Land Snail Assemblages of Olive Orchards in Crete, Greece

Land snail biodiversity research in agroecosystems is limited, if non-existent. Here we investigate the land snail assemblages of olive orchards in Messara plain, Crete, Greece. Land snails were collected from 16 olive orchards. In addition, we performed a literature survey and recorded all species reported in the surrounding area. We found 18 species in the olive orchards among the 37 species found in the area and reported in the literature. Xerotricha conspurcata (Draparnaud, 1801) and Caracollina lenticula (Michaud, 1831) are reported for the first time in the study area. Their presence is probably a result of human-mediated dispersal. Olive orchards proved to be an important refuge for land snail diversity as they host 43% of the species found in the surrounding area. We highlight the importance of olive orchards as habitats with increased land snail richness. We suggest that land snails should be included in future biodiversity research in agricultural areas

Effect of Different Cover Crops on Suppression of the Weed Oxalis pes-caprae L., Soil Nutrient Availability, and the Performance of Table Olive Trees ‘Kalamon’ cv. in Crete, Greece

Winter cover crops are used in organic olive production to increase N-supply and yields, and to reduce weed competition. However, there is limited information on the effect of different cover crops on weed suppression, soil fertility and productivity of organic olive orchards. Here, we compared the relative effect of four contrasting cover crops established from (i) untreated vetch seed, (ii) vetch seed inoculated with a commercial Rhizobium seed inoculum, (iii) an untreated vetch/barley/pea seed mixture and (iv) untreated seed of Medicago polymorpha L. (a native legume species which establishes naturally in olive orchards in Crete) in a 35-year-old experimental table olive orchard. The use of a vetch/barley/pea mixture resulted in the greatest suppression of the dominant weed species Oxalis pes-caprae. Rhizobium inoculation of vetch seed resulted in significantly lower vetch establishment and significantly higher Oxalis suppression but had no significant effect on the root nodulation of vetch plants. There was no significant difference in fruit yield between cover crop treatments, but the fruit weight was significantly higher when cover crops were established from un-treated vetch seeds and the vetch/barley/pea seed mixture compared with the cover crops based on inoculated vetch or Medicago seed. However, although Medicago establishment was very low (<10 plants/m2), fruit yields were numerically 20% higher in the Medicago plots. These findings suggests that, overall, legume cover crops had no effect on fruit yields. This conclusion is supported by the results of the olive leaf analyses which detected no significant differences in nitrogen and other mineral macro- and micronutrient concentration between treatments, except for B (highest in olive leaves from Medicago and lowest in untreated vetch plots) and Mo (highest in olive leaves from Medicago and lowest in vetch/barley/pea mixture plots). Overall, our results suggest that the current recommendation to establish legume-based cover crops in organic olive orchards every year, may need to be revised and that establishing cover crops every 2–4 years may reduce costs without affecting olive fruit yields

Integrative diagnosis and molecular phylogeny of dagger and needle nematodes of olives and grapevines in the island of Crete, Greece, with description of Xiphinema cretense n. sp. (Nematoda, Longidoridae)

The occurrence and geographic distribution of longidorid nematode species inhabiting the rhizosphere of cultivated and wild olive and grapevine in Crete Island were investigated. Morphological and morphometrical studies identified five Longidorus and six Xiphinema species, with frequencies of prevalence (for wild and cultivated olives and grapevines, respectively) as follows: Longidorus closelongatus (2.0–13.3 %), L. cretensis (1.0–6.7 %), L. moesicus (13.3 % only in grapevines), L. orientalis (3.3 % only in grapevines), L. pseudoelongatus (7.0 % only in olives), Xiphinema cretense n. sp. (3.0 % only in olives), X. index (3.0–23.3 %), X. israeliae (6.3 % only in olives), X. italiae (3.3–10.0 %), X. pachtaicum (26.7–42 %) and X. simile (3.3 % only in grapevines). Xiphinema cretense n. sp. is characterized by a body size 3,872–6,135 μm long, lip region anteriorly rounded, separated from the rest of the body by a depression, odontostyle and odontophore 140.6 and 80.3 μm long respectively, vulva position at 46.0–50.5 %, female tail 31.0–38.0 μm long, nearly hemispherical with curvature essentially dorsal and with a tip completely rounded or presenting a very short bulge, c ratio (119.1–186.9), c’ ratio (0.7–0.8). Molecular characterisation using D2-D3 expansion regions of 28S rRNA, 18S rRNA and ITS1-rRNA was carried out and maximum likelihood and Bayesian inference analysis were used to reconstruct phylogenetic relationships among these species and with other longidorids.This research was supported by grant KBBE 219262 ArimNET-ERANET FP7 2012–2015 Project PESTOLIVE ‘Contribution of olive history for the management of soilborne parasites in the Mediterranean basin’ from Hellenic Agricultural Organization-DEMETER and Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), grant AGR-136 from ‘Consejería de Economía, Innvovación y Ciencia’ from Junta de Andalucía, and Union Europea, Fondo Europeo de Desarrollo regional, “Una manera de hacer Europa”. E. Nasiou and M.S. Lazanaki are employed by the ARIMNET-PESTOLIVE project. The seventh author is a recipient of a “Juan de La Cierva” contract from Ministerio de Economía y Competitividad of Spain.Peer Reviewe