Nathalie Dauphinais

Pearl Millet for the Management of Pratylenchus penetrans in Flue-Cured Tobacco in Quebec

Two 1-year rotation experiments were conducted from 1998 to 2000 to assess the impact of forage and grain pearl millet (Pennisetum glaucum) on Pratylenchus penetrans populations in a tobacco field (Nicotiana tabacum cv. Delgold) in Quebec. Performance of these crops was compared with rye, the standard rotation crop. Rye plots were doubled to include a fumigated standard (application of metham sodium at 67.4 liters/ha on a band). Forage pearl millet increased tobacco yields by an average of 103% compared with nonfumigated rye. In 2000, leaf dry weights of tobacco following grain pearl millet CGPM H5 and CGPM H6 was increased by 70 and 73%, respectively, when compared with nonfumigated rye and were not significantly different from the fumigated plots following rye. Forage and grain pearl millet should be considered as a viable alternative to fumigation for controlling P. penetrans infestation in flue-cured tobacco production in Quebec.

Evaluation of cultural methods for the management of the golden nematode (Globodera rostochiensis) in Quebec, Canada

Abstract Potato cyst nematodes are a major threat to potato production worldwide. In 2006, the isolation of the golden nematode, Globodera rostochiensis, in Quebec, Canada, led to the establishment of a quarantine area and the initiation of a research programme for the sustainable management of this regulated pest. In this study, the field efficacy of crop rotations and soil amendments was assessed in microplots for their potential to reduce populations of G. rostochiensis in the quarantine area. Crop rotation with a resistant potato cultivar was very effective in decreasing the population density of G. rostochiensis in soil. A single year with a cultivar carrying the H1 resistance gene reduced nematode populations by 62–95%. After 3 consecutive years of cropping to resistant potato, the number of viable eggs was zero in several microplots, and the overall population reduction was around 95%. Natural population decline with the cultivation of a non-host crop such as corn was around 30% per year. Trap cropping also showed reduced G. rostochiensis populations with results similar to the resistant cultivar. Sticky nightshade could not be established under Quebec’s climatic conditions and therefore was not a viable alternative for managing golden nematode in Quebec. Soil amendment with high rates of urea provided some reduction in populations but was not an economically viable option for managing potato cyst nematodes. Chicken manure and pig slurry did not provide a significant reduction of G. rostochiensis under Quebec field conditions.

Development and application of a multiplex qPCR method for the simultaneous detection and quantification of Pratylenchus alleni and P. penetrans in Quebec, Canada

Root lesion nematodes are very common plant-parasitic nematodes that affect a wide range of plants. More than one species can be found simultaneously in a field, and each has a different impact on crop yield. Unfortunately, identifying them using classical morphometric criteria is very difficult and time consuming. The species Pratylenchus alleni was recently observed for the first time in Canada, associated with severe damage in a soybean field in the province of Quebec. The major species, P. penetrans, is also known to be endemic in Quebec but no data exist on its distribution in field crops. This prompted the development of a multiplex quantitative polymerase chain reaction (PCR) assay for the simultaneous detection and quantification of P. alleni and P. penetrans. The method was found to be specific and sensitive, systematically detecting a single larva in a 100-cm3 soil sample with no cross-amplification with other species, even when they outnumbered the target species. An exogenous internal positive control was included in the test to avoid false negatives due to the presence of PCR inhibitors. This assay was used to study the distribution of P. alleni and P. penetrans in 185 soybean fields in the major soybean-producing areas of Quebec during a 3-year survey. Overall, P. penetrans was found in 42% of the fields, P. alleni in 8%, and both species in 4%. The population density of P. alleni in positive fields was still very low, with only a few larvae detected. However, densities of P. penetrans were much higher: the provincial mean was 51.7 nematodes per 100 cm3 of soil (in positive samples), and 8% of the fields (15 of 185) exceeded the theoretical economic threshold. The presence of P. penetrans was also strongly correlated with soil texture, with lighter soil being the most favorable.

A qRT-PCR method to evaluate viability of potato cyst nematode (Globodera spp.)

Abstract Potato cyst nematodes (PCN) – Globodera rostochiensis and G. pallida – cause significant yield losses on potato worldwide. One of the main challenges to PCN management is the ability of PCN to remain dormant in the soil for several decades. For that reason, many countries have strict quarantine regulations for PCN. These regulations, although expensive and restrictive for growers, are necessary to prevent further spread of PCN but should be lifted when no more viable cysts are found. Here, we report a promising qRT-PCR method for the quantification of viable eggs and propose that this method be included in routine testing. The method was successful for quantifying G. ellingtonae, G. rostochiensis and G. pallida and was found to be very sensitive with the systematic detection of a single larva. Intron-flanking probes were used to eliminate the possibility of false positives due to genomic DNA, and an internal control was added to detect failure in PCR due to inhibitors. No amplification occurred during the testing of eggs that had previously received heat treatments or fumigation with methyl bromide. This qRT-PCR assay was used to evaluate the viability of field populations of G. rostochiensis 10 years after the establishment of a quarantine area in Saint-Amable, Quebec, Canada. The number of viable eggs after a decade of regulation was found to be very low and confirmed the effectiveness of the measures put in place. Egg viability was also monitored in microplots following five continuous years of planting resistant potatoes, and no signs of resistance-breaking genotypes were observed.