Arbuscular mycorrhiza in Colombian coffee plantations fertilized with coffee pulps as organic manure

The distribution of arbuscular mycorrhizal (AM) fungal structures in roots, in soil surrounding roots and in amended coffee pulps (CP) was investigated in 12 coffee plantations in Colombia. Fresh CP had been added to plants 6-10 months before sampling. The questions were whether soil chemical and physical parameter and soil depth had an effect on mycorrhiza. Root colonization rates with AM increased in CP amended-plants (F=7.75, P 0.05). External mycelium length differed between locations (F= 5.89, P< 0.001) and was inversely correlated with soil water content (r= -0.655, P= 0.02). External mycelium length per AM colonized root was higher in the lower soil layer (F=14.82, P< 0.05). Soil aeration seemed to be an important physical characteristic for mycorrhiza development in and around coffee roots. Higher mycorrhiza colonization in CP amended-plants might be an adaptive strategy for nutrients acquisition, and AM external mycelium that colonizes CP might take up nutrients directly during CP decomposition

Ambispora reticulata

A new glomeromycotean fungus,Ambispora reticulata, was found in the Swiss Alps and in the Chilean Andes. Only acauloambisporoid spores were detected so far, 87-131 x 125-150 μm in diameter and having a three-layered, yellow-brown to brown outer wall, a bi-layered, hyaline middle wall and a generally three-layered, hyaline inner wall. The middle wall has a characteristic reticulate outer surface with irregular triagonal to octagonal (usually tetrato hexagonal) pits that are surrounded by ridges. As known for all Ambispora species with acaulo-ambisporoid spore formation, the middle wall is a substantial part of the pedicel which connects the spore with the mycelium. The new species is a frequent member of arbuscular mycorrhizal fungal communities in mountainous and subalpine grasslands of the Swiss Alps at 1000-2100 m above sea level. It occurred less frequent in high alpine grasslands and at altitudes below 1000 m, where the fungus was found in a conservation tillage and a low-input tillage system. It was also detected in evergreen and in deciduous forests in the Andes of Southern Chile at elevations of 550-1600 m

Effect of seed treatment with natural products on early arbuscular mycorrhizal colonization of wheat by Claroideoglomus claroideum

Commercially available natural products (NP) were applied to seed of winter wheat which was sown in a sandy soil infected with the arbuscular mycorrhizal fungus Claroideoglomus claroideum. The aim was to investigate whether an isoflavonoid (formononetin), different humates/algae extracts and inorganics (dolomitic lime, silicates) improved the early mycorrhization process. Experiments were carried out under controlled conditions in small pots in in growth chambers. Plants were harvested between 14 and 29 days after treatment. The results showed that the isoflavonoid accelerated the mycorrhiza formation by increasing the number of mycorrhizal infection points with consequently higher infection frequency, intensity, and mycorrhized root biomass. A dolomitic limestone also improved the mycorrhizal infection process. No effects were found by the humates, extracts of algae and a silicate product. While in general the mycorrhization was most influenced by lower dose rates of NP (0.1 and 1 mg seed-1), a higher rate of 10 mg seed-1 had lower and sometimes negative effects on the mycorrhization. On the other side, highest NP doses had positive effects on some plant growth parameter, which may have been related to the potassium content of e.g. the humate products, or because these products had plant growth promoting effects. It can not be excluded that some products, like the dolomitic limestone had an indirect effect on the mycorrhiza development via influencing other micro-organisms in the wheat rhizosphere

Impact of long-term conventional and organic farming on the diversity of arbuscular mycorrhizal fungi

Previous work has shown considerably enhanced soil fertility in agroecosystems managed by organic farming as compared to conventional farming. Arbuscular mycorrhizal fungi (AMF) play a crucial role in nutrient acquisition and soil fertility. The objective of this study was to investigate the diversity of AMF in the context of a long-term study in which replicated field plots, at a single site in Central Europe, had been cultivated for 22years according to two "organic” and two "conventional” farming systems. In the 23rd year, the field plots, carrying an 18-month-old grass-clover stand, were examined in two ways with respect to AMF diversity. Firstly, AMF spores were isolated and morphologically identified from soil samples. The study revealed that the AMF spore abundance and species diversity was significantly higher in the organic than in the conventional systems. Furthermore, the AMF community differed in the conventional and organic systems: Glomus species were similarly abundant in all systems but spores of Acaulospora and Scutellospora species were more abundant in the organic systems. Secondly, the soils were used to establish AMF-trap cultures using a consortium of Plantago lanceolata, Trifolium pratense and Lolium perenne as host plants. The AMF spore community developing in the trap cultures differed: after 12months, two species of the Acaulosporaceae (A. paulinae and A. longula) were consistently found to account for a large part of the spore community in the trap cultures from the organic systems but were found rarely in the ones from the conventional systems. The findings show that some AMF species present in natural ecosystems are maintained under organic farming but severely depressed under conventional farming, indicating a potentially severe loss of ecosystem function under conventional farmin

La Micorriza: Un componente biotecnologico en la producción vegetal

El manejo de los recursos micorrizicos para favorecer la productividad de los cultivos no es una utopía, sino una biotecnología factible y al alcance de los investigadores colombianos

Influence of method of VA mycorrhizal inoculum placement on the spread of root infection in field-grown cassava

Three methods of placement of VA mycorrhiza inoculum to cassava were compared in the field in order to determine the effect of inoculation methodology on the spread of the introduced fungus in the soil. The spread of the indigenous fungi and of the introduced fungus, Glomus manihotis, with the roots was monitored at 3 soil depths and 3 distances from the planting stake, during 30 wk. of plant growth, corresponding to a cycle of rainy season-dry season- rainy season. In the dry season highest infection ratings were found in the deeper soil horizons; in the wet seasons they were higher in the surface soil. Placement of the inoculum under the stakes, or planting the stake in the inoculum band, increased root infection and the competitive ability of the introduced fungus in those zones where the inoculum was applied, especially during the 1st 3 mo. of growth. Best lateral spread of the introduced fungus was found with side banded inoculum, especially after the dry season. It is suggested that inoculum should be placed under the stakes at planting and reinoculated in side bands during or after the dry season in order to get best spread of the introduced fungusin the field. (AS