Bacterial endophytes from arid land plants regulate endogenous hormone content and promote growth in crop plants: an example of Sphingomonas sp. and Serratia marcescens

[摘要] The objective of the present study was to determine the potential plant growth-promoting action of bacterial endophytes isolated from arid land-dwelling plants under normal conditions. Overall, five bacterial endophytes LK11 ( Sphingomonas sp. LK11), TP5 ( Bacillus subtilis ), MPB5.3 ( B. subtilis subsp. Subtilis ), S9 ( B. subtilis subsp. Subtilis ), and TP1 ( Serratia marcescens ) were evaluated based on morphological characteristics after isolation and purification. Phytohormonal analysis of these endophytes predicted indole acetic acid (IAA) production 12.31 ± 0.45 , 6.8 ± 0.59, and 10.5 ± 1.02 μM/mL in the culture broths of LK11, MPB5.3, and TP1, respectively. Under controlled greenhouse conditions, these endophytes were inoculated into soybean, and their growth-promoting characteristics were compared with those of non-phytohormone-producing endophytes. In terms of plant growth promotion, among IAA-producing endophytes, LK11 and TP1 greatly improved physiological characteristics such as shoot/root length, fresh/dry weight, and chlorophyll contents. However, the non-phytohormone-producing endophytes TP5 and S9 did not show a growth-promoting effect. Based on these results, plants inoculated with LK11 and TP1 along with a control were subjected to endogenous hormonal analysis and showed a significant increase in abscisic acid (457.30–398.55 vs. 205.93 ng/g D.W.) and a decrease in jasmonic acid content (50.07–85.07 vs. 93.90 ng/g D.W.), respectively. Total gibberellin content was found to significantly increase in endophyte-inoculated plants (155.43–146.94 ng/g D.W.) as compared to that in controls (113.76 ng/g D.W.). In summary, bacterial endophytes might be used to enhance crop plant physiological characteristics isolated from arid land-inhabiting plants under normal conditions.

[学科分类] 纳米科学和纳米技术

[关键词] Endophytes;soybean;phytohormones;agronomic crops;hormonal regulation;plant growth characteristics;environmentally friendly agriculture