The use of in vitro mass multiplication of nematodes under axenic conditions allows intensification of studies on taxonomy, biology, epidemiology and control of these pathogens. In the present study, two methods were compared for in vitro multiplication of two species of plant-parasitic nematodes, Radopholus similis and Pratylenchus brachyurus in 20, 40 and 60 day-periods. Both techniques involved the use of carrot cylinders placed in jars with lids, with water-agar in the bottom of the flasks (WA+) or without (WA-). In WA- the nematodes were treated with a 1% solution of ampicillin whilst for WA+ the axenization was carried out with a solution of mercuric chloride (0.01%), and streptomycin sulfate 0.02%. The WA+ condition was the most favorable for multiplication of both species of nematodes, resulting in a population increase of about 280 times for R. similis and 226 times for P. brachyurus in relation to the founding population of 25 individuals. For WA- a population increase of only five times after 60 days for R. similis and a duplication of the population after 60 days for P. brachyurus was obtained. Overall, the largest amount of nematodes occurred at 60 days after inoculation.

Amostragens temporal (mensalmente em três campos por 12 meses) e espacial (uma vez, em 23 campos, de março a abril) foram feitas na principal região sojícola do Distrito Federal. Nos dois tipos de amostragem foram encontrados 53 gêneros de nematóides, sendo 13 deles detectados apenas pela temporal e um somente pela espacial. Do total, 53% foram fitoparasitos, 35% bacteriófagos e cerca de 12% micófagos, predadores e onívoros. Esses constituíram a comunidade de nematóides, dominada por Helicotylenchus (40% da abundância total), Acrobeles (15%), Cephalobus (7,6%), Meloidogyne (5,6%) e Pratylenchus (4,9%). Heterodera glycines não foi encontrado neste estudo. Não houve diferença quanto aos índices Ds, H', Es, T, FF/BF, (FF+BF)/PP, MI, PPI, mMI e Dorylaimida (%) entre as duas amostragens, mas houve diferença quanto aos índices d e J'. Os fitoparasitas tiveram populações reduzidas no final do ciclo da cultura, se mantiveram em nível baixo na estação seca e no período de desenvolvimento inicial das plantas, aumentando durante o crescimento das mesmas. Os micófagos se mantiveram em baixa população durante o ano, mas se elevaram em junho e julho, período de pós-colheita, em que raízes se encontravam em decomposição por fungos do solo. Os bacteriófagos tiveram suas populações ligeiramente reduzidas durante a seca e a fase inicial das chuvas, mas se elevaram no meio da estação chuvosa, estando, aparentemente, associadas à alta umidade do solo. Dentre os cinco gêneros mais abundantes, Acrobeles e Pratylenchus povoaram mais solos úmidos, enquanto Cephalobus e Meloidogyne adaptaram bem em solos secos, mas Helicotylenchus sobreviveu abundantamente numa grande faixa de umidade.

Temporal (monthly in three fields for 12 months) and spatial (once in 23 fields during March-April) samplings were conducted in the major soybean (Glycine max)-growing region of the Brazilian Federal District. Fifty-three nematode genera were found in both samplings, but 13 were detected only by the temporal sampling, and one only by the spatial sampling. Fifty-three percent were plant-parasites, 35% were bacterivores, and about 12% were fungivores, predators and omnivores constituted the community that was dominated by the genera Helicotylenchus (40% of total abundance), Acrobeles (15%), Cephalobus (7.6%), Meloidogyne(5.6%) and Pratylenchus (4.9%). Heterodera glycines was not found in this study. There were no differences in ten ecological measurements [Ds, H', Es, T, FF/BF, (FF+BF)/PP, MI, PPI, mMI, and Dorylaimida (%)] between the two sampling types, but differences in indexes d and J'. Plant parasite populations dropped at the end of the crop cycle, remained at low levels during the dry season and the seedling period, then increased again in the crop-growing season. Fungivores maintained their low populations throughout the year, increasing only in June and July, the post-harvest period, when soil fungi decomposed root tissue. The population of bacterivores slightly declined during the dry season and the initial rainy season, but peaked in the middle of the rainy season, apparently associated with soil humidity. In the five most abundant nematodes, those of Acrobeles and Pratylenchus were more populous in wet soils, Cephalobus and Meloidogyne adapted well in dry soils, but Helicotylenchus survived abundantly in a wide range of soil moisture.