Table 2. Effect of [14C] glyphosate spray before spore inoculation on leaf rust rating and correlation with glyphosate tissue concentration in GR wheat cv. Ingot.
| Leaf rust rating and glyphosate tissue concentrations
|
Treatment
|
|||
|---|---|---|---|---|
| A | B | C | D | |
| Plant leaf stage at glyphosate spray* | 5 | 3 | 5 | 3 |
| Plant leaf stage at spore inoculation† | 7 | 5 | 5 | 3 |
| Glyphosate spray timing, DBI‡ | 14 | 14 | 1 | 1 |
| % Leaf rust rating, avg (SE)§ | ||||
| % Pustules, no spray | 28.8 (2.8) | 26.0 (1.9) | 27.0 (1.2) | 24.0 (3.7) |
| % Pustules, 1× glyphosate spray | 0.4 (0.2) | 0.2 (0.1) | 0 | 0 |
| % Lesions, 1× glyphosate spray | 90 | 40 | 10 | 10 |
| Tissue glyphosate in μg/g, avg (SE)¶ | ||||
| Inoculated leaf, 0 DAI | 10.4 (2.1) | 9.3 (3.5) | 41.8 (4.4) | 59.3 (13.5) |
| Inoculated leaf, 13 DAI | 8.0 (1.3) | 9.3 (1.5) | 29.9 (6.5) | 41.2 (7.0) |
| Plant foliage, 13 DAI | 10.1 (2.0) | 7.3 (2.0) | 76.7 (13.4) | 60.5 (10.6) |
| Roots, 13 DAI | 8.6 (1.3) | 5.7 (1.4) | 23.6 (5.0) | 33.9 (6.3) |
*
Roundup WeatherMAX (0.84 kg ae/ha in 187 liters/ha vol, 1×) containing [14C]glyphosate was sprayed OT.
†
Leaf rust spores were suspended in oil and applied onto a single mature leaf on each plant.
‡
Roundup was sprayed before spore inoculation 14 or 1 DBI.
§
The inoculated leaf was rated 13 DAI for percentage of leaf area with sporulating lesions (i.e. pustules) or percent incidence of lesions without sporulation. The results are the average of five plants and SE.
¶
The inoculated leaf, after washing to remove surface residues, was combusted to recover radioactivity and translated to glyphosate concentration (μg/g fresh weight). The results are the average of five plants and SE.