Banca de DEFESA: JULIA FERREIRA XAVIER

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
STUDENT : JULIA FERREIRA XAVIER
DATE: 08/10/2021
TIME: 09:00
LOCAL: videoconferência
TITLE:

Isolation and characterization of bacteria associated with the rhizosphere of halophyte plants.

KEY WORDS:

Rice, Halotolerant bacteria, Plant growth promotion, Saline soils.

PAGES: 72
BIG AREA: Ciências Agrárias
AREA: Agronomia
SUMMARY:

Most plant species, especially crops, do not tolerate recommended high salts. However, plants in the halophyte group are adapted to saline soils.In the rhizosphere of this group of halophyte plants, associations with microorganisms can promote plant growth and increase resistance to salt stress. Thereby, this work aimed to isolate and identify bacteria from the rhizosphere of halophyte plants from different saline environments in the state of Rio de Janeiro and to evaluate their capacity to promote growth. Samples of rhizospheric soils from halophyte plants Salicornia gaudicahudiana, Salicornia fruticosa, Blutaparon portulacoides, Sporobolus virginucus,and Cyperus ligularis were collected. Culture media added with 1%, 5%, 15%, 20%, and 25% of NaCl was used for bacterial isolation. The bacterial strains were classified according to growth at different NaCl concentrations and were identified by the MALDI-TOF MS technique and by rrs gene sequencing. The analysis of germination and root and shoot length of rice in different concentrations of salts was carried out to determine the ideal concentration that causes salt stress. Subsequently, the potential of nine strains of halotolerant bacteria belonging to the genus Pseudomonas and Bacillus in promoting rice growth at concentrations of 50 mM and 200 mM was analyzed. Thus, germination percentage, total root length, root volume, root contact surface, number of tips, and total shoot length were analyzed. A total of 315 bacteria classified as non-halophilic, halotolerant, and moderately halophilic were isolated. Of the isolated bacteria, 286 were analyzed by the proteomic technique MALDI-TOF MS, being identified at a safe level for genus 57% (165/286). Among the bacteria not identified by the MALDI TOF-MS technique, halotolerant and moderate halophilic isolates were selected for identification by the rrs gene sequencing. The inference of the genus and/or species was possible in 97.7% (43/44) of the isolates. The most abundant genera identified were Pseudomonas, Ochrobactrum, and Bacillus. At the concentration of 50 mM NaCl, the strains PA51 and PA164, belonging to the species Pseudomonas aeruginosa, provided an increase in most parameters analyzed compared to the non-inoculated treatment. Bacterial strains BS231, BT67, and B143 belonging to the species Bacillus subtilis, Bacillus thuringiensis, and Bacillus sp. respectively, promoted root elongation and a higher number of tips. At the concentration of 200 mM, the strains BS231 and BT294, belonging to the species Bacillus subtilis and Bacillus thuringiensis respectively, provided an increase in the total length of roots compared to the non-inoculated treatment. These results confirm that the rhizosphere of halophyte plants represents a promising environment for the isolation of halotolerant and halophilic bacteria. And that bacterial halotolerant strains Pseudomonas and Bacillus can promote the growth of rice plants under conditions in the presence or absence of salt stress.

BANKING MEMBERS:
Presidente - 1815763 - IRENE DA SILVA COELHO
Externo à Instituição - LUC FELICIANUS MARIE ROUWS - EMBRAPA
Interno - 387406 - RICARDO LUIZ LOURO BERBARA