Isolation and Pathogenicity of the Causal Fungus of Black Scorch Disease in Sudanese Date Palm*

Abstract

This study reports the natural occurrence of black scorch
disease in date palm (Phoenix dactylifera L.) in Khartoum and River Nile
States. It also aims at establishing the identity and pathogenicity of the
causal organism. The symptoms consisted of black scorch on fronds,
inflorescence blight, trunk rot and terminal bud rot leading to a
characteristic bend at the region of infection (Medjnoon phenomenon).
Based on the typical visual symptoms, the disease incidence was
estimated at 2% - 4% in Khartoum State and 6% - 10% in the River Nile
State. The fungus, isolated from typical disease lesions, was identified as
Thielaviopsis paradoxa (de Seynes) Von Hohn. depending on its cultural
and morphological characteristics, showing two types of vegetative spores
(microconidia and macroconidia). This was further confirmed by the
pathogenicity test of the isolated fungus which produced the commonly
known pineapple disease symptoms in sugarcane setts. This is the first
confirmation of the occurrence of black scorch disease on date palm in
Sudan, based on the identity and pathogenicity of the causal agent.
Previous reports on the occurrence of this disease in Sudan, however,
relied only on visual symptoms.