Artículos científicos

A new fungal species of the Glomeromycetes, Acaulospora aspera, was isolated from the rhizosphere of the inka nut (Plukenetia volubilis) in San Martín State of Peru (Western Amazonia) and propagated in bait cultures on Sorghum spp., Brachiaria brizantha, Medicago sativa and P. volubilis as host plants. The fungus forms brownish yellow to yellow brown spores, (120-)135-195 × (120-)130 187 μm in diameter. The surface of the structural spore wall layer is crowded with small depressions, 0.4-0.7 μm in diameter, up to 0.8 μm deep, and only 1.1-1.8 apart, giving the spore surface a rough, washboardlike appearance, especially when the outermost, evanescent wall layer has disappeared. Phylogenetically, the new species is close to A. spinosissima, A. excavata and to other morphologically more similar species such as A. spinosa and A. tuberculata, which form spiny or tuberculate projections on the outermost, semi-persistent spore wall layer, or A. herrerae, A. kentinensis, A. scrobiculata and A. minuta, which on the structural spore wall layer all have more pronunced pits than A. aspera. In this study, also the name of A. spinosissima was validated, as it had been preliminary declared invalid because of a typing error in the diagnosis section of its original description.

A new arbuscular mycorrhizal fungus, Acaulospora flava, was found in coffee (Coffea arabica) and inka nut (Plukenetia volubilis) plantations in the Amazonia region of San Martín State in Peru. The fungus was propagated in bait cultures on Sorghum vulgare, Brachiaria brizantha and Medicago sativa as host plants. It differentiates typical acaulosporoid spores laterally on sporiferous saccule necks. The spores are light yellow, bright yellow to yellow brown, (95-)105-160 × (95-)100-150 μm in diameter and have smooth spore surfaces. Phylogenetically, A. flava clusters in a well-separated clade, nearest to A. kentinensis, followed by A. herrerae, A. spinosissima, A. excavata and A. aspera, of which remarkably A. spinosissima, A. excavata and A. aspera had also been found in inka nut plantations of San Martín State during the last years. Here, we report also A. herrerae and A. fragilissima as fungal symbionts within the rhizosphere of coffee and the inka nut. The later two fungi had so far been recorded by concomitant morphological and molecular analyses only from tropical islands, A. herrerae from Cuba in the Golf of Mexico and A. fragilissima from New Caledonia in the southwest Pacific Ocean close to Australia. In this study, the ITS region of A. herrerae was analyzed for the first time and deposited in the public databases. In total, we already recovered fourteen Acaulospora species from coffee and inka nut plantations in San Martín State of Peru, suggesting that Acaulospora species are frequent and beneficial symbionts in coffee and inka nut roots in San Martín State of Peru.