Arbuscular mycorrhizal fungi associated to Ochroma pyramidale (Cav. ex Lam.) Urb. (balsa) in the Ecuadorian Humid Tropic

Abstract

The objective of this investigation was to determine the genera of arbuscular mycorrhizal fungi (AMF) associated with Ochroma pyramidale (balsa) trees and their degree of root infection. Where studied six plantations of 1, 2, 3, 4, 5.5 and 7 years old, located in the central zone of the Ecuadorian Humid Tropic (EHT), in each of them three parcels of 500 m2 were delimited. From each plot, 3 soil samples (approximately 1 kg) and rootlets at a depth between 0 - 15 cm were collected to determine the percentage of mycorrhizal colonization. Isolation and identification of AMF at genus level and the estimation of mycorrhizal colonization was carried out by means of sieving methodology, wet decantation with centrifugation, and depigmentation – roots staining. Four genera of AMF were isolated and identified: Glomus, Acaulospora, Scutellospora, and Gigaspora, however, the genus Glomus predominated in the soil of all plantations. The populations were between 27 and 169 spores per 100 grams of dry soil. Four year old plantation contained he largest population, while other genera showed low representativeness in all ages. Low root mycorrhizal colonization was detected in the plantations balsa studied, with ranges from 0.28% to 0.65%, colonization rates lower than those reported for other woody species.