Re: Mary Buckner?? Mary Chew?? or Mary Adkinson ??
I don't think John (II) was married to anyone other than Mary.
I do not know where William Riley Landrum Sr. and his wife are buried but they could be in unmarked graves in at Landrum Cemetery, Hickory Grove, Pearl River County, MS since some of their sons are buried there.Otherwise, check Marion County cemeteries.Personally, my educated guess would be in the Landrum Cemetery in Pearl River Co.