Genetic control of arbuscular mycorrhizal colonization by Rhizophagus intraradices in Helianthus annuus (L.)

Plant symbiosis with arbuscular mycorrhizal (AM) fungi provides many
benefits, including increased nutrient uptake, drought tolerance, and
belowground pathogen resistance. To develop a better understanding of the
genetic architecture of mycorrhizal symbiosis, we conducted a genome-wide
association study (GWAS) of this plant-fungal interaction in cultivated
sunflower. A diversity panel of cultivated sunflower (Helianthus annuus
L.) was phenotyped for root colonization under inoculation with the AM
fungus Rhizophagus intraradices. Using a mixed linear model approach with
a high-density genetic map, we identified genomic regions that are likely
associated with R. intraradices colonization in sunflower. Additionally,
we used a set of twelve diverse lines to assess the effect that
inoculation with R. intraradices has on dried shoot biomass and
macronutrient uptake. Colonization amongst lines in the mapping panel
ranged from 0-70% and was not correlated with mycorrhizal growth response,
shoot phosphorus response, or shoot potassium response among the Core 12
lines. Association mapping yielded three single nucleotide polymorphisms
(SNPs) that were significantly associated with R. intraradices
colonization. This is the first study to use GWAS to identify genomic
regions associated with AM colonization in an Asterid eudicot species.
Three genes of interest identified from the regions containing these SNPs
are likely related to plant defense.