Highlights  Detection and discrimination of plant stress origin using hyperspectral imaging.  Nematode infestation can be reliably differentiated from the water deficiency.  Abiotic drought resulted in the most obvious differences in the light spectrum.  Identification of nematode infestation possible with specific spectral regions.  Reliable prediction of nematode infestation even in early stages of infestation.

The tropical group of root-knot nematodes (RKN) including Meloidogyne ethiopica and M. luci is a highly polyphagus and damaging group of agricultural pests. M. ethiopica has been detected in several European countries (Slovenia, Italy, Greece) and also in Turkey. However, a description of a new sister species M. luci calls for reclassification of all European and Turkish M. ethiopica populations reported up to date as M. luci. Accurate identification can be accomplished through analysis of the esterase isozyme pattern, which is the most distinguishing character between the two otherwise very similar species. Both species display a three banded esterase pattern where the upper band is slightly shifted between the two species. In addition, molecular characterization of M. ethiopica and M. luci populations revealed that the ITS, SSU, and LSU of the rDNA regions are not appropriate markers for studying relationships among the tropical group of RKNs. However, the COII/lRNA region on mtDNA proved to be very useful for analyzing the phylogenetic relationship of these very closely related species/populations. Mitochondrial sequences with low levels of heteroplasmy allowed clustering of all M. luci populations in a monophyletic clade with a clear separation of this recently described species from M. ethiopica. At the same time, a very close relationship between M. ethiopica and M. luci was confirmed again.

Root-knot nematodes from the genus Meloidogyne are polyphagous plant endoparasites and agricultural pests of global importance. Here, we report the high-quality genome sequence of Meloidogyne luci population SI-Smartno V13. The resulting genome assembly of M. luci SI-Smartno V13 consists of 327 contigs, with an N50 contig length of 1,711,905 bp and a total assembly length of 209.16 Mb.

Although centromeres have conserved function, centromere-specific histone H3 (CenH3) and centromeric DNA evolve rapidly. The centromere drive model explains this phenomenon as a consequence of the conflict between fast-evolving DNA and CenH3, suggesting asymmetry in female meiosis as a crucial factor. We characterized evolution of the CenH3 protein in three closely related, polyploid mitotic parthenogenetic species of the Meloidogyne incognita group, and in the distantly related meiotic parthenogen Meloidogyne hapla. We identified duplication of the CenH3 gene in a putative sexual ancestral Meloidogyne. We found that one CenH3 (αCenH3) remained conserved in all extant species, including in distant Meloidogyne hapla, whereas the other evolved rapidly and under positive selection into four different CenH3 variants. This pattern of CenH3 evolution in Meloidogyne species suggests the subspecialization of CenH3s in ancestral sexual species. Immunofluorescence performed on mitotic Meloidogyne incognita revealed a dominant role of αCenH3 on its centromere, whereas the other CenH3s have lost their function in mitosis. The observed αCenH3 chromosome distribution disclosed cluster-like centromeric organization. The ChIP-Seq analysis revealed that in M. incognita αCenH3-associated DNA dominantly comprises tandem repeats, composed of divergent monomers which share a completely conserved 19-bp long box. Conserved αCenH3-associated DNA is also confirmed in the related mitotic Meloidogyne incognita group species suggesting preservation of both centromere protein and DNA constituents. We hypothesize that the absence of centromere drive in mitosis might allow for CenH3 and its associated DNA to achieve an equilibrium in which they can persist for long periods of time.

Meloidogyne ethiopica is a tropical rootknot nematode species which has recently been found in Europe. We examined its ability to survive in open fields located in regions with sub-Mediterranean and continental European climates. The outdoor microplot experiment consisted of two locations and lasted three growing and two winter seasons. It was demonstrated that M. ethiopica was able to survive at both locations and also that it retained its infection ability although temperatures below zero were recorded. The correct species was confirmed after each winter season by isozyme electrophoresis. Furthermore, the influence of temperature on the reproduction cycle of M. ethiopica was investigated. Meloidogyne ethiopica required 67, 48 and 36 days to complete the reproduction cycle at mean daily temperatures of 18.3, 22.7 and 26.3°C, respectively. At 13.9°C, M. ethiopica was not able to reproduce. The data obtained from these experiments were used to develop a correlation between temperature and the time needed for M. ethiopica to complete a reproduction cycle using a mathematical equation. Furthermore, eight vegetable crops that are important for agricultural production in Slovenia were tested for their suitability as hosts for M. ethiopica.