Effects of microbial biostimulants (Trichoderma album and Bacillus megaterium) on growth, quality attributes, and yield of onion under field conditions

Nabil A Younes; Touhidur Rahman Anik; Md Mezanur Rahman; Ahmed A Wardany; Mona F A Dawood; Lam-Son Phan Tran; A A H Abdel Latef; Mohammad Golam Mostofa

doi:10.1016/j.heliyon.2023.e14203

Effects of microbial biostimulants (Trichoderma album and Bacillus megaterium) on growth, quality attributes, and yield of onion under field conditions

Heliyon. 2023 Mar 2;9(3):e14203. doi: 10.1016/j.heliyon.2023.e14203. eCollection 2023 Mar.

Authors

Nabil A Younes¹, Touhidur Rahman Anik², Md Mezanur Rahman², Ahmed A Wardany³, Mona F A Dawood⁴, Lam-Son Phan Tran², A A H Abdel Latef⁵, Mohammad Golam Mostofa⁶

Affiliations

¹ Horticulture Department, Faculty of Agriculture, Al-Azhar University, Assiut Branch, Assiut 71524, Egypt.
² Institute of Genomics for Crop Abiotic Stress Tolerance, Department of Plant and Soil Science, Texas Tech University, Lubbock, TX 79409, USA.
³ Botany and Microbiology Department, Faculty of Science, Al-Azhar University, Assiut 71524, Egypt.
⁴ Botany and Microbiology Department, Faculty of Science, Assiut University, Assiut 71516, Egypt.
⁵ Botany and Microbiology Department, Faculty of Science, South Valley University, 83523 Qena, Egypt.
⁶ Department of Energy Plant Research Laboratory, Michigan State University, East Lansing, 48824, Michigan, USA.

Abstract

Microbial biostimulants (MBs) promote plant growth and stress tolerance in a sustainable manner. However, precise field trials of MBs are required in natural setting with a range of crop varieties to harness the benefits of biostimulants on crop yield improvement. This study investigated the effects of two MBs, Trichoderma album and Bacillus megaterium, on an onion cultivar's growth, nutritional qualities, antioxidant properties, and yield potentials under field conditions for two successive years. Before transplantation, onion bulbs were gelatin-coated with 2.0 and 4.0 g L^-1 of each of the MB. Results revealed that MBs-pretreated onion plants exhibited better growth indices, photosynthetic pigment contents, and yield-attributing features like bulb weight than control plants. Nutraceutical analysis demonstrated that T. album-pretreated (by 2.0 g L^-1) onion cultivar enhanced the level of K⁺ (by 105.79%), Ca²⁺ (by 37.77%), proline (by 34.21%), and total free amino acids (by 144.58%) in bulb tissues over the control plants. Intriguingly, the pretreatment with both T. album and B. megaterium (by 2.0 g L^-1) increased the levels of total soluble carbohydrates (by 19.10 and 84.02%), as well as antioxidant properties, including increased activities of superoxide dismutase (by 58.52 and 31.34%), catalase (by 164.71 and 232%), ascorbate peroxidase (by 175.35 and 212.69%), and glutathione-S-transferase (by 31.99 and 9.34%) and improved the contents of ascorbic acid (by 19.1 and 44.05%), glutathione (by 6.22 and 33.82%), and total flavonoids (by 171.98 and 56.24%, respectively) in the bulb tissues than control plants. Although both MBs promoted the growth and nutraceutical qualities of onion bulbs, T. album pretreatment showed better effects than that of B. megaterium in the field settings. Based on the morphophysiological attributes and biochemical properties, a low dose (2.0 g L^-1) was more effective than a high dose (4.0 g L^-1) of T. album in promoting onion growth. Overall, the current research findings imply that T. album might be a potential MB in improving growth and quality attributes, and hence the productivity of onion cultivars under field circumstances.

Keywords: Antioxidant properties; Bacillus megaterium; Microbial biostimulants; Nutrition; Onion; Trichoderma album; Yield.