In Vitro Growth-promoting Properties of Non-dominant Root Symbiotic Fungi (ND-RSF) from Drynaria quercifolia L. and their Effects on PSB Rc10 Rice (Oryza sativa L.)

Abstract

The use of microorganisms as an environmentally safe method for agricultural crop production and biocontrol has increased in recent years but is still considerably underexploited. This study explored the potential growth-promoting properties of non-dominant root symbiotic fungal (ND-RSF) isolates from Drynaria quercifolia L. and their effects on rice. The five molecularly identified ND-RSF isolates induced indole-3-acetic acid (IAA) production spectrophotometrically at 530 nm. The Trichoderma scalesiae isolate produced the highest IAA per unit volume of culture broth and the highest IAA per unit of dry weight. All five ND-RSF isolates have phosphate solubilization activity. Three ND-RSF isolates significantly increased the total length of paclobutrazol, a gibberellic acid (GA) inhibitor, treated rice plants. The fresh weight of rice inoculated with Aspergillus brunneoviolaceus is significantly heavier than the negative broth and water control. The dry weight of rice inoculated with Aspergillus aculeatus, Aspergillus japonicus, and Aspergillus brunneoviolaceus are significantly higher compared to the positive controls (20 PPM GA, 20 PPM IAA, and non-paclobutrazol treated rice seedlings). The results indicate the ability of these three Aspergillus isolates to synthesize the GA hormone. The ability of these ND-RSF isolates to produce growth-promoting hormones auxin and GA, plus their ability to solubilize inorganic phosphate are evidence to their potential growth-promoting abilities toward their host plant. This present study also implies that these ND-RSF can be growth-promoting mutualists to rice.