Piriformospora indica rescues growth diminution of rice seedlings during high salt stress

Abstract

Piriformospora indica association has been reported to increase biotic as well as abiotic stress tolerance of its host plants. We analyzed the beneficial effect of P. indica association on rice seedlings during high salt stress conditions (200 and 300 mM NaCl). The growth parameters of rice seedlings such as root and shoot lengths or fresh and dry weights were found to be enhanced in P. indica-inoculated rice seedlings as compared with non-inoculated control seedlings, irrespective of whether they are exposed to salt stress or not. However, salt-stressed seedlings performed much better in the presence of the fungus compared with non-inoculated control seedlings. The photosynthetic pigment content [chlorophyll (Chl) a, Chl b, and carotenoids] was significantly higher in P. indica-inoculated rice seedlings under high salt stress conditions as compared with salt-treated non-inoculated rice seedlings, in which these pigments were found to be decreased. Proline accumulation was also observed during P. indica colonization, which may help the inoculated plants to become salt tolerant. Taken together, P. indica rescues growth diminution of rice seedlings under salt stress.

Figure 1.P. indica colonization of rice roots. (A) Negative control inoculated with autoclaved P. indica shows no chlamydspores in the root cortex region. (B) Rice root segment showing colonization at 15 dpi. (C) Root colonization at 20 dpi. Fifteen days after P. indica inoculation, 60% colonization was detected. Control rice plants were mock treated with autoclaved P. indica and contained no spores. Arrow indicates a single chlamydospore of P. indica.

Figure 2.P. indica colonization. (A) Non-inoculated rice roots were thinner when compared with P. indica-inoculated rice roots. Strong, hard, and brownish roots were observed in P. indica-inoculated rice plants. (B) Root number in 25-d-old control plants and those inoculated by P. indica (15 dpi). Root numbers are higher in case of P. indica-inoculated rice. Each column represents the means of 3 measurements ± Standard Error.

Figure 3. Rice plants after 10 d salt stress. For representation purposes, one pot per treatment is shown. (A) For 200 mM and (B) for 300 mM salt stress. (a) Non-inoculated rice without salt treatment. (b) P. indica-inoculated rice without salt treatment. (c) Non-inoculated rice treated with 200 (300) mM salt. (d) P. indica-inoculated rice treated with 200 (300) mM salt.