Migração de Meloidogyne incognita para as Raizes de Soja In Vitro

The effects of timing of soybean seeding and the storage of second stage juveniles (J 2 ) of M. incognita on the migration and losses of body energy when J 2 were placed at the depth of 0, 2, 4 and 6 cm from soybean roots were studied. The J 2 were placed in glass tubes with sand and separated from the root by screen of 0.36 mm pore diameter before the soybean seeding. The tubes were stored for 5, 10, 15 or 20 days at 27 ± 2 °C. In another assay, the J 2 were placed in glass tubes at different distances and stored in sand for 5, 10, 15 or 20 days. The soybean was seeded after the storage period and the penetration assessment was done five days after the seeding. The interaction between inoculum distances and the evaluation periods and, also, between distances and the amount of J 2 lipids were not significant. However, the lipid amount of the non-infective J 2 decreased with the period of evaluation, reducing penetration of M. incognita. After 10 days from inoculation until the end of the assay, the number of M. incognita in the root was alike when the J 2 was placed at 4 or 6 cm from the soybean root, but 40 to 50 % lower than those placed at the soybean surface (0 cm) or at 2 cm from the root. When the J 2 were stored before seeding, penetration was reduced drastically after five days of storage, reducing to null after 10 days until the end of the assay. After five days of storage, the body lipid amount was 23 % of the original content, with lost of the infectiveness. Therefore, to evaluate migration of Meloidogyne J 2' the host must be present at the moment of the substract infestation.