Prediction of Potato Dry Rot Based on the Presence of Fusarium in Soil Adhering to Tubers at Harvest. D. J. Theron, Vegetable and Ornamental Plant Research Institute, Private Bag X293, Pretoria 0001. G. Holz, Department of Plant Pathology, University of Stellenbosch, Stellenbosch 7600, South Africa. Plant Dis. 75:126-130. Accepted for publication 27 June 1990. Copyright 1991 The American Phytopathological Society. DOI: 10.1094/PD-75-0126.

A tuber disk technique for predicting dry rot of potato (Solanum tuberosum) before harvest was developed and compared with other tuber baiting methods. The technique distinguished between pathogenic and nonpathogenic forms of Fusarium. The absolute inoculum potential of Fusarium dry rot pathogens in soil adhering to tubers after lifting could be determined quantitatively. Correlations between assessments of dry rot as it occurs in naturally infected tubers and assessments according to the whole tuber technique (r = 0.92), the naturally infected and the tuber disk technique (r = 0.98), and the whole tuber and tuber disk techniques (r = 0.96) were highly significant (P ≤ 0.001). The tuber disk technique requires only a few tubers, soil samples are easily collected and handled, and results are obtained within 8–10 days. This inexpensive, simple technique could be used commercially to predict the risk of storage rot development.

Keyword(s): inoculum density.