Mycorrhizal colonization in bread wheat varieties differing in their response to phosphorus

Abstract

Arbuscular mycorrhizal fungi (AMF) play an important role in phosphorus (P) nutrition of plants. Varietal differences in AMF infection occur but there is limited information on the importance of these differences to P efficiency in wheat. This work was conducted to determine whether variation in AMF infection could help explain genetic differences in responses to P. Ten wheat varieties that vary in their grain yield response to P were compared at different rates of P in two controlled environment experiments. Plant samples were also collected from a field experiment with two P rates. Significant genetic variation was observed for AMF colonization in all experiments, but these differences were not consistently related to the yield responsiveness to P among the ten varieties. Two varieties, Carazinho and RAC875 that have a low yield response to P, had consistently high root colonization while a P-responsive variety, Wyalkatchem, had low root colonization. Adding P fertilizer reduced AMF colonization and at high P rates negative associations between AMF colonization and seedling growth and P uptake were observed among the varieties. Among some varieties, their grain yield response to P and P efficiency were consistent with their AMF colonization. However, the negative effect of mycorrhizal infection on seedling growth at high soil P suggests AMF colonization may only be a suitable trait for improved P efficiency in farming systems where available P is consistently low.