Abstract
Root-knot nematodes of the genus Meloidogyne are recognised worldwide as a major production constraint in crops of primary economic importance. Knowledge of their diversity and prevalence, as well as the major environmental and agronomical cues for understanding their distribution in specific areas is of vital importance for designing control measures to reduce significant damage. We provide the first detailed information on the diversity, distribution and levels of Meloidogyne species infecting wild and cultivated olive soils in a wide-region in southern Spain that included 499 sampling sites. Overall Meloidogyne spp. were found in 6.6% of sampled olive plants, with 6.6% and 6.5% for cultivated and wild olive, respectively. We identified five previously described Meloidogyne spp. (Meloidogyne arenaria, M. baetica, M. hapla, M. incognita, M. javanica) and one new species (Meloidogyne oleae sp. nov.) which, characterized using integrative taxonomy, increases the known biodiversity of Meloidogyne spp. affecting olive. Meloidogyne arenaria and M. incognita were only found infecting cultivated olive varieties, while, M. baetica was only found infecting wild olive. Three major parameters drive the distribution of Meloidogyne spp. in cultivated olives in southern Spain, cover vegetation on alley, irrigation and soil texture, but different species respond differently to them. In particular the presence of M. incognita is highly correlated with sandy loamy soils, the presence of M. javanica with irrigated soils and cover vegetation, while the presence of M. arenaria is correlated with the absence of cover vegetation on alley and absence of irrigation. These parameters likely influence the selection of each particular Meloidogyne species from a major dispersal source, such as the rooted plantlets used to establish the orchards.
Highlights
Root-knot nematodes (RKN) of the genus Meloidogyne Goeldi, 1892 [1] are recognised worldwide as one of the major production constraints of crops of primary economic importance, including vegetables, fruit-crops, ornamental and wild plants [2]
Our research aims were: i) to survey and identify the Meloidogyne spp. populations detected in wild and cultivated olives; ii) to carry out a molecular characterisation of these Meloidogyne populations based on sequences of the D2-D3 expansion segments of the 28S nuclear ribosomal RNA gene, the ITS1 of rRNA, partial 18S rRNA, partial cytochrome oxidase subunit II (coxII)-16S sequences and coxI; iii) to describe a new species Meloidogyne oleae n. sp. parasitizing wild and cultivated olives which was discovered during the species identification; iv) to study the phylogenetic relationships of Meloidogyne spp.; and v) to determine environmental patterns structuring the species composition of RKNs infecting cultivated olives in southern Spain
M. arenaria and M. incognita were found only in cultivated olive, whereas the rest of species, M. oleae sp. nov., M. hapla and M. javanica could be found in both types of olive trees
Summary
Root-knot nematodes (RKN) of the genus Meloidogyne Goeldi, 1892 [1] are recognised worldwide as one of the major production constraints of crops of primary economic importance, including vegetables, fruit-crops, ornamental and wild plants [2]. The application of molecular methods to studies of RKN and systematics has revealed that some long-assumed single species are cryptic species that are morphologically indistinguishable but may be phylogenetically distant to one another [8]. For these reasons, the integration of molecular and isozyme electrophoretic pattern techniques with classical morphological approaches should help to provide tools for differentiating Meloidogyne species and significantly improve and facilitate the routine identification of these nematodes
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