This is a picture of angular leaf spot. All four of these can be distinguished by the lesions they cause on the leaves:

• Angular leaf spot produces water-soaked lesions whose centers turn brown and fall out; the lesions are confined by secondary veins resulting in an angular appearance.
• Scab creates pale yellow-to-white lesions, somewhat angular in shape.
• Septoria leaf spot produces white-to-light brown lesions.
• Downy mildew lesions are angular in shape and produce a dense grey fungi or black fungal spores on the underside of the leaf.