Learning from olive evolution and cultivation to understand the diversity of associated plant-parasitic nematodes communities in Morocco
Résumé
Plant-parasitic nematodes (PPN) significantly contribute to economic losses in the top-ten
olive producing countries, especially in the Mediterranean basin. Instead of controlling the
main pathogenic nematode species as usual, one innovative strategy to control PPN would be
to manage diversity in communities in order to lead them to be less pathogenic. Then,
knowing assemblage mechanisms in communities due to evolution and environmental forces
is a prerequisite. This study was conducted in Morocco, because (i) information about PPN
diversity is lacking, (ii) different forms of olive occur as wild (including two sub species O.
europaea subsp. europaea and subsp. Maroccana), feral and typical cropping systems as
traditional and high density and as irrigated or not) are present. Morphobiometric observations
revealed a very diverse parasite nematofauna (117 species), seven new taxa being recorded for
the first time on olive. Tylenchidae, Hoplolaimidae and Telotylenchidae nematodes were
dominant (80% of the samples), whereas root-knot nematodes (Meloidogyne spp.) were
detected in 40% of the samples. Multivariate analyzes showed that the development of
Heteroderidae and Longidoridae nematodes was favored in PPN communities on wild olive,
while lesion (Pratylenchidae) and root-knot nematodes multiply in orchards. Three
Meloidogyne species were identified: M. javanica on feral and cultivated olive in southern and
center Morocco; M. arenaria and M. hapla on wild olive in the north. Cytochrome oxidase I
(COI) and Internal transcribed spacer-2 (ITS2) genes were good markers for species
differentiation, but they were not able to distinguish M. javanica and M. arenaria populations
and were not adapted for intraspecific differentiation. However, a significant morphological
variability was observed between the Meloidogyne species, and within and between M.
javanica populations. The response of the diversity of PPN communities as well as of
Meloidogyne populations to olive genotype, geo-climatic zones and soil physico-chemical
characteristics, and diversity of plants associated with olive trees is discussed.
Domaines
Biodiversité et Ecologie
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