The nematicidal activity of saponins from Medicago arborea (tops), M. arabica (tops and roots) and M. sativa (tops and roots) against the plantparasitic nematode Xiphinema index was investigated. Nematicidal activity of related prosapogenins and sapogenins on X. index is also described. Saponins from Medicago spp. at different concentrations were all nematicidal, those from M. arborea tops being the less effective. In general, saponins induced 100% mortality at 500 μg ml −1 between 8 and 48 h, while prosapogenins resulted in toxicity starting at 125 μg ml −1 . Differences in the effects on X. index induced by prosapogenins and sapogenins were less pronounced, although prosapogenins displayed a larger range of activity. Assays with purified sapogenins demonstrated the relationship of the observed nematicidal activity of M. sativa and M. arborea to the content of the main aglycones (medicagenic acid and hederagenin, respectively) in the saponin extracts. Hederagenin displayed the highest bioactivity, giving 38% mortality after 1 h at 125 μg ml −1 .

Taxonomic keys and original descriptions were used to identify 26 Xiphinema americanum-group populations from Florida comprising X. georgianum (eight populations), X. citricolum (six), X. floridae (six), X. laevistriatum (five) and X. tarjanense (one). Principal component analysis of a subset of 19 morphometric characters accorded with the species designations; discriminant analysis of six characters assigned 93% (111 of 119) of the specimens to the correct putative species. A phylogeny of these populations estimated from analyses of rDNA sequences (ITS and D2D3) was also congruent with species designations from taxonomic keys and PCA. The D2D3 sequences revealed very little intraspecific variation whereas each population sampled produced a unique ITS sequence. Intraspecific variation in the suites of character code values from polytomous keys resulted mainly from minor discrepancies between population character means and reported character ranges for the species. We show that, for these taxa, species delimitation based on the requirement that sister taxa evolve autapomorphies distinguishes intraspecific variation from phylogeny and, as applied to molecular characters, delimits the same taxa as those predicted by morphological keys and PCA.

96 SummaryThe distribution of species of the Xiphinema americanumgroup in Hungary was studied by collecting 272 samples from 53 localities. Samples have been taken from soil in the rhizosphere of 70 plant species. In total, 12.86 % of the samples contained at least one species from the Xiphinema americanum-group. Three species were found: Xiphinema brevicollum, X. pachtaicum and X. simile. Xiphinema brevicollum occurred in 4.41 %, X. pachtaicum in 3.67 % and X. simile in 4.77 % of the samples. New data on plants associated with the reported species and developmental patterns for X. brevicollum and X. pachtaicum are also presented.

During a survey carried out in Serbia in October 1998 and 1999 a population of Longidorus was found in forest soil from Mt Goch (central Serbia). The population was identified as a new species and is described herein as Longidorus cylindricapitatus sp. n. The new species is characterised by a body length of ca 5.5 mm, a vulva located almost at the mid-body (V = 50.5), an almost cylindrical lip region, amphidial pouches more or less symmetrically bilobed, a very long odontostyle (164-178 µm), and conoid tail with a rounded terminus. Males were not found. Data for the four juvenile stages are presented.