There is a deep connection between the banjo and the blues, but this influence was no doubt exhibited in different ways in different parts of the country. The fiddle and the banjo were the most popular instruments in African American life from practically the earliest forced importation to the early 20th century - a span of almost 250-300 years. There's been interchange between whites and blacks on the banjo from at least the early 1700s, maybe even sooner. So, it's hard to generalize on so sweeping and broad a historical phenomenon. Dena Epstein's "Sinful Tunes and Spirituals" is the best book length treatment of black music in the United States before the Civil War. There's much information here on the banjo.
In the late 1800s and early 1900s, there was much more regional variation in performance styles than today, especially in rural areas. Cultural contexts also have had a strong hand in the development of black styles (a very complex issue to deal with here in an email post - but, for as just one example, the ratio of blacks to whites was greater in places like the Delta than in North Carolina, therefore the nature of African American music would be different in these regions). Banjo styles in the Virginia Piedmont were no doubt different than in the Mississippi Delta. Some of this evidence is circumstantial, gathered from the analyses of early 20th century recording-era African American guitar styles. But if you join general historical knowledge to musical knowledge, it's safe to make some assumptions. Folklorist Bruce Bastin has written about this in the introduction to "Red River Blues," his excellent book on the historical development of Piedmont guitar styles. By the way, Charlie Patton's mother was a banjo player!