An endophytic Pseudomonas sp. of Piper tuberculatum promotes growth on Piper nigrum through increase of root biomass production

摘要

Microorganisms that can positively influence plants have emerged as a powerful tool for sustainable agriculture. Previous studies identified a Pseudomonas sp. (Pt13) associated with the roots of Piper tuberculatum, a member of the Piperaceae occurring in the Amazon region with known resistance to infection by Fusarium solani f. sp. piperis, which causes root rot in black pepper (Piper nigrum L.). Pt13 was able to inhibit the in vitro growth of this pathogen by 55.31%; however, studies on P. nigrum as a host plant of Pt13 are lacking. Therefore, we aimed to evaluate the effects of Pt13 inoculation on P. nigrum growth under greenhouse conditions. The experiments comprised two treatments (inoculated and control) with 10 replicates per treatment and samplings at 30, 60 and 90 days post inoculation (dpi). Results revealed that the plants inoculated by immersion of roots in bacterial suspension showed no physiological differences in comparison to the control plants at 30 dpi. However, when these plants were submitted to additional inoculations through irrigation of soil with bacterial suspension repeated every 10 days, they showed an increment of 32% and 49% in net CO2 assimilation rate and 23.94% and 42.78% in total chlorophyll content at 60 and 90 dpi, respectively. At 90 dpi, the inoculated plants showed an increase in the specific leaf area at 43,23%, total leaf area at 56%, root dry mass at 29% and total dry mass at 15%. Thus, results confirmed that Pt13 improved the photosynthetic efficiency, resulting in increased biomass production. Results obtained here will be useful in future studies of interaction with F. solani f. sp. piperis.