Different farming and water regimes in Italian rice fields affect arbuscular mycorrhizal fungal soil communities

Abstract

Arbuscular mycorrhizal fungi (AMF) comprise one of the main components of soil microbiota in most agroecosystems. These obligate mutualistic symbionts colonize the roots of most plants, including crop plants. Many papers have indicated that different crop management practices could affect AMF communities and their root colonization. However, there is little knowledge available on the influence of conventional and low-input agriculture on root colonization and AMF molecular diversity in rice fields. Two different agroecosystems (continuous conventional high-input rice monocropping and organic farming with a five-year crop rotation) and two different water management regimes have been considered in this study. Both morphological and molecular analyses were performed. The soil mycorrhizal potential, estimated using clover trap cultures, was high and similar in the two agroecosystems. The diversity of the AMF community in the soil, calculated by means of PCR-RFLP (polymerase chain reaction-restriction fragment length polymorphism) and 18S rDNA sequencing on clover trap cultures roots, was higher for the organic cultivation. The rice roots cultivated in the conventional agrosystem or under permanent flooding showed no AMF colonization, while the rice plants grown under the organic agriculture system showed typical mycorrhization patterns. Considered together, our data suggest that a high-input cropping system and conventional flooding depress AMF colonization in rice roots and that organic managements could help maintain a higher diversity of AMF communities in soil.

Community Dynamics of Arbuscular Mycorrhizal Fungi in High-Input and Intensively Irrigated Rice Cultivation Systems

“…The presence of AMF in wetland ecosystems has received increased attention in recent years (7,9,32,33), but only a few field studies documenting AMF colonization have been conducted in paddy wetlands (2). In agreement with Watanarojanaporn et al (13), who reported that AMF are commonly present in rice roots from conventional paddy wetlands in Thailand, we found that AMF colonization in rice roots is commonly present at the heading and ripening stages though absent or rare at the early growth stages.…”

“…The AMF communities of some wetland habitats have been investigated (7,8,9,10,11), but whether AMF occur in paddy rice fields under waterlogged conditions is still under debate (12). Some studies found that AMF are able to survive in waterlogged paddy wetlands (13), but there are also reports showing that AMF are absent or rare due to the anoxic conditions that often prevail in waterlogged systems (2,14).AMF communities are not static within an ecosystem as the fungi are affected by changing biotic and abiotic factors (3). In order to gain insights into the functional role of AMF, it is important to obtain more knowledge on their distribution dynamics in different ecosystems.…”

“…A prerequisite for making this possible is the study of existing associations. It is widely accepted that the symbiotic arbuscular mycorrhizal fungi (AMF; phylum Glomeromycota) play a key role in sustainable production systems and that rice readily forms a symbiotic relationship with these fungi when it is grown in drained soils (i.e., upland conditions) (2). AMF form symbiotic relationships with most terrestrial plants, including many crop plants.…”

Isolation and Identification of Arbuscular Mycorrhizal Fungi from Agricultural Fields of Vietnam

“…The genus Acaulospora, generally is not frequent in the arable lands [20,26], because not disturbance tolerant. In our work it appeared o be well represented, also in a par- ticular condition like rice grown in flooding regime, where members of the family Glomeraceae (Funneliformis, Rhizophagus ...) were expected [22]. The uncultured Acaulospora sequence phylogenetically related to RP2 was obtained in an unpublished study on rice cultivation in Thailand.…”

“…These data could find an explanation in the flooding regime the crop was subjected to. As reported in several publications flooding has a negative impact both on root colonization and spore abundance in the soil, probably to the anoxic environment [21,22]. Other studies showed that AMF can colonize roots of aquatic plants depending on the affiliation to monocots or dicots species [23].…”