Vesicular-arbuscular mycorrhizae in field and pot grown Kiwifruit (Actinidia deliciosa).

Abstract

The presence of vesicular-arbuscular mycorrhizal (VAM) infection and spores was assessed in different periods of the year in the roots of field-grown kiwifruit (Actinidia deliciosa (A. Chev.ļ Liang & Ferguson) in Piedmont (NW Italy). Four fungal species were found in the kiwifruit orchards. Spore numbers were higher in spring and decreased in Summer; root colonization was generally high throughout the year. Kiwifruit seedlings were inoculated in pots with the VAM endo- phyte Glomus monosporum Gerd. T root colonization was reduced by P addition to the soil. Most cultivated species in the world are colonized in the field by vesicular-arbuscular mycorrhizal (VAM) fungi. The fungal mycelium penetrates host roots, form- ing intra and extracellular structures; the fungus may enhance plant growth, taking up nutrients from the soil and translocating them to the roots (Harley and Smith, 1983). Kiwifruit, a species native to Asia, was introduced in Italy in the early seventies, and orchards soon developed all over the country: plantations in 1984 covered an area of about 5,000 ha (Fraccaroli, 1986). However, no studies have been carried out in Italy so far on the pre- sence of mycorrhizae in this species and on their effects on plant growth. To gain preliminary knowledge of the mycorrhizal status of kiwifruit in Northern Italy we recorded the presence of VAM fungal species at different times of the year in kiwifruit plantations. Furthermore we inoculated plants in pots with a VAM endophyte to study the effect of mycorrhizae on the host growth in soils with a pro-