Flint maize root mycorrhization and organic acid exudates under phosphorus deficiency: Trends in breeding lines and doubled haploid lines from landraces

Abstract

Aims: High maize yields in modern well-managed agroecosystems depend on the use of elite varieties and hybrids. Unfortunately, because of repeated selection at high fertilizer rates, some beneficial traits, such as the interaction with arbuscular mycorrhizal fungi or the release of organic acid anions for phosphate mobilization and for attracting beneficial microorganisms, might be gradually declining in modern elite genotypes. However, old founder lines and landraces possibly carry genetic relicts that originate from pre-green revolution times that are useful for breeding elite material for low input farming systems. Methods: Seedling colonization with arbuscular mycorrhizal fungi (AMF) and organic acid anion release were measured in flint lines that were released over more than five decades ago and in six preselected doubled haploid (DH) lines from landraces. P-uptake-related root traits were compared under P-sufficient and P-deficient conditions. Results: Weak trends for the loss of AMF colonization or changes in organic acid anion release at low P supply were detected in modern varieties. One DH line from a landrace was found with increased mycorrhization, whereas others were similar to modern elite lines. Overall, substantial genetic variance was encountered for these traits. Conclusions: The concern that modern elite maize varieties have lost beneficial traits for nutrient acquisition is not substantiated for the flint pool of maize, although weak trends exist. Lines associated with better P-acquisition efficiency under limited P availability should be utilized for breeding more sustainable varieties.