The effect of biological soil disinfestation on dry rot disease in industrial potatoes caused by Fusarium oxysporum

Objective
Biological soil disinfestation methods have been employed as an alternative to methyl bromide, as they are effective in eliminating soil-borne pathogens, environmentally safe, and cost-effective. The aim of this study was to evaluate the efficiency of the biological disinfestation method using three local organic materials in controlling the pathogenic fungus Fusarium oxysporum on industrial potato crops.
Materials and methods
Industrial potato tubers were collected from various potato-growing regions in Baghdad Province. Three tubers were used for each fungal isolate. The inoculated tubers were stored in an incubator at 15°C with 70–85% humidity for 30 days. This study identified 30 isolates of Fusarium spp. from infected potato tubers and roots, showing significant variation in growth rates, colony colors, and mycelia density. The severity of infection was calculated based on a scale related to root weight, and various growth parameters were measured, including the number of branches, branch length, number of tubers, tuber weight, and the fresh and dry weight of the root system. The experiment was conducted using a randomized complete block design (RCBD).
Results
Pathogenicity tests on potato buds revealed that isolates F1, F5, F8, F10, F15, F20, F21, F28, and F30 caused the highest infection severity, ranging from 75% to 100%. Similarly, the tests on potato tubers confirmed that all isolates could induce dry rot, with damaged tissue areas ranging from 39.16 to 59.64 mm², significantly differing from the control treatment. In Biological disinfestation tests, wheat bran at concentrations of 100, 200, and 300 g/m² significantly reduced infection severity, ranging from 5% to 26%, compared to the 100% infection in the pathogenic fungus control. Sawdust also showed significant reductions, with infection severity between 46% and 60%, while corn husks reduced infection severity to a range between 60% and 80%. Wheat bran demonstrated superior performance in tuber weight, producing tuber weights of 282 g, 362.10 g, and 469.53 g per plant, significantly higher than the control (150 g per plant). In additional biological disinfestation tests, wheat bran reduced infection severity by 25% to 50%, sawdust by 50% to 75%, and corn husks by 66% to 91%, compared to the control with 100% infection.
Conclusions
Tuber weights for these treatments were also significantly higher than the control, with wheat bran showing the best results. Overall, biological soil disinfestation treatments, especially wheat bran, are promising methods for controlling Fusarium infections and improving potato tuber yield.