COMPARED CO-INOCULATION OF MAIZE (Zea mays L.) WITH Azospirillum argentinense AND FLUORESCENT Pseudomonas UNDER CONTROLLED GROWTH AND IN THE FIELD

MARCOS VALLE FJ; MARTINEZ ROBERTO DIONISIO; FERNANDEZ MACARENA; GOYA, VANESSA; PAGNUSSAT LA; CREUS CECILIA; MARONICHE, GUILLERMO

Congreso; SAMIGE 2023; 2023

The use of plant growth promoting bacteria (PGPB) to inoculate crops is a promising fieldof research in agriculture as a sustainable approach to reduce chemical fertilization. Thebacterial groups Azospirillum argentinense and fluorescent Pseudomonas have been thesubject of numerous studies due to the beneficial effects they generate on plant growth.Although these PGPB are commonly formulated mixed in commercial inoculants, there arefew studies that evaluate the compatibility and performance of the strains when combined.In this work, we compared the effect of different strain combinations of Azospirillum andPseudomonas on maize vegetative growth under controlled conditions and in the field. Twoparallel maize inoculation trials were carried out in a growth chamber (25°C with light:darkcycle of 16:8 h) and in a field in Balcarce (EEA INTA Balcarce, Buenos Aires, Argentina)during season 2022/2023. Maize seeds (Nidera AX 7784 VT3P) were inoculated with 10 µlper seed (final dose: 107 CFU.seed-1 of each strain) of the combinations A. argentinenseAz39 + P. fluorescens A506; A. argentinense Az19 + P. fluorescens A506; A. argentinenseAz39 + P. putida LSR1; A. argentinense Az19 + P. putida LSR1; A. argentinense Az39 + P.rhodesiae ZME4; A. argentinense Az19 + P. rhodesiae ZME4 or saline solution as anegative control. The seeds were sown on 12/16/22 in a field under irrigation and no-tillageconditions, or in 0.2 L pots (containing the same soil as the experimental field) for the growthchamber assay. The growth and phenological parameters evaluated included plant height(PH), root length (RL), root dry weight (RDW), and aerial dry weight (ADW). Undercontrolled conditions, aerial growth was stimulated by both AZ19/ZME4 and AZ39/ZME4combinations, resulting in higher PH and ADW. The highest ADW corresponded toAZ19/ZME4. No significant differences were found in RL and RDW between the differenttreatments. In the field trial, AZ39/ZME4 presented the lowest PH while the highest plantswere those inoculated with AZ39/A506 and AZ19/A506. In stages V9 and R1, there wereno differences in ADW between treatments. However, the AZ39/ZME4 combinationregistered a higher ADW in stage R4 when compared to the non-inoculated controltreatment. Moreover, the inoculation with AZ39/ZME4 showed the highest biomass of tillers.Taken together, the results indicate that the Pseudomonas genotype is a major determinantof inoculant efficacy, being strain ZME4 (a maize endophyte) the most beneficial strain formaize under controlled conditions. In the field, there was no unanimity in regards to the beststrain for stimulating maize growth, being A506 the most beneficial on the height andAz39/ZME4 combination the only treatment that increased biomass. We conclude thatAzospirillum+Pseudomonas maize co-inoculation in the growth chamber is not a reliablesystem to predict the inoculant performance in the field.