Actinomycete diversity associated with cherry tree rhizospheres and their potential as microbial inoculants
Bibliographic record
Abstract
Cherry production in British Columbia, has increased dramatically over the past 20 years, representing about 96 % of the total Canadian crop. Increased cherry production, along with climate change, has brought new challenges to the Okanagan valley, such as limited water availability and increased soil-borne pathogens. When young cherry trees are planted to replace old apple or cherry orchards Replant Disease (RD) can arise, negatively affecting the establishment of new trees. In the Okanagan valley, RD has been linked to the presence of high populations of the plant-parasitic nematode Pratylenchus penetrans. Overcoming RD is critical for the successful establishment of high-density orchards; hence, environmentally-friendly methods are needed to manage the soil pathogens. The aim of this dissertation was to isolate multifunctional plant-growth-promoting (PGPR) and nematicidal bacteria from cherry rhizospheres, and to determine their possible mode of action. In addition, the potential of the isolated PGPR strains to induce drought resistance in plants was also assessed. Three Streptomyces and two Pseudomonas strains were isolated with potential to be used as microbial inoculants. The PGPR strains have nematicidal and antifungal activity, produce chitinases, proteases, the phytohormone indoleacetic acid, and the 1-aminocyclopropane-1-carboxylate (ACC) deaminase enzyme. The strains were also found to alleviate drought stress in drought-sensitive pepper plants. A second objective was to study the effect of different land management practices (composting, mulching), land-use history (old, new orchards), and fumigation on the abundance of chitinase chiC gene and the diversity of the actinobacterial communities. Chitinase chiC gene has been implicated as a mechanism of biocontrol through hydrolysis of both, nematode egg-shell and phytopathogenic fungal cell walls. The organic amendments did not increase chiC gene abundance, and there were no significant differences in the chiC gene copy number among old and new orchards. However, a higher chiC gene abundance was found in the adjacent non-cultivated soil indicating the detrimental effects of cherry cropping on bacterial chitinolytic populations. The addition of amendments and land-use history did not affect the actinobacterial diversity, in contrast, fumigation with Basamid, a chemical used to control nematodes, significantly decreased the actinobacterial diversity in the soils.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".