Effect of Seed Priming with Endophytic Bacillus subtilis on Some Physio-Biochemical Parameters of Two Wheat Varieties Exposed to Drought after Selective Herbicide Application

Abstract

Wheat plants are frequently exposed to combined herbicide and drought stress (HDS) which induces complex responses negatively, affects productivity, and is becoming more exacerbated with current climate change. In this work, we studied the influence of seed priming with endophytic bacteria Bacillus subtilis (strains 104 and 26D) on growth and tolerance of two wheat (Triticum aestivum L.) varieties (E70—drought tolerant; SY—drought susceptible) exposed to soil drought after application of selective herbicide Sekator® Turbo in pot experiments under controlled conditions; 17-day-old plants sprayed with herbicide and after 3 days were subjected to soil drought by stopping irrigating the plants for 7 days with subsequent resumption of normal irrigation (recovery). Additionally, the growth of tested strains (104, 26D) in the presence of different concentrations of herbicide Sekator® Turbo and drought (PEG-6000) were evaluated. It was established that both strains are herbicide and drought tolerant and capable to improve seed germination and early seedlings’ growth under different herbicide and drought stress degrees. The results of pot experiments showed that HDS exposure declined growth (plant length, biomass), photosynthetic pigments (chlorophyll a and b), leaf area, and increased lipid peroxidation (LPO) and proline accumulation in plants, demonstrating higher damaging effects for SY variety. Strains 104 and 26D mitigated (in different levels) such negative impacts of HDS on growth of both varieties by increasing length of roots and shoots, biomass, photosynthetic pigments (chlorophyll a and b), and leaf area, reducing stress-caused LPO (i.e., malondialdehyde), and regulating proline biosynthesis, as well as contributing to a faster recovery of growth, photosynthetic pigments, and redox-status of plants in post-stress period in comparison with non-primed plants. These ultimately manifested in forming a better grain yield of both varieties primed with 104, 26D, and exposed to HDS. Thus, both strains 104 and 26D (which are herbicide and drought tolerant) may be used as seed priming agents to improve wheat HDS tolerance and grain yield; however, strain 104 more effectively protected plants of E70, while strain 26D—plants of SY. Further research should be focused on understanding the mechanisms that determine the strain and variety-specificity of endophytic symbiosis and the role of bacteria in the modulation of physiological states of primed plants under stress conditions, including HDS.

Microbial Allies in Agriculture: Harnessing Plant Growth-Promoting Microorganisms as Guardians against Biotic and Abiotic Stresses

“…E70. B. subtilis 10-4 also decreased the accumulation of endogenous SA caused by dehydration, which was linked to the outcome of endophytes on growth, suggesting that endogenous SA may have contributed to the effects of B. subtilis in both cultivars [120].…”

Drought stress tolerance and growth promotion in chiltepin pepper (Capsicum annuum var. glabriusculum) by native Bacillus spp

“…Similarly, the effect of water stress on wheat plants with PEG (12%) was evaluated, and the isolates B. subtilis 104 and 26D increased the height by 7.89% in drought-sensitive varieties and 22.58% in drought-resistant varieties. Regarding root length, increases of 11.84% and 18.96% were reported in tolerant and sensitive varieties, respectively 74 .…”

The Effects of Seed Pretreatment with Endophytic Bacteria Bacillus subtilis on the Water Balance of Spring and Winter Wheat Seedlings under Short-Time Water Deficit

“…The mechanisms of beneficial action of PGP bacteria and fungi for plant organisms involve releasing a wide range of important secondary metabolites: phytohormones [ 10 , 19 , 23 , 24 , 25 , 26 ] and organic and amino acids [ 12 , 24 , 25 ]. PGP bacteria could also enhance: photosynthesis [ 17 , 27 , 28 , 29 ], the nutrient uptake by solubilizing inorganic elements [ 7 , 25 , 28 , 29 , 30 ]; the biosynthesis of siderophores [ 10 , 13 , 16 , 20 , 25 ]; antioxidant defense systems [ 7 , 13 , 25 , 28 , 29 ]; and stress-responsive genes expression [ 13 , 15 , 16 , 19 , 26 , 31 , 32 ] under the influence of stress factors. PGP bacteria also induced the synthesis of phytohormones auxins, cytokinins, gibberellins, salicylic acid, and abscisic acid (ABA) in plants [ 14 , 25 ].…”

“…Drought-stressed wheat plants inoculated by drought-tolerant Bacillus spp. have a higher viability due to their increased relative water content, photosynthetic pigments, osmolytes (proline), and decreased lipid peroxidation [ 26 , 27 ].…”

“…This makes it capable of the easy formulation and storage of Bacillus -based biological products. In recent times, it has been well-documented that B. subtilis interacts symbiotically or synergistically with host plants, representing a mutually helpful plant–bacteria interaction and possessing the ability to induce the growth and yield of plants under non-challenged growth and stress conditions [ 17 , 18 , 21 , 22 , 27 , 28 , 29 , 34 ]. Additionally, strains of B. subtilis are capable of colonizing the inner plant tissues (endophytes) considered to be more effective in plant stress protection than the rhizosphere strains (epiphytes) [ 34 ].…”