Biological nitrogen fixation and <i>nif</i>H gene expression in dry beans (<i>Phaseolus vulgaris</i> L.)
Bibliographic record
Abstract
Akter, Z., Pageni, B. B., Lupwayi, N. Z. and Balasubramanian, P. M. 2014. Biological nitrogen fixation and nif H gene expression in dry beans ( Phaseolus vulgaris L.). Can. J. Plant Sci. 94: 203–212. Dry bean (Phaseolus vulgaris L.) is one of the least efficient nitrogen (N2) fixers among legumes (approximately 30 to 50 kg N ha−1). To identify efficient N2 fixers, 22 dry bean genotypes were screened for symbiotic N2-fixation in potted low-N soil in the greenhouse under four treatments: (1) uninoculated, (2) inoculated with commercial Rhizobium leguminosarum bv. phaseoli inoculant Nitrastik-D®, (3) inoculated with commercial Rhizobium inoculant Nodulator®, and (4) fertilizer N added. Expression of nitrogenase reductase (nifH) gene in selected uninoculated genotypes (nodulated by indigenous rhizobia) was quantified by reverse transcription polymerase chain reaction (RT-PCR) to know if expression of this gene was an indicator of N2-fixation. Nitrogen fixation potential varied among the genotypes and between the rhizobia inoculants. Genotypes differed in shoot (5.17 to 8.39 g plant−1) and root (1.71 to 6.44 g plant−1) dry weights, nodule number (0 to 155 nodules plant−1) and mass (0.055 to 0.250 mg plant−1), and N2-fixed (0 to 129 mg N plant−1). Genotypes GH–196, FR 266 and AC Redbond fixed the most N2 (60 to 112 mg N plant−1) with either rhizobial inoculant, and Viva fixed the highest amount (129 mg N plant−1) when inoculated with Nitrastik-D. In contrast, AC Black Diamond, Island, Winchester, AC Polaris, LEF 2RB and SEA 5 had low N2-fixing potential (3 to 23 mg N plant−1) in inoculated treatments. The qRT-PCR analysis indicated that nifH gene expression was 5 fold higher in GH-196 compared to the non-nodulating mutant R99, which further confirmed the high N2-fixation capacity of GH-196. After confirmation in the field, dry bean genotypes with improved N2-fixation potential identified in this study may be used as parents in breeding programs in the development of future cultivars. The nifH gene expression may be used as a rapid test to select dry beans with high N2-fixation potential.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 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".