Root cortical anatomy is associated with differential pathogenic and symbiotic fungal colonization in maize

Abstract

Root anatomical phenotypes vary among maize (Zea mays) cultivars and may have adaptive value by modifying the metabolic cost of soil exploration. However, the microbial trade‐offs of these phenotypes are unknown. We hypothesized that nodal roots of maize with contrasting cortical anatomy have different patterns of mutualistic and pathogenic fungal colonization. Arbuscular mycorrhizal colonization in the field and mesocosms, root rots in the field, and Fusarium verticillioides colonization in mesocosms were evaluated in maize genotypes with contrasting root cortical anatomy. Increased aerenchyma and decreased living cortical area were associated with decreased mycorrhizal colonization in mesocosm and field experiments with inbred genotypes. In contrast, mycorrhizal colonization of hybrids increased with larger aerenchyma lacunae; this increase coincided with larger root diameters of hybrid roots. F. verticillioides colonization was inversely correlated with living cortical area in mesocosm‐grown inbreds, and no relation was found between root rots and living cortical area or aerenchyma in field‐grown hybrids. Root rots were positively correlated with cortical cell file number and inversely correlated with cortical cell size. Mycorrhizae and root rots were inversely correlated in field‐grown hybrids. We conclude that root anatomy is associated with differential effects on pathogens and mycorrhizal colonization of nodal roots in maize.

Impacts of directed evolution and soil management legacy on the maize rhizobiome

“…Improve-ment of aboveground traits during maize evolution had unintended belowground effects that likely impacted rhizosphere interactions. For example, both domestication and agricultural intensification affected maize root system architecture, which can affect rhizobiome composi-tion (Corneo et al, 2016), and anatomy, which can affect pathogenic and symbiotic fungal colonization (Galindo-Castan~eda et al, 2019). Domestication led to longer nodal roots, more seminal roots, more aerenchyma, and greater genetic variation for anatomical and archi-tectural traits in landraces than teosinte (Burton et al, 2013), and reduced root branching despite equivalent root:shoot ratio (Gaudin et al, 2014).…”

Polyploidy and plant-fungus symbiosis: evidence of cytotype-specific microbiomes in the halophyteSalicornia(Amaranthaceae)

“…For example, Forrester et al (2020) noted a greater generalization in bacterial assemblages in autotetraploid individuals of Medicago sativa compared to diploids, suggesting that larger cells in polyploids could host a greater quantity of different bacterial symbionts, compared to smaller cells in diploids. In the case of fungi, Galindo-Castañeda et al (2019) reported a decrease in mycorrhizal colonization in Zea mays with a decrease in the living cortical area. In the case of Salicornia , our anatomical data showed no differences in cell size between the two cytotypes (Table 1).…”

“…The two species have a similar morphology and react highly plastic to changes in the environment, which makes morphology-based species identification challenging and time-consuming. In addition to that, there are no studies investigating whether the two cytotypes differ in root anatomical traits, which could directly influence fungal recruitment and community establishment, as observed for endophytic bacteria (Forrester et al 2020) and fungi (Galindo-Castañeda et al 2019). Because of the morphological similarities of the cytotypes, species identification is mostly conducted based on their differences in ploidy (Kadereit et al 2007).…”

Improving Soil Resource Uptake by Plants Through Capitalizing on Synergies Between Root Architecture and Anatomy and Root-Associated Microorganisms

“…As discussed below, root anatomical phenotypes could be important drivers of root and rhizosphere microbiomes, as well as other root-associated biota including nematodes and insects ( Lynch et al, 2021 ). For example, root cortical anatomy in maize is associated with differential effects on root colonization by Fusarium species and beneficial mycorrhizal fungi ( Galindo-Castañeda et al, 2019 ).…”