Role of <i>Rahnella aquatilis</i> AZO16M2 in Phosphate Solubilization and Ex Vitro Acclimatization of <i>Musa acuminata</i> var. Valery

Abstract

Rahnella aquatilis AZO16M2, was characterized for its phosphate solubilization capacity to improve the establishment and survival of Musa acuminata var. Valery seedlings under ex-acclimation. Three phosphorus sources (Rock Phosphate (RF), Ca3(PO4)2 and K2HPO4) and two types of substrate (sand:vermiculite (1:1) and Premix N°8) were selected. The factorial analysis of variance (p R. aquatilis AZO16M2 (OQ256130) solubilizes Ca3(PO4)2 in solid medium, with a Solubilization Index (SI) of 3.77 at 28 °C (pH 6.8). In liquid medium, it was observed that R. aquatilis produced 29.6 mg/L soluble P (pH 4.4), and synthesized organic acids (oxalic, D-gluconic, 2-ketogluconic and malic), Indole Acetic Acid (IAA) (33.90 ppm) and siderophores (+). Additionally, acid and alkaline phosphatases (2.59 and 2.56 µg pNP/mL/min) were detected. The presence of the pyrroloquinoline-quinone (PQQ) cofactor gene was confirmed. After inoculating AZO16M2 to M. acuminata in sand:vermiculite with RF, the chlorophyll content was 42.38 SPAD (Soil Plant Analysis Development). Aerial fresh weight (AFW), aerial dry weight (ADW) and root dry weight (RDW) were superior to the control by 64.15%, 60.53% and 43.48%, respectively. In Premix N°8 with RF and R. aquatilis, 8.91% longer roots were obtained, with 35.58% and 18.76% more AFW and RFW compared with the control as well as 94.45 SPAD. With Ca3(PO4)2, values exceeded the control by 14.15% RFW, with 45.45 SPAD. Rahnella aquatilis AZO16M2 favored the ex-climatization of M. acuminata through improving seedling establishment and survival.

Keywords

• pyrroloquinoline-quinone (PQQ) gene
• 16S gene
• tricalcium phosphate
• organic acids
• rock phosphate
• plant-growth-promoting rhizobacteria (PGPR)