The genetic architecture of host response reveals the importance of arbuscular mycorrhizae to maize cultivation

Abstract

Arbuscular mycorrhizal fungi (AMF) are ubiquitous in cultivated soils, forming symbiotic relationships with the roots of major crop species. Studies in controlled conditions have demonstrated the potential of AMF to enhance the growth of host plants. However, it is difficult to estimate the actual benefit in the field, not least because of the lack of suitable AMF-free controls. Here we implement a novel strategy using the selective incorporation of AMF-resistance into a genetic mapping population to evaluate maize response to AMF. We found AMF to account for about one-third of the grain production in a medium input field, as well as to affect the relative performance of different plant genotypes. Characterization of the genetic architecture of the host response indicated a trade-off between mycorrhizal dependence and benefit. We identified several QTL linked to host benefit, supporting the feasibility of breeding crops to maximize profit from symbiosis with AMF.

Conservation Agriculture Affects Grain and Nutrient Yields of Maize (Zea Mays L.) and Can Impact Food and Nutrition Security in Sub-Saharan Africa

“…Differences in root architecture between varieties and their level of root colonisation by symbiotic arbuscular mycorrhizal fungi may also justify the difference in their nutrient composition. In fact, mycorrhiza-associated maize plants showed higher grain yield ( 51 ) and enhanced proximate composition (crude protein, fat, moisture, and ash) of maize grain ( 52 ), but the importance of symbiotic fungi in the African context remains poorly understood. The reported information on maize grain composition of different varieties grown in Malawi in this study is an important resource to define nutrient yield baseline data in the Malawian context and encourage plant breeding efforts for nutritionally superior maize varieties.…”

Variation in mycorrhizal growth response among a spring wheat mapping population shows potential to breed for symbiotic benefit

“…Furthermore, if the root length colonised and the P benefit were tightly coupled, we might expect to have seen negative correlations between P content or concentration of shoots in non‐mycorrhizal plants and levels of AM fungal colonisation in the corresponding mycorrhizal group of the same lines, but these trends were not apparent (Figure S10a–d ). We suggest factors other than colonisation levels are likely to exhibit significant control over plant response to colonisation (Lefebvre, 2020 ; Ramírez‐Flores et al, 2020 ); focussing solely on maximising AM fungal colonisation is a potentially risky strategy to improve crop responsiveness. High levels of mycorrhizal colonisation may even elicit negative growth responses (Ryan et al, 2005 ; Tran et al, 2019 ).…”

Microbe-assisted crop improvement: a sustainable weapon to restore holobiont functionality and resilience

“…It will be important that future breeding strategies takes in account the interaction of root traits with symbiosis-related ones, with the aim to achieve optimal production also reducing application of fertilizers (mainly P-based products). An increasing number of studies report that AM responsiveness varies among plant accessions [ 161 , 162 ]. An important point that should be developed is related to the characterization of additional host genotypes, including landrace and wild-relative whose diversity should be more explored [ 163 ].…”