Bactérias prospectadas da tiririca (Cyperus rotundus L.) promovem o desenvolvimento de plantas de soja e milho

Abstract

Plant growth-promoting bacteria (PGPB) constitute a broad group of microorganisms which, when associated with plants, exhibit significant potential due to the benefits they confer to the growth and development of various plant species. This study aimed to evaluate the interaction of PGPB, bioprospected and isolated from purple nutsedge (Cyperus rotundus L.), on the germination and development of soybean and maize plants. Three trials were conducted for both crops, including experiments in a BOD (Biochemical Oxygen Demand) chamber and a greenhouse. The BOD and sand tray experiments followed a completely randomized design with 10 treatments and five replicates: T1 - control; T2 - Azospirillum brasilense; T3 - Terribacillus sp. (SN17); T4 - Pantoea ananatis (S30N); T5 - P. eucrina (BiF); T6 – Bacillus sp. (E9E); T7 - B. licheniformis (SN33); T8 – B. licheniformis (SC19_1); T9 – B. subtilis (E3E); and T10 – B. zhangzhouensis (E5E). The pot experiment was set up in a randomized block design with six treatments selected based on previous germination and early development performance: T1 - control; T2 – A. brasilense; T5 - P. eucrina; T6 – Bacillus sp.; T9 – B. subtilis; and T10 – B. zhangzhouensis, with six replicates. In the BOD test, germination percentage (first and second count), percentage of normal, abnormal, and dead seedlings, and germination speed index (GSI) were assessed. In the early development phase, emergence speed index (ESI), germination percentage, initial plant growth, relative chlorophyll content, leaf area, plant height, stem diameter, root length, and shoot and root dry mass were evaluated. In the pot trial, morphometric traits, relative chlorophyll content, gas exchange, number of rows per ear and grains per ear (maize), and number of pods per plant and grains per pod (soybean) were measured. In soybean, in the BOD test, T10, T4, T7, T6, and T3 showed superior performance in the first count compared to the control (T1), with no significant differences in other variables. In sand, T9 showed higher values in first count, second count, and ESI, outperforming T1; T8, T7, T6, and T4 promoted greater plant height; T9 had greater root length and stem diameter; T7 showed higher leaf area and shoot dry mass; and T10 resulted in greater root dry mass. In pots, T2 showed the highest hundred-grain weight, and T6 the highest CO₂ net assimilation rate, outperforming T2 and T5. For maize, in BOD, the highest percentage of normal seedlings was observed in T1, with intermediate performance from T6 and T9, while T7 and T4 showed a higher proportion of abnormal seedlings. In sand, T7 showed greater plant height and root length; T8, greater leaf area and shoot dry mass; T3, higher root dry mass; and T10, larger stem diameter. In pots, all inoculated treatments outperformed the control in plant height; T6 had the greatest leaf area, outperforming T9 and T10; T9 had the highest number of rows per ear; and T2 showed the highest net photosynthetic rate, outperforming only T10. It is concluded that B. subtilis was promising for early soybean seed development; B. zhangzhouensis and B. licheniformis enhanced morphometric traits in nutrient-poor substrates; and A. brasilense increased grain yield. In maize, B. licheniformis promoted plant growth by increasing plant height, root length, leaf area, and shoot biomass, while Terribacillus sp. enhanced root biomass accumulation.