Tobacco root galling due to nematodes is not widespread in France, but affects locally some farms. In 2014, two farms about 300 km distant from each other, one in Charente Maritime and one in Aveyron, were identified as having heavy root galling problems. Soil samples were sent to the ANSES nematology laboratory (35653 le Rheu, France), and in both cases Meloidogyne arenaria was identified. A set of flue-cured genotypes, including the resistant lines NOD8 and RL 2-1-1, formerly tested in the CORESTA nematode collaborative study, and the susceptible standard ITB 683, were installed in these farms using a randomized blocks design. Recommended practices for filler flue-cured tobacco were applied. The percent of the root system affected by galls was assessed on 8 individual plants in each plot, respectively 126 and 123 days after planting, using the following scale: 0: no galling, 1: 1 to 2% of the root system with galls, 2: 3 to 10%, 3: 11 to 30%, 4: 30 to 50%, 5: 50 to 80%, 6: 80 to 100%.

Results were highly similar in both locations. The susceptible standard ITB 683 was heavily attacked, with 70 to 100% of the root system with galls. In sharp contrast, RL 2-1-1 showed nearly no galling (average scores 0.44 and 0.38, respectively). NOD 8 had an intermediate result, with between 3 and 30% of the root system affected (mean score 2.03). In average of both locations, breeding lines had mean scores from 1.9 to 5.4, while the cultivar CETARSA 613 showed an average score equal to 4.0.

Considering that no soil fumigations are authorized for controlling gall nematodes in tobacco fields in France, breeding gall nematode resistant cultivars appears highly necessary, even when the pathogen is not widespread. These results will help in obtaining such cultivars. (Reprinted with permission)