Plant Growth-Promoting Traits in Enterobacter cloacae subsp. dissolvens MDSR9 Isolated from Soybean Rhizosphere and its Impact on Growth and Nutrition of Soybean and Wheat Upon Inoculation

Abstract

Microbially mediated nutrient mobilization and its acquisition is gaining significance in recent years particularly in low-input, sustainable crop production systems, and improvement of soil health. In this study, a rhizobacterial isolate MDSR9 was recovered from the rhizosphere of soybean genotype “PK 1024” and was identified as Enterobacter cloacae subsp. dissolvens on the basis of phenotypic, fatty acid methyl esters characteristics, and 16S rRNA gene sequence. Isolate MDSR9 showed multiple plant growth-promoting traits like production of indole-3-acetic acid (IAA), siderophore, and ammonia; phytate mineralization, solubilization of phosphate, potassium, and zinc but did not show 1-aminocyclopropane-1-carboxylate (ACC) deaminase activity and HCN production traits. Inoculation of isolate MDSR9 significantly decreased pH and increased auxin content and enzyme activities in the rhizosphere soil, and enhanced nutrient concentration in shoot and roots of soybean (R5 stage) and wheat (panicle initiation) grown under microcosm conditions. At maturity, inoculation significantly enhanced shoot and seed weight up to 13.77 and 16.09 %, respectively, in soybean, and 39.13 and 49.14 % in wheat over un-inoculated control. A significant increase in macro- and micro-nutrient concentration was recorded in shoot and seeds of inoculated soybean and wheat crops. However, the magnitude of response varied both in shoots and seeds; inoculation in soybean shoots showed higher concentration of micronutrients (Fe, Cu, and Mn), whereas wheat shoots showed higher concentration of macronutrients (N, P). On the contrary, comparatively higher inoculation responses toward micronutrient concentration in the seed was obtained in wheat than in soybean. It indicates that inoculation of this multiple-traits-bearing-strain has potentially contributed to nutrient mobilization in both the crops and consequently improved crop yield. Hence, it is suggested that the rhizobacterial isolate MDSR9 can be utilized as a potential PGPR for enhancing the productivity of soybean–wheat system after field validation.