Screening for late blight susceptibility in potato tubers by digital analysis of cut tuber surfaces

A method for quantification of late blight (Phytophthora infestans) in pota to tuber tissue using a digital scanner and image analysis software is pres ented. The average reflective intensity of light reflected from the cut sur face of sample tubers measures the darkened, diseased potato tuber tissue a mid lighter, late blight-free tissue. In the absence of disease, potato var iety, tuber shape, and tuber size do not influence the scan results. While digital quantification of late blight in tubers under controlled inoculatio n conditions is consistent, the digital assessments of late blight did not correspond exactly with those from a conventional subjective visual method. Used together, the methods can provide complementary information regarding varietal susceptibility to P. infestans development on the tuber surface a nd internal tuber tissue. The method of image analysis presented may be use d to determine susceptibility of potato tubers to late blight in varietal d evelopment programs, storage research programs, or other tuber research pro grams.