Effect of different additives on seed bacterization of wheat inoculated with autochthonous Pseudomonas isolates

MELANI LORCH; BETINA AGARAS; CLAUDIO VALVERDE

Los Cocos, Córdoba, Argentina

Congreso; XVII Congreso Argentino de Microbiología General (SAMIGE); 2022

Pseudomonas genus contains a large number of species that are associated with plant growth promotion and biocontrol of pathogens. We have isolated and characterized a group of 19 pseudomonads from productive plots of the Argentine Pampas, which were selected by their antagonistic activity in vitro against different fungal pathogens. As microbial inoculants are generally applied before sowing in extensive crops, in this work we tested the survival ability of 6 isolates on wheat seeds, after 4 days post-inoculation (dpi). We studied different additives to improve on-seed stability and adherence. Strains were tagged with fluorescent proteins and a kanamycin resistance marker using a system based in Tn7 transposon, which delivers the DNA at a neutral chromosomal site. Bacterial suspensions (DO600=1,0) were mixed with non-disinfected wheat seeds Baguette 550, following the recommended dose (10 ml/kg), in presence or absence of a) 20% v/v of the commercial additive Premax® (Rizobacter, Argentina S.A., RASA); b) 20% v/v of Premax R® (RASA); c) 1M of trehalose (Tre) + 1,5% p/v of polyvinylpyrrolidone (PVP). Immediately after inoculation, we recovered bacteria from seed and quantified them on selective medium (day 0). Decay kinetics of the inoculant were carried out with treatments a) and c), in which recovery and enumeration of bacteria were performed daily, up to 4 dpi. We also evaluated the effect on germination. As positive control and reference, the commercial strain Pseudomonas sp. 1008 (Rizofos®, RASA) was included in the experiments.At day 0, Tre+PVP improved the recovery of RPAN1, SPAN5 and SVMP4 on seed surface (3,4×; 2,8×; 1,7×, respectively; LSD Fisher, p < 0,05), compared to the control without additive. At the same time, RPAN1 bacterization also was increased with Premax®, but RBAN4, SVBP6 and 1008 didn´t show any significant differences in presence of the additives. Particularly, Premax R® affected negatively the survival of SMMP3 at day 0. Seed germination was not affected by treatments. Counted CFU of RPAN1 and SPAN5 were higher than the control with Tre+PVP through all the kinetics (up to 4 dpi), and after 1 dpi in presence of Premax®. For SVBP6, the improvement was seen after 2 dpi with Premax®. The isolates SMMP3, RBAN4 and SVMP4 didn’t show differences with or without the additives.In conclusion, the effect of the additives was specie-dependent. As the isolates achieved a good bacterization level which was maintained during 4 dpi, we will perform a long term kinetics up to one month.