Fusarium Wilt of Sweet Potato Caused by Fusarium oxysporum f.sp. batatas in Egypt

Abstract

Fusarium wilt in sweet potato was first observed in Middle Egyptgovernorates, i.e., Beni Sweif and Minia, between early April toSeptember 2016. Disease symptoms started as a stunted growth,yellowing and wilting of the leaves, browning and discolouration ofthe xylem vessels. Koch’s postulates were fulfilled and all Fusariumoxysporum isolates tested were able to infect sweet potato plantscausing typical wilt symptoms. Prevalence, incidence and severity ofsweet potato wilt (SPW) were varied with districts examined. Fungibelonging to five generae.g., Alternaria, Ceratocystis, Fusarium,Macrophomina and Rhizoctonia were found to be associated withwilted sweet potato plants. Fusarium spp recorded the highestfrequency (80.6%) and Fusarium oxysporum showed 51.5%.frequency. Sweet potato genotypes were varied in their response toinfection by Fusarium oxysporum isolate F1. Genotypes Menoufia 6and Menoufia 2 reacted as resistant, while Local A and Line 26 werehighly susceptible. Fusarium oxysporum f.sp. batatas isolate F1 wasinfective to convolvulaceous plants such as Cairo morning glory andfield bindweed but was not pathogenic to non convolvulaceous plants such as alfalfa, carrot, cotton, potato, sugar beet, sugarcane, turnip andwheat. Chlorophyll degradation was ralated to sweet potato genotypesreaction towards Fusarium oxysporum f.sp. batatas infection. Leastdegradation values were found in resistant genotypes and vice versaexhibited by susceptible genotypes. In contrast, phenols were enhanced when Fusarium oxysporum f.sp. batatas infected theresistant genotypes and decreased in the susceptible genotypes compared with uninfected.