Survival and development of potato psyllid
(Hemiptera: Triozidae) on Convolvulaceae:
Effects of a plant-fungus symbiosis

This one mentions species that have Periglandula but contain no alkaloid, like Convolvulus equitans. Some of the early works on the symbiote try to confirm it via the presence of Ergot alkaloids, however by looking for the DNA of the symbiote it was found that some plants can have the symbiote and lack alkaloids.