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

Document Type : Original Article

Authors

1 Plant Pathol. Dept., Fac. Agric., Minia Univ., Egypt

2 Plant Pathology Research Institute, ARC, Giza, Egypt

3 Horticultural Research Institute, ARC, Giza, Egypt

Abstract

Fusarium wilt in sweet potato was first observed in Middle Egypt
governorates, i.e., Beni Sweif and Minia, between early April to
September 2016. Disease symptoms started as a stunted growth,
yellowing and wilting of the leaves, browning and discolouration of
the xylem vessels. Koch’s postulates were fulfilled and all Fusarium
oxysporum isolates tested were able to infect sweet potato plants
causing typical wilt symptoms. Prevalence, incidence and severity of
sweet potato wilt (SPW) were varied with districts examined. Fungi
belonging to five generae.g., Alternaria, Ceratocystis, Fusarium,
Macrophomina and Rhizoctonia were found to be associated with
wilted sweet potato plants. Fusarium spp recorded the highest
frequency (80.6%) and Fusarium oxysporum showed 51.5%.
frequency. Sweet potato genotypes were varied in their response to
infection by Fusarium oxysporum isolate F1. Genotypes Menoufia 6
and Menoufia 2 reacted as resistant, while Local A and Line 26 were
highly susceptible. Fusarium oxysporum f.sp. batatas isolate F1 was
infective to convolvulaceous plants such as Cairo morning glory and
field bindweed but was not pathogenic to non convolvulaceous plants
such as alfalfa, carrot, cotton, potato, sugar beet, sugarcane, turnip and
wheat. Chlorophyll degradation was ralated to sweet potato genotypes
reaction towards Fusarium oxysporum f.sp. batatas infection. Least
degradation values were found in resistant genotypes and vice versa
exhibited by susceptible genotypes. In contrast, phenols were
enhanced when Fusarium oxysporum f.sp. batatas infected the
resistant genotypes and decreased in the susceptible genotypes
compared with uninfected.

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