Temporal Epidemics of Potato Late Blight (Phytophthora Infestans) in Major Potato Growing Areas of Ethiopia

Abstract

Potato late blight, caused by the oomycete Phytophthora infestans, is a catastrophic disease worldwide and causes an estimated potato yield loss of about 30–100% in Ethiopia. The research was conducted at Haramaya, Negele Arsi, and Holeta during the 2022 and 2023 cropping seasons to analyze the dynamics of potato late blight epidemics under natural infection. Four potato varieties (Gudene, Jalene, Belete, and Bubu) were arranged in a randomized complete block design with three replications. Disease progress was assessed using percentage of severity index (PSI), area under disease progress curve (AUDPC), relative AUDPC (rAUDPC) and disease progress rate. Significant differences (P < 0.001) were observed among varieties. The variety Gudene and Bubu consistently exhibited lower PSI values at Haramaya, while the variety Gudene recorded the lowest PSI (22.5%), AUDPC (549.07% - days), and disease progress rate ((0.097 units day^˗1) at Holeta. In contrast, Jalene showed the highest rAUDPC values, reaching 40.11% in 2022 and 37.67% in 2023 at Haramaya, and constantly suffered maximum disease severity up to 65.2%. At Negele Arsi, variety Belete and Gudene displayed lower PSI, disease progress rates, and AUDPC values. Across all locations the variety Gudene exhibited the lowest potato late blight severity, whereas variety Jalene was the most susceptible. Based on late blight severity assessment and tuber yield measured, it is recommended that farmers in Haramaya should cultivate Gudene and Bubu, while those in Negele Arsi and Holeta consider Belete and Gudene varieties to reduce potato late blight epidemics and increase potato yield.