Global warming and distribution of root-knot nematode species of the tropical group (MeloTrop)
Širca, Saša; Gerič Stare, Barbara; Strajnar, Polona; Knapič, Matej; Žibrat, Uroš; Folcher, Laurent; Ollivier, Fabrice; Buisson, Alain; Chappe, Anne-Marie; Inacio, Maria Lurdes; Rusinque, Leidy; Nóbrega, Filomena; de Andrade, Eugenia; Karseen, Gerrit; van Hesse, Evelyn; Warbroek, Tim; Abrantes, Isabel L.P.M; Conceição, Isabel; Maleita, Carla; Bacic, Jasmina
Root-knot nematodes (RKN) (Meloidogyne spp.) represent a relatively small but economically important group of obligate plant parasites. Several RKN species belong to the ‘tropical’ RKN group which can cause significant economic losses in agriculture, especially in vegetable crops. The species of this group reproduce by mitotic parthenogenesis and are pests of important food crops, vegetables, fruits and ornamentals grown in tropical, subtropical and temperate climates. The damage and yield losses caused by this group are greater in tropical regions than in temperate regions because of more favourable environmental conditions for pest colonization, development, reproduction and dispersal. However, climate change will influence the spread of these pests and their dispersal across temperate regions.
The project aimed to organise surveys in several partnering countries to map the occurrence and distribution of tropical RKN species, to validate biochemical and/ or molecular diagnostic tests and to study the survival ability of RKN species at the open field conditions in the continental climate and Mediterranean/ Atlantic conditions.
Data on the distribution of tropical RKN species in partner countries were obtained focussing on sites of field cultivation and ornamental production and by summing national record data on the occurrence of tropical RKN. In total, 107 locations from France, Portugal, Serbia and Slovenia were covered. The most frequently identified species was Meloidogyne incognita, recorded at 47 locations. The second most common species was M. arenaria (21 locations), followed by M. javanica (11 locations), M. hispanica (7 locations), M. luci (6 locations) and of M. enterolobii (2 locations). Mixed species were also found at 13 sites. Forty-three different host species were recorded. Tropical RKN species in the open areas was predominantly distributed in areas with Mediterranean climatic conditions, but a small proportion of sites were recorded in areas with semi-continental climates and mild winter conditions.
Five laboratories from partner institutions participated in the test performance study to identify RKN species using biochemical and molecular tests. For isozyme phenotyping, the average agreement of results was 85.1%, while successful identification among laboratories ranged from 58.3 to 100%. Not all species were identified with the same success. The species that were correctly identified 100% of the time were M. arenaria and M. enterolobii. For M. hispanica, M. javanica and M. luci, 90% agreement was achieved, while 80% for M. incognita, 70% for M. ethiopica and 60% for M. inornata. A modified DNA barcoding method, in which four mtDNA coding regions were sequenced, did not prove to be a successful method for identifying all eight selected species. Only 36% of the samples were correctly identified by all laboratories involved in the test performance study. Sequencing of additional mtDNA regions as well as having valid reference data for more species in public nucleotide sequences databases (e.g. Genbank, ENA, Q-bank) could achieve better resolution and correct species identification, but the success rate of identification among laboratories remains to be tested.
The survival ability of M. incognita and M. arenaria in the field under continental climatic conditions was studied. Both species survived and maintained their infectivity in a micro-plot (semi-field conditions) filled with soil during three consecutive winters at the Ljubljana site, defined as continental conditions. The potential suitability of European territory for survival and development of selected tropical RKN species was assessed with CLIMEX software and simulation of the influences of climate change scenario were performed.