Enhanced Biomass Production of Various Aquatic Duckweed Species Through the Inoculation of Plant Growth-Promoting Bacteria

Duckweed is a high-protein aquatic plant widely used for various fish feeds. Efforts to increase its biomass production can employ Plant Growth-Promoting Bacteria (PGPB). Therefore, this study aimed to determine the effect of inoculating Bacillus sp., Pseudomonas sp., and Rhizobium sp. on the biomass production of four duckweed species, including Landoltia punctata, Lemna perpusilla, Spirodela polyrrhiza, and Wolffia globosa. The bacterial inoculation was carried out by soaking three fronds of each duckweed species in bacterial suspension for 24 hours. The inoculated fronds were moved into a 50ml Erlenmeyer flask containing Hoagland medium and were incubated in a growth chamber at 25oC for 14 days with a 16-h/8-h day/night photoperiod at 5000 lux. The number of fronds, fresh weight, and dry weight of each duckweed species were recorded. Data obtained from the observations were analyzed statistically using the ANOVA method (P<0.05). The number of the fronds of four duckweed species co-cultured for 14 days with our PGPB collections increased by 1.2 to 4.6-fold compared with the uninoculated control. In addition, the treated/control ratio biomass for dry weight was around 1.3 to 3.0-fold. Moreover, all bacterial strains exhibited traits of Indole-3-acetic acid synthesis, nitrogen fixation and phosphate solubilization albeit with varying abilities. The co-culture between duckweed and PGPB demonstrated in this study could serve as a promise to increase the biomass production of several duckweed species to support fish feed production.