Plant protection potential and ultrastructure of Bacillus subtilis strain 3A25

Strain 3A25 was isolated from Indian soil during a screening study for new plant protecting candidates. The present study further characterized this strain regarding its species identity, cellular ultrastructure and potential for protecting Brassica juncea against exposure to ozone. The strain was identified as Bacillus subtilis by 16S rDNA sequencing. Transmission electron microscopy revealed that strain 3A25 had intact bacterial flagella, endospores were found only occasionally. The growth-promoting capacity of strain 3A25 on B. juncea seedlings was investigated in a series of treatments with or without ozone stress in open top chambers. Chlorophyll content, shoot length, root length and leaf area were significantly increased by the treatment with B. subtilis 3A25. The ozone treatment (150 pbb) had a significant inhibiting effect on the development of B. juncea, however, the number of secondary roots was increased. Application of B. subtilis 3A25 either as foliar spray or directly on the soil significantly reduced the negative ozone effect, indicating that this strain has capacities in plant protection against environmental stress.

► Bacillus subtilis 3A25 has growth-promoting capacities in Brassica juncea seedlings.
► Ozone reduces chlorophyll content, leaf area, shoot and root length in B. juncea.
► Number of secondary roots is enhanced in B. juncea after ozone exposure.
► B. subtilis 3A25 treatment protects B. juncea seedlings from ozone damage.
► B. subtilis 3A25 has intact flagella, endospores are found only occasionally.