By Scott Alarik, Globe Correspondent  |  June 4, 2010

At first glance, it’s hard to see what connects the dizzyingly diverse acts at Sunday’s Boston Music Festival on the UMass-Boston campus in Dorchester. The lineup merrily spans genres and generations, with ’60s superstar John Sebastian and hot young Canadian folk-popsters Dala; guitar legend David Bromberg and avant-folk songwriter Anais Mitchell; searing roots-rocker Les Sampou and Gandalf Murphy & the Slambovian Circus of Dreams, with their self-described “punk-classical-hillbilly-Floyd.’’

But two crucial threads bind them together. First, they all fit under the vast canopy of modern folk music, which isn’t surprising, since the country’s only full-time folk station, WUMB-FM (91.9), is producing the festival. Second, it’s unlikely that any of these careers could exist without public stations like WUMB.

As Lovin’ Spoonful founder and leading light of the ’70s songwriter movement, Sebastian has had lots of mainstream airplay. But recent rootsy forays with his jug band, and an acclaimed collaboration with Dawg-grass icon David Grisman, were heard almost exclusively on public radio.