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Effects of Plant Growth-Promoting Rhizobacteria on Germination and Early Growth of Alfalfa (Medicago sativa) under Salt Stress Conditions
Marzie Soltani Alikooyi, Ali Abbasi Surki, Mohsen Mobini Dehkordi, Shahram Kiyani,
Volume 6, Issue 2 (3-2020)
Abstract



Extended Abstract
Introduction: Salinity is one of the most serious abiotic stresses, causing instability in germination and seed emergence due to low osmotic potential and ionic toxicity. Development of simple and low-cost biologic methods is essential for short-term management of salt stress. The use of plant growth-promoting rhizobacteria increases the rate and uniformity of germination. This research aimed to investigate the effect of bacterial growth-promoting bacteria on the germination and seedling growth indices of alfalfa c.v. Hamedani in different salinity levels.
Materials and Methods: A CRD factorial experiment with four replications was conducted in Seed Science and Technology Laboratory of Shahrekord University in 2016. The first factor consisted of 6 salinity levels 0, 2.5, 5, 7.5, 10 and 12.5 dS/m created with sodium chloride, and the second was four levels of bacterial pre-treatment: no inoculation with bacteria and biopriming, inoculation of alfalfa seeds with Acinetrobacter calcoaceticus PTCC 1318, Bacillus megaterium PTCC 1250 and Enterobacter aerogenes PTCC 1221. The seeds were treated with bacteria and placed at a 20 °C growth chamber. They were then irrigated with desired solutions depending on the salinity treatment. Germinated seeds were counted daily and the parameters of germination percentage and rate, seedling length, seedling dry weight, vigour index I, II and allometric coefficient were calculated after 10 days.
Results: Salinity levels higher than 10 dS/m reduced germination indices and seedling growth of alfalfa. The highest reductions were obtained for 12.5 ds/m salinity level versus control for germination percentage (10.81%), germination rate (49.48%), plumule and radicle length (13.30% and 28.88% respectively) and vigor index I and II, which were 30.27% and 6.28%, respectively. The seed treated with A. calcoaceticus was able to tolerate salinity stresses more than others. For example, the reduction for the seed treated with A. calcoaceticus was only 4%, compared with non-stressed control. In salinity conditions 2.5 and 5 dS/m, the highest rate of germination was obtained, using A. calcoaceticus bacteria. In addition, the seeds treated with E. aerogenes showed higher stability at different levels of salinity for seedling length traits. The highest vigour index related to the use of A. calcoaceticus in salinity was 7.5 ds/m.
Conclusions: A. calcoaceticus had a significant role in reducing the negative effects of salinity on germination percentage and rate, vigour index I and II and allometric coefficient while E. aerogenes bacteria were more effective in reducing negative effects of salinity on seedling length and dry weight.
 
 
Highlights:

  1. Acinetrobacter calcoaceticus bacterium increased the percentage and rate of germination of alfalfa seeds under salt stress.
  2. Enterobacter aerogenes bacteria efficiently adjusted the negative effects of salinity on alfalfa seedlings length and dry weight.

Interaction of Seed Priming, Sulfur, and Thiobacillus on Yield and Fatty Acid Profile of Sesame (Sesamum indicum) Seeds
Hasan Keshavarz, Barmak Jafari Haghighi, Abdolreza Jafari, Hamidreza Miri, Hamidreza Ebrahimi,
Volume 12, Issue 1 (9-2025)
Abstract
Objective: This study was conducted to investigate the effect of seed priming, sulfur application, and a biofertilizer containing Thiobacillus on seed yield and the fatty acid composition of sesame. Due to the importance of sesame as a valuable oilseed crop, evaluating the combined role of nutritional and biological management in improving both quantitative and qualitative traits of the crop holds significant importance.
Method: A field experiment was conducted during the 2023–2024 growing season in Fasa County, Fars Province, Iran, as a factorial arrangement in a randomized complete block design with three replications. Treatments included four seed priming methods (no prime, hydropriming, calcium chloride at 2.5% and 5%), four levels of sulfur application (0, 100, 200, and 300 kg ha-1), and three levels of Thiobacillus inoculation (0, 2, and 4 kg ha-1). Sesame cultivar ‘Darab 2’ was sown at a density of 40 plants m-2. Thousand-seed weight, dry matter and seed yield were measured. Oil quality was evaluated through fatty acid methyl ester analysis using gas chromatography according to ISIRI and AOAC standards.
Results: Seed priming, sulfur application, and Thiobacillus biofertilization significantly affected all the studied traits. Both two-way and three-way interactions were significant at 1% and 5% levels. The highest plant dry weight (23,580 kg ha-1) was observed in the treatment of hydro-priming combined with 300 kg ha-1 sulfur. Additionally, the highest thousand seed weight (5.33 g) and seed yield (2610 kg ha-1) were recorded in the treatment of hydro-priming combined with 300 kg ha-1 sulfur and 4 kg ha-1 Thiobacillus. The highest oil percentage (52.2%) and protein content (25.10%) were obtained in the treatment of 5% calcium chloride priming combined with 300 kg ha-1 sulfur and 4 kg ha-1 Thiobacillus. The fatty acid analysis revealed that integrated treatments increased the content of unsaturated fatty acids (linoleic, oleic, alpha-linolenic) while decreasing saturated fatty acids (palmitic and stearic).
Conclusions: The integrated use of seed priming (especially 5% calcium chloride or hydropriming), high-dose sulfur, and Thiobacillus inoculation significantly improved sesame seed yield, and oil quality. These practices enhanced nutrient uptake, stimulated microbial activity, and promoted biosynthesis of health-beneficial fatty acids.

Highlights
  • Seed priming, sulfur application, and Thiobacillus inoculation significantly increased sesame seed yield.
  • Combined treatments improved seed oil quality by increasing unsaturated fatty acids and reducing saturated ones.

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