Wheat root trait plasticity, nutrient acquisition and growth responses are dependent on specific arbuscular mycorrhizal fungus and plant genotype interactions

This study aimed to examine how interactions at both plant genotype and arbuscular mycorrhizal fungus species levels affected the expression of root traits and the subsequent effect on plant nutrition and growth. We used two wheat cultivars with contrasting phosphorus (P) acquisition efficiencies (Tukan and Crac) and two arbuscular mycorrhizal (AM) fungi (Rhizophagus intraradices and Claroideoglomus claroideum). Plant growth, as well as morphological and architectural root traits, were highly dependent on the myco-symbiotic partner in the case of the less P-acquisition efficient cultivar Tukan, with mycorrhizal responses ranging from -45 to 54 % with respect to non-mycorrhizal plants. Meanwhile, these responses were between only -7 and 5 % in the P-acquisition efficient cultivar Crac. The AM fungal species produced contrasting mechanisms in the improvement of plant nutrition and root trait responses. Colonization by R. intraradices increased Ca accumulation, regardless of the cultivar, but reduced root growth on Tukan plants. On the other hand, C. claroideum increased P content in both cultivars, with a concomitant increase in root growth and diffusion-based nutrient acquisition by Tukan. Moreover, plants in symbiosis with R. intraradices showed greater organic acid concentration in their rhizosphere compared to C. claroideum-colonized plants, especially Tukan (24 and 35 % more citrate and oxalate, respectively). Our results suggest that the responses in plant-AM fungal interactions related to nutrient dynamics are highly influenced at the fungus level and also by intra-specific variations in root traits at the genotype level, while growth responses related to improved nutrition depend on plant intrinsic acquisition efficiency.

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