Based on reading
Sorghum, both in raw form, Syrup Extract, and Syrup itself. The syrup extract is the closest thing to barley in terms of FAN, enzymes, and sugar content, but imparts a tangy, bitter, or citrusy aftertaste.
You could get away with brewing a Hoegaarden style beer us WB-06 and some Citrus Zest and corriander