Fig. 1: Effects of fatty acid salts and organic nitrogen sources on asymbiotic cultures of R. clarus.

a Effects of potassium myristate (Myr-K) and peptone (Pep) on R. clarus growth. AM fungi were incubated in a medium with or without 100 μM Myr-K and 0.2 g l⁻¹ peptone for 6 weeks. Branched hyphae (blue arrows) were observed around a parent spore (yellow arrowhead) in a medium containing Myr-K. Small, white spores were formed among densely packed coils (DPCs, outlined arrowheads) in a medium containing both Myr-K and Pep. The rightmost picture is a magnified image of the dotted box in the middle picture. Pink arrowheads indicate newly generated secondary spores. Pink arrows indicate runner hyphae. Bars = 500 µm. b Sporulation rates, percentage of secondary spore-forming parent spores relative to germinated parent spores, in cultures supplemented with 100 μM fatty acid at 6 weeks after incubation (WAI). Three bars in each condition are trials 1–3, respectively, from the left. 2OH-TDA 2-hydroxytetradecanoic acid. C14:0-K potassium myristate. C16:0-K potassium palmitate. C16:1Δ9Z-K potassium palmitoleate. c Sporulation rates in cultures with 0.2 g l⁻¹ organic nitrogen source in the presence of Myr-K at 6 WAI. Different letters above of the graph indicate significant differences among treatments in each trial using Fisher’s exact test with Bonferroni correction (p < 0.05). Malt, malt extract. SC, SC dropout. Yeast, yeast extract. d Numbers of secondary spores generated from a single parent spore in medium supplemented with each organic nitrogen in the presence of Myr-K at 6 WAI. Diamonds indicate medians. Statistical significance was calculated using the Wilcoxon rank-sum test with Bonferroni correction. Different letters indicate significant differences (p < 0.05). p-values are described in Supplementary Data 2.