[Karyotypes of the stem eelworms from wild-growing plants]

Area of Science:

• Plant nematology
• Cytogenetics
• Evolutionary biology

Context:

• The species complex Ditylenchus dipsaci includes stem eelworms affecting various plants.
• Previous research focused on Ditylenchus dipsaci from cultivated hosts, noting a consistent chromosome number (n=12).
• Stem eelworms from wild plant species were less studied cytogenetically.

Purpose:

• To investigate the chromosomal characteristics of stem eelworms (Ditylenchus) parasitizing wild plants.
• To determine if stem eelworms from wild plants exhibit different chromosomal numbers compared to those from cultivated plants.
• To assess the taxonomic implications of observed chromosomal variations.

Summary:

• Stem eelworms collected from wild plants (Picris sp., Taraxacum officinale, Hieracium pratense, H. pilosella, Cirsium setosum, Falcaria vulgaris) exhibit significantly higher chromosome numbers, ranging from n=19 to n=28.
• In contrast, stem eelworms from cultivated plants consistently show a chromosome number of n=12.
• These findings indicate substantial cytogenetic divergence between populations from wild and cultivated hosts.

Impact:

• The study necessitates the separation of stem eelworm populations from wild plants from the collective species Ditylenchus dipsaci.
• It provides strong evidence that these distinct wild plant-associated forms represent separate species.
• The results suggest a polyploid origin for these distinct stem eelworm species, impacting our understanding of nematode speciation and evolution.