Dominant Root Associated Fungi (RAF) from Drynaria quercifolia L. either Induce or Retard Growth of PSB Rc10 Rice (Oryza sativa L.) in Gibberellic Acid-Inhibited Medium

Abstract

The testing and use of microorganisms for in vitro growth promotion of agriculturally significant crops such as rice has increased but remains underexploited. The current study aims to explore growth-enhancing mechanisms of dominant root-associated fungi (RAF) isolates from Drynaria quercifolia and test their effects on rice. The most abundant RAF on five tree-collection sites were cultured in vitro. Genomic DNA of the RAF were extracted and the ITS (internal transcribed spacer) region of the 18S ribosomal DNA (rDNA) were sequenced and molecularly identified. Two RAF isolates significantly increased the plant shoot/total length (Meyerozyma guilliermondii: 10.29±4.18/13.46±4.18 cm; Trichoderma simmonsii: 10.33±1.38/13.23+1.58 cm), shoot/total fresh weight (Meyerozyma guilliermondii: 57.33±15.76/71.00±16.10 mg; Trichoderma simmonsii: 63.22±12.23/76.00±10.67 mg) and shoot/total dry weight (Meyerozyma guilliermondii: 16.99±6.74/22.78±7.41 mg; Trichoderma simmonsii: 16.89±3.33/23.11±5.30 mg) weight compared to the negative control. These results possibly show the ability of the two isolates to produce the hormone gibberellic acid. On the other hand, three of the RAF isolates did not significantly increase seedling growth and biomass. The Trichoderma yunnanense (shoot: 0.36±0.16 cm; total: 0.53±0.20 cm), unidentified Mucoromycotina isolate F₅P₁RAF₁₆ (shoot: 1.87±0.59 cm; total: 2.12±0.58 cm) and the unidentified Mucoromycotina isolate F₉P₂RAF₂₁ (shoot: 3.26±1.56 cm; total: 5.19±2.00 cm) approximated the growth of rice seedlings inoculated with broth and water negative control (shoot: 4.40+2.27 cm; total: 6.38+2.28 cm). This possibly indicates the inability of these isolates to produce GA or their potential ability to produce growth-retarding metabolites. Preliminary data from this study reveal potential growth-promoting capacity of RAF isolates on rice.