A relatively new variety (1998), specific to quince (Cydonia oblonga), identified from research carried out in India. There are no records on NBN Atlas for Britain. This was found on our young quince tree in our polycrub. The nominate variety is common, found on numerous trees and shrubs.

References: 
Braun, U. & Cook, T.A. (2012). Taxanomic Manual of the Erysiphales (Powdery Mildews).