Abstract
The application of pesticides is unavoidable in conventional agricultural practice. To develop effective biofertilizers, bacterial strains with both pesticide tolerance and plant growth-promoting (PGP) traits were isolated for further testing. Seedlings of rice (Oryza sativa) were planted in soil with 1, 5, or 10 times the recommended rates of the fungicides etridiazole, metalaxyl, and tricyclazole. Endophytic bacteria were isolated from roots of rice seedlings. The bacterial 16S rDNA sequences and related PGP characteristics including potential nitrogen fixation, phosphorus-solubilizing and indole acetic acid (IAA) production ability were further examined. In all, 17 different strains were obtained from rice seedling roots; five strains with both nitrogen fixation potential and IAA production ability included Rhizobium larrymoorei E2, Bacillus aryabhattai E7, Bacillus aryabhattai MN1, Pseudomonas granadensis T6, and Bacillus fortis T9. Except for T9, all strains could tolerate two or more fungicides. We inoculated rice roots with the endophytic bacteria and all conferred rice growth-promoting ability. Bacillus aryabhattai MN1 was further tested and showed high tryptophan dose-dependent IAA production ability, tolerance towards etridiazole and metalaxyl application and should be considered a potential bacterial biofertilizer.
Highlights
IntroductionConsiderable progress has been made in its cultivation, including breeding, nursery cultivation, fertilizer management and pest control, for one of the most representative crops in the world [1]
Rice is the largest crop cultivated in Taiwan and is a major source of food in Asia
This study aims at screening potential endophytic biofertilizers with fungicides tolerance and plant growth-promoting characteristics
Summary
Considerable progress has been made in its cultivation, including breeding, nursery cultivation, fertilizer management and pest control, for one of the most representative crops in the world [1]. Bacterial biofertilizers are plant growth-promoting rhizobacteria (PGPR) applied in the field to promote crop growth and reduce the need for synthetic fertilizers. Endophytic bacteria are defined as bacteria colonizing the internal tissues of plants (apoplasm or symplasm) without causing symptomatic infections or having negative effects on their host [3]. As compared with many rhizobacteria, endophytes have generally greater beneficial effects [4] and are less likely to encounter an extreme change of the soil environment because of the insulation of plants. To achieve better yield and protection of rice, the use of endophytic rather than rhizobacter biofertilizers, is preferred
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