Nematodes and nematophagous fungi associated with Citrus fields and Pinus halepensis-Quercus rotundifolia forest soil

Abstract

Eight forest (Quercus rotundz/olia and Pinus halepensis) and seven crop field (Citrus spp.) soils were surveyed in southeast Spain for nematode and nematophagous fungi. Nematodes were markedly more abundant in forest than in Citrus soils. The most commonly occurring group of nematodes were free-living nematodes (especially Rhabditis spp.) which occurred in both soil types. The mostly prevalent plant parasitic genera, which occurred in both soil types, were Filenehus sp., Aphelenehus sp. and Pratylenehus sp. Predatory nematodes (Mononchidae) were also found in the forest soil. The nematophagous fungi detected depended on the technique used. Only predatory fungi were found using the soil sprinkling technique and of these Arthrobotrys oligospora var. oligospora (adhesive network former) was the most frequent species (ca. 50% soil samples). A. javaniea, A. arthrobotryoides, A. oligospora var. mierospora, A. oligospora var. sarmatiea, A. musz/ormis and A. broehopaga (constricting rings) were less frequently found. Monaerosporium sp. (bidimensional adhesive network) was found in both Citrus and forest soils. Predatory nematophagous fungi appeared earlier and in higher numbers in Citrus than in forest soils. The most common endoparasitic fungus was Catenaria anguillulae (ca. 80% soil samples) followed by Myzoeytium sp. Nematoetonus con currens was also found infecting nematodes. Our data show that the mediterranean soils studied acted as an important reservoir for a diverse range of nematophagus fungi which utilised different modes of action to attack nematodes and that some of these nematophagous fungi could have the potential to be developed as biocontrol agents of plant-parasitic nematodes.