Botany Department, Faculty of Science, Mansoura University, 35516, Mansoura, Egypt.
Botany Department, Faculty of Science, Tanta University, Tanta, 31527, Egypt.
Plant Physiol Biochem. 2022 Oct 15;189:24-34. doi: 10.1016/j.plaphy.2022.08.016. Epub 2022 Aug 22.
The current study aimed to scale up the favorable bio-stimulants for enhancing the growth and breeding strategies of Stevia rebaudiana to increase sugar productivity. Inoculation of 45-day-old S. rebaudiana plantlets with Bacillus cereus and Azospirillum brasilense alone or in combination for 30 days allowed comparisons among their effects on enhancement and improvement of plant growth, production of bioactive compounds and expression of steviol glycoside genes. B. cereus SrAM1 isolated from surface-sterilized Stevia rebaudiana leaves was molecularly identified using 16s rRNA and tested for its ability to promote plant growth. Beneficial endophytic B. cereus SrAM1 induced all plant growth-promoting traits, except solubilization of phosphate, therefore it showed high effectiveness in the promotion of growth and production of bioactive compounds. Treatment of plants with B. cereus SrAM1 alone revealed carbohydrates content of 278.99 mg/g, total soluble sugar of 114.17 mg/g, total phenolics content of 34.05 mg gallic acid equivalent (GAE)/g dry weight) and total antioxidants activity of 32.33 mg (A.A)/g dry weight). Thus, plantlets inoculated with B. cereus SrAM1 alone exhibited the greatest responses in physiological and morphological parameters, but plantlets inoculated with B. cereus SrAM1 + A. brasilense showed a maximal upregulation of genes responsible for the biosynthesis of steviol glycosides (Kaurene oxidase, ent-KO; UDP-dependent glycosyl transferases of UGT85C2, UGT74G1, UGT76G1). Taken together, the used bacterial strains, particularly B. cereus SrAM1 could significantly improve the growth of S. rebaudiana via dynamic interactions in plants.
本研究旨在扩大有利于甜菊生长和繁殖策略的生物刺激素，以提高甜菊糖的产量。将 45 天大的甜菊植物苗分别用单独的解淀粉芽孢杆菌和巴西固氮螺菌或混合菌（30 天）接种，以比较它们对增强和改善植物生长、生物活性化合物的产生和甜菊糖苷基因表达的影响。从表面消毒的甜菊叶片中分离到的解淀粉芽孢杆菌 SrAM1，通过 16s rRNA 进行分子鉴定，并测试其促进植物生长的能力。有益的内生解淀粉芽孢杆菌 SrAM1 诱导了所有的植物生长促进特性，除了磷酸盐的溶解，因此它在促进生长和生物活性化合物的产生方面非常有效。单独用解淀粉芽孢杆菌 SrAM1 处理植物，其碳水化合物含量为 278.99mg/g，总可溶性糖为 114.17mg/g，总酚含量为 34.05mg 没食子酸当量（GAE）/g 干重）和总抗氧化活性为 32.33mg（A.A）/g 干重）。因此，单独用解淀粉芽孢杆菌 SrAM1 接种的植物苗在生理和形态参数方面表现出最大的响应，但用解淀粉芽孢杆菌 SrAM1+巴西固氮螺菌接种的植物苗对负责甜菊糖苷生物合成的基因表现出最大的上调（贝壳杉烯氧化酶，ent-KO；UGT85C2、UGT74G1、UGT76G1 的 UDP 依赖性糖基转移酶）。总之，所使用的细菌菌株，特别是解淀粉芽孢杆菌 SrAM1，可以通过植物内的动态相互作用显著改善甜菊的生长。
