Rice flooding negatively impacts root branching and arbuscular mycorrhizal colonization, but not fungal viability.
Rice is mostly cultivated in wetlands, where arbuscular mycorrhization (AM) is reported to decrease. The mechanisms regulating such events are largely unknown. Rice uninoculated and inoculated with Rhizophagus irregularis were grown in dry and flooded conditions, allowing also for the transfer of plants from one water regime to the other. Roots were sampled at different times, from 7 to 35 d post-inoculation (dpi). The morphological and molecular parameters (root branching, aerenchyma formation, mycorrhizal colonization, AM marker gene expression) were evaluated. Root branching was more pronounced in dry conditions, and such phenotype was enhanced by the fungus. In wetlands, the colonization level was comparable till 21 dpi, when the mycorrhization then decreased, paralleled by an increase in aerenchyma. Expression of the fungal transporters was comparable under the two conditions. The root apparatus, when shifted from one water regime to the other, rapidly adapted to the new condition, revealing a marked plasticity. The reversibility of the AM rice symbiosis was also mirrored by expression changes of plant marker genes. The results demonstrate that the water regime is the driving force that regulates AM colonization under flooding conditions, by directly influencing root architecture and anatomy, but without impacting the basic AM functionality.
Institute for Plant Protection - National Research Council, Viale Mattioli 25, 10125, Turin, Italy.
Marta
M
Vallino
Valentina
V
Fiorilli
Paola
P
Bonfante
D015169:Colony Count, Microbial; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics; D050296:Microbial Viability; D038821:Mycorrhizae / Q000235:genetics / Q000254:growth & development*; D012275:Oryza / Q000378:metabolism / Q000382:microbiology* / Q000502:physiology*; D010641:Phenotype; D010710:Phosphates / Q000378:metabolism; D018520:Plant Shoots / Q000378:metabolism / Q000382:microbiology; D060888:Real-Time Polymerase Chain Reaction; D013997:Time Factors; D014867:Water / Q000502:physiology*
D010710:Phosphates; D014867:Water
arbuscular mycorrhizal symbiosis; gene expression; root system architecture; water regime