Mitigating Salinity Stress in Pomegranate: Effects of Pseudomonas fluorescens and Glomus mosseae on Stress Responses of Red Angel and Wonderful Cultivars

Abstract

Salinity stress is a major challenge in modern pomegranate orchards. The application of biofertilizers is a promising strategy to mitigate the adverse effects of salinity stress and enhance the performance in pomegranates. This experiment was conducted in 2021 to investigate the effects of salinity stress (control, 4, and 8 dS/m) and inoculation with Pseudomonas fluorescens and Glomus mosseae, either individually or in combination (Pf+Gm), on Red Angel and Wonderful pomegranate cultivars. The results revealed a significant difference in the percentage of symbiosis and colonization among the biofertilizer treatments. Pf+Gm exhibited the highest percentages of symbiosis and colonization, followed by P. fluorescens. While salinity levels did not significantly affect symbiosis percentage, they had a detrimental effect on colonization percentage. Furthermore, biofertilizer treatments significantly increased leaf density, stem growth, total chlorophyll, and total anthocyanin, while reducing ion leakage and salinity damage index. In comparison to the non-inoculated control, the Pf+Gm treatment resulted in a 53.2 % decrease in ion leakage for the Red Angel cultivar and a 39.9 % decrease for the Wonderful cultivar. Salinity had a significant effect on proline production, with the Red Angel cultivar exhibiting the highest proline content (2.09 µmol/g) in response to salinity stress of 8 ds/m. However, biofertilizer treatments increased proline content in both cultivars. In Red Angel, the Pf+Gm treatment resulted in the highest proline production in the leaves (5.82 µmol/g), which was 123 % higher than that of the non-inoculated control. Additionally, the transpiration rate decreased with increasing salinity levels, and biofertilizer treatments had varying effects on photosynthetic gas exchange and electron transport rate. The interaction effect of biofertilizer treatments and salinity on CO2 absorption was highly significant, with Pf+Gm treatment exhibiting the highest absorption (8.51 and 8.61 µmol/m2/s in Red Angel and Wonderful, respectively). These findings suggest that applied biofertilizer treatments, especially Pf+Gm, can be an effective strategy for alleviating the negative effects of salinity stress on pomegranate cultivation.