Inoculation of phosphate solubilizing bacteria to mitigate the adverse effects of drought stress and phosphorus deficiency in peanut crops

LUDUEÑA L, ; OGGERO V, ; ANZUAY MS, ; BIANUCCI E,; CASTRO S,; TAURIAN T, ; FURLAN A.

Congreso; Congreso conjunto SAIB ? SAMIGE; 2021

In the province of Córdoba, the cultivation of peanut (Arachis hypogaea L.) has a high economic impact since more than 90% of the national production is concentrated there. However, it was reported that soils contain low contents of nitrogen (N) and phosphorus (P) and are prone to drought stress (DS) episodes. In these systems, plant growth-promoting bacteria exert beneficial effects on plants, among which the biological N2 fixation (BNF) and the solubilization of phosphates stand out. Peanut plants satisfy its N demand by the symbiotic association with Bradyrhizobium sp. Besides, phosphate solubilizing bacteria (PSB) contribute with the P demand and increase the efficiency of BNF. The objective of this study was to evaluate the effect of the mixed inoculation of PSB and a N2-fixing microsymbiont on peanut plants grown in the presence of the combined stresses of P and water deficit, on the colonization of PSB and biochemical indicators of DS tolerance. For this, peanut seedlings were grown in pots containing 250 g of sterile perlite:sand (2:1) in a greenhouse with controlled light and temperature conditions. All plants were inoculated with the N2-fixing strain Bradyrhizobium sp. SEMIA6144 (108 cfu ml-1). Treatments were: (1) inoculated with the PSB Serratia sp. S119 (109 cfu ml-1) or (2) Enterobacter sp. J49 (109 cfu ml-1) in substrates supplemented with an insoluble source of P (Ca3 (PO4)2 16 mM). The control plants were: (3) fertilized with an assimilable P source (20 mM K2HPO4), (4) supplemented with an insoluble P source (Ca3 (PO4)2 16 mM), (5) without supplemented P. The DS was carried out 35 days after sowing until the appearance of wilting symptoms in the plants. The control plants for the DS treatment were irrigated at field capacity. At harvest, colonization of PSBs in peanut roots was evaluated by counting bacterial cells from internal and external root tissues. Also, the relative water content (RWC) and chlorophyll and proline contents were determined as indicators of DS tolerance. Results obtained indicated that both inoculated PSBs were able to colonize and persist in peanut internal and external tissues at the end of the experience. Under DS and P deficiency, a lower number of PSB in external tissues than in inoculated plants grown with P deficiency and normal watering was found. On the other hand, the BSP strain J49 showed a higher number of cells in the internal tissues of peanut plants affected by DS and P deficiency conditions than in inoculated plants grown with P deficiency and normal watering. The RWC, chlorophyll and proline contents showed intermediate values in peanut plants inoculated with PSBs and exposed to DS, which were between values from un-inoculated plants grown in DS and well-watered plants. In conclusion, the higher capability of the BSP strain J49 to colonize root tissues in plants exposed to DS and P deficiency could contribute to plant tolerance, as revealed by some biochemical indicators.