Soil properties and olive cultivar determine the structure and diversity of plant-parasitic nematode communities infesting olive orchards soils in southern Spain.

Juan E Palomares-Rius,Miguel Montes-Borrego,Blanca B Landa,Juan A Navas-Cortés,Pablo Castillo,Philippe Castagnone-Sereno

doi:10.1371/journal.pone.0116890

Juan E Palomares-Rius, Miguel Montes-Borrego + Show 4 more

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https://doi.org/10.1371/journal.pone.0116890

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Abstract

This work has studied for the first time the structure and diversity of plant-parasitic nematodes (PPNs) infesting olive orchard soils in a wide-region in Spain that included 92 locations. It aims at determining which agronomical or environmental factors associated to the olive orchards are the main drivers of the PPNs community structure and diversity. Classical morphological and morphometric identification methods were used to determine the frequency and densities of PPNs. Thirteen families, 34 genera and 77 species of PPNs were identified. The highest diversity was found in Helicotylenchus genus, with six species previously reported in Spain and with H. oleae being a first report. Neodolichorhynchus microphasmis and Diptenchus sp., Diphtherophora sp., and Discotylenchus sp., usually considered fungal feeders, were also reported for the first time associated to olive rhizosphere. PPNs abundance ranged from 66 to 16,288 individuals/500-cm3 of soil with Helicotylenchus digonicus being the most prevalent species, followed by Filenchus sp., Merlinius brevidens and Xiphinema pachtaicum. Nematode abundance and diversity indexes were influenced by olive cultivar, and orchard and soil management practices; while olive variety and soil texture were the main factors driving PPN community composition. Soil physicochemical properties and climatic characteristics most strongly associated to the PPN community composition included pH, sand content and exchangeable K, and maximum and minimum average temperature of the sampled locations. Our data suggests that there is a high diversity of PPNs associated to olive in Southern Spain that can exert different damage to olive roots depending on the olive variety and their abundance. Further analysis to determine the resistance levels of most common olive varieties to the prevalent PPNs in Spain will help to choose the most appropriate ones for the establishment of new plantations. This choice will take into consideration the specific soils and environments where those olive varieties will be established.

Highlights

And to the present times cultivated olive (Olea europaea L. subsp. europaea L.) has been culturally and economically very significant for the Mediterranean and Middle Eastern regions and remains integral to the economy of the Mediterranean area (e.g., Spain produces around 1/2 of the world production of olive oil, generating 1,886 million €) [1, 2]
Morphological and morphometric studies of diagnostic characters allowed the identification of 13 families, 34 genera and 77 species of plant-parasitic nematodes (PPNs) associated with olive orchard soils in southern Spain, including 10 species identified at genus level (Table 1)
The total number of PPNs in each orchard ranged from 66 to 16,288 individuals/500-cm3 soil and their percentage respect the total of PPNs in a sample ranged from 0.02% (Trichodorus giennensis) to 98.50% (Helicotylenchus digonicus)

Summary

Introduction

And to the present times cultivated olive (Olea europaea L. subsp. europaea L.) has been culturally and economically very significant for the Mediterranean and Middle Eastern regions and remains integral to the economy of the Mediterranean area (e.g., Spain produces around 1/2 of the world production of olive oil, generating 1,886 million €) [1, 2]. Europaea L.) has been culturally and economically very significant for the Mediterranean and Middle Eastern regions and remains integral to the economy of the Mediterranean area (e.g., Spain produces around 1/2 of the world production of olive oil, generating 1,886 million €) [1, 2]. Olive orchards cover about 10.2 M ha in the world, mainly in the Mediterranean Basin, of which more than 2.5 million ha of olives are located in Spain, mostly under rain fed production systems and 90% of them dedicated to oil production in 2012 [1, 3]. In Andalusia southern Spain, the cultivation of the olive under the guidelines of organic management has increased by 30% from 2006 to 2012, exceeding 54,800 ha of organic olive groves in 2012 [4], most of them (over 40%) being located in the province of Córdoba

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