Evaluation of the Efficacy of Different Levels of Inorganic Salts and Varieties for the Management of Late blight of Potato under Laboratory and Field Conditions

Abstract

Resistance to late blight disease in potato varieties is broken down due to the emergence of virulent races of Phytophthora infestans. There is no variety grown without fungicide spray. Chemicals pose a serious threat to the environment and human health. Laboratory study was conducted at Adet plant pathology lab in 2018 and field studies were conducted at Adet and Debre Tabor experimental sites in 2018 and 2019. The objective of the study was to determine the effect of inorganic salts and host plant resistance against late blight of potato. Eight inorganic salts were evaluated in the laboratory in detached leaf assay technique and effective inorganic salts were selected and integrated with three potato varieties in factorial arrangement in the field. Results of the laboratory study indicated that inorganic salts posed significant (P<0.01) inhibitory effect on infection and lesion growth. Treating leaves with Ridomil fungicide, Potassium phosphite and Potassium phosphate at the rate of 20 g l^-1 reduced leaf lesion area by 99.4, 95.6 and 95.5%, respectively. The effect of inorganic salt by variety interaction on the area under disease progress curve (AUDPC) was significant (P<0.01). The fungicide sprayed plots significantly reduced the AUDPC values on the varieties. But, such reductions were not significant compared to potassium phosphite sprayed plots of Belete and Gudene varieties over locations. The relative yield loss of the untreated (control) plots of the susceptible variety (Jalene) were 43.21 and 59.74%, whereas K₂HPO₃ treated plots were 18.63 and 15.64% in 2018 and 2019 respectively. Therefore, even treating susceptible varieties with inorganic salts could result in minimizing the damage of late blight disease on potatoes. In conclusion, integration of potassium phosphite with resistant (Belete) and moderately resistant (Gudene) varieties is identified as the best alternative option to manage late blight of potato.