Role of bioinoculants and auxin in development of salt tolerant Mentha arvensis

Abstract

Pot experiments were conducted for the development of salt tolerant Mentha arvensis (Japanese mint, family: Labiatae) saplings involving bioinoculants, namely Arbuscular Mycorrhizal (AM) fungi, Azotobacter and an auxin – Indole Acetic Acid (IAA). The IAA and sodium chloride (NaCl) concentrations were standardized prior to the experiments. The 10-ppm IAA and 0.08% NaCl (w/v) were found to be optimum in combination with AM fungi and Azotobacter to increase all the growth parameters and microbial count in the rhizosphere. For development of salt tolerant saplings, the optimal concentration of IAA, along with AM fungi and Azotobacter in different combinations, was applied in pots. The saplings were irrigated regularly with 0.08% NaCl water. Although plant growth, AM infection percentage, AM spores/100 g soil and Azotobacter cells/g soil were affected by NaCl watering, the inoculation of both bioinoculants significantly enhanced survival percentage of saplings from 10 to 40% under salt stress. Maximum survival (40%) of saplings was found with IAA (10 ppm) + AM fungi + Azotobacter treatment.