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

LUDUEÑA, LILIANA; OGGERO V; ANZUAY, MARÍA SOLEDAD; BIANUCCI ELIANA; CASTRO STELLA; TANIA TAURIAN; FURLAN ANA

Congreso; LVII SAIB Meeting - XVI SAMIGE Meeting; 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) andphosphorus (P) and are prone to drought stress (DS) episodes. In these systems, plant growth-promoting bacteria exertbeneficial 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 solubilizingbacteria (PSB) contribute with the P demand and increase the efficiency of BNF. The objective of this study was to evaluatethe effect of the mixed inoculation of PSB and a N2-fixing microsymbiont on peanut plants grown in the presence of thecombined 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 andtemperature 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) insubstrates supplemented with an insoluble source of P (Ca3 (PO4)2 16 mM). The control plants were: (3) fertilized with anassimilable P source (20 mM K2HPO4), (4) supplemented with an insoluble P source (Ca3 (PO4)2 16 mM), (5) withoutsupplemented P. The DS was carried out 35 days after sowing until the appearance of wilting symptoms in the plants. Thecontrol plants for the DS treatment were irrigated at field capacity. At harvest, colonization of PSBs in peanut roots wasevaluated by counting bacterial cells from internal and external root tissues. Also, the relative water content (RWC) andchlorophyll and proline contents were determined as indicators of DS tolerance. Results obtained indicated that both inoculatedPSBs were able to colonize and persist in peanut internal and external tissues at the end of the experience. Under DS and Pdeficiency, a lower number of PSB in external tissues than in inoculated plants grown with P deficiency and normal wateringwas found. On the other hand, the BSP strain J49 showed a higher number of cells in the internal tissues of peanut plantsaffected 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, whichwere between values from un-inoculated plants grown in DS and well-watered plants. In conclusion, the higher capability ofthe BSP strain J49 to colonize root tissues in plants exposed to DS and P deficiency could contribute to plant tolerance, asrevealed by some biochemical indicators.