Abstract

Tomato yellow leaf curl virus (TYLCV) poses a significant threat to tomato production in Egypt. This study investigated the genetic diversity and biological characteristics of TYLCV isolates circulating in Egyptian tomato fields. A combination of visual observations, serological, and molecular techniques were employed to detect and quantify the virus in infected plants. Positive samples were categorized based on symptom severity to explore the variable effects of different TYLCV isolates. Disease Severity Index, incidence, and virus concentration were analyzed to understand the behavior and impact of these isolates. DAS-ELISA, PCR, and multiplex-PCR (mPCR) targeting the partial coat protein (pCP) gene were used for virus detection. Phylogenetic analysis revealed that the isolates were highly related (99%) to the TYLCV-IL group and moderately related (97%) to the TYLCV-mild group. Beta-satellite presence and its association with symptom severity were also investigated. The study highlights the genetic diversity and biological variability of TYLCV isolates in Egypt, leading to variable symptom expression and disease severity. Understanding these characteristics is crucial for developing effective management strategies and breeding for resistance against TYLCV in tomato crops.