pyrenoidosa on Chenopodium quinoa under saline-alkali condition

Soil salinization and alkalization seriously restrict agricultural production. Biofertilizer can alleviate their impact and increase agricultural sustainability. However, the effects of living green microalgae on crop growth under saline-alkali stress are unclear. In this study, the unicellular green microalga Chlorella pyrenoidosa, used as a seed primer and a biofertilizer, was applied to investigate its effects on the growth characteristic of Chenopodium quinoa under artificial saline-alkali conditions (1:1 ratio of NaCl and NaHCO3) and natural saline-alkali soils. The seed primer experiment revealed that saline-alkali stresses inhibited seed germination and decreased seedling vigor index, root length and branch number, shoot length, and fresh weight of C. quinoa. Compared to the control, 25% and 50% doses of C. pyrenoidosa, however, increased the germination of C. quinoa seeds at the stresses of 100 mM and 200 mM saline-alkali concentrations by 29.3% and 12.6%, respectively. A 75% dose of algal cell enhanced the seedling characteristics and alleviated the inhibiting effects of saline-alkali stress on root and shoot length, seedling vigor index, and fresh weight of C. quinoa at 100 mM stress. In the biofertilizer experiment, the growth of C. quinoa was inhibited under saline-alkali soils; algal treatments improved the root length and branch number, shoot length, leaf size, and fresh weight of C. quinoa as well as soil available N, P, and K contents. A comprehensive analysis showed that 100% dose of algae exhibited a lower positive efficiency than 75% dose in the seed experiment. The present study demonstrated that living algal biofertilizer exerted the promoting effects on the germination and plant growth of crops under saline-alkali conditions.