Zinc-Solubilizing Streptomyces spp. as Bioinoculants for Promoting the Growth of Soybean (Glycine max (L.) Merrill)

Abstract

Zinc-solubilizing bacteria can convert the insoluble form of zinc into soluble forms available to plants. This study was conducted to isolate and screen zinc-solubilizing actinobacteria from rhizosphere soils and to assess their effect on vegetable soybean growth. In total, 200 actinobacteria strains belonging to 10 genera were isolated from rhizosphere soil samples. Among these isolates, four showed zinc solubilization with solubilizing index values ranging from 3.11 to 3.78 on Bunt and Rovira agar supplemented with 0.1% zinc oxide. For the quantitative assay, in broth culture, strains CME34 and EX51 solubilized maximum available zinc contents of 529.71 and 243.58 μg/ml. Furthermore, indole-3-acetic acid (IAA) and ammonia were produced by these two strains, the strain CME34 produced the highest amount of IAA 4.62 μg/ml and the strain EX51 produced the highest amount of ammonia 361.04 μg/ml. In addition, the phosphate-solubilizing abilities in Pikovskaya’s medium of CME34 and EX51 were 64.67 and 115.67 μg/ml. Based on morphological and biochemical characterization and 16S rDNA sequencing, the strains CME34 and EX51 were closely related to the genus Streptomyces . In a greenhouse experiment, single-strain inoculation of Streptomyces sp. CME34 or EX51 significantly increased the shoot length, root length, plant dry weight, number of pods per plant and number of seeds per plant of vegetable soybean plants compared to the uninoculated control. These findings facilitated the conclusion that the two Streptomyces strains have potential as zinc solubilizers and can be suggested as bioinoculants to promote the growth and yield of soybean.

Harnessing the Power of Zinc-Solubilizing Bacteria: A Catalyst for a Sustainable Agrosystem

“…According to previous research, various strains of ZSB have been reported to play vital roles in Zn biofortification of some food crops. For instance, Burkholderia cepacia improved growth, grain yield, dry weight, and Zn acquisition in rice [66], Bacillus altitudinis in chickpea [48,67], B. tequilensis in wheat [62,68], and Pseudomonas spp. in tomato [69].…”

Indole-3-Acetic Acid Producing Yeasts in the Phyllosphere of Legumes: Benefits for Chili Growth

“…An indole derivative of the auxin family known as indole-3-acetic acid (IAA), a plant growth hormone, has undergone substantial studies and has been found to be the most prevalent auxin type in plants. IAA is synthesized, not only in plants but also in bacteria [13], yeast [10,11], actinomycetes [14] and filamentous fungi [15], and different levels of IAA production have been observed among microbial groups. IAA-producing yeasts include both Ascomycetous yeasts such as Candida spp., Cryptococcus spp., and Torulaspora spp.…”