Distribution of Meloidogyne chitwoodi in potato tubers and comparison of extraction methods
Meloidogyne chitwoodi and M. fallax are quarantine organisms in Europe. One measure to restrict the spread of these nematodes is careful inspection of potato tubers. The distribution of M. chitwoodi in heavily infected tubers was studied and several methods for extraction of these nematodes from tubers were compared. The majority of the nematodes (96%) were found in the first 5.25 mm of the tuber, corresponding to the depth of the vascular ring. About half of them were found between 1.75 and 3.50 mm deep. Incubation of small pieces of tuber on Baermann funnels in the misting chamber during 36 days yielded about 12 times fewer juveniles than mixing potato tissues and extracting them using zonal centrifugation, a process that took about 1 h. Enzymatic maceration of potato tissues for 24 or 48 h did not liberate more nematodes than 2 min of blending the tissues at high speed. More nematodes, with 95% consisting of eggs, were extracted by zonal centrifuging than by pouring the macerated suspension over a set of 500 μm, 250 μm and 20 μm sieves.