Genomic Component Interactions Shape Host-Specific Systemic Infection in Tomato Leaf Curl New Delhi Virus

Area of Science:

• Plant virology
• Molecular plant pathology
• Begomovirus research

Background:

• Tomato leaf curl New Delhi virus (ToLCNDV) exhibits geographic variation in host adaptation.
• Asian and Mediterranean ToLCNDV isolates differ in their ability to infect solanaceous crops versus cucurbits.

Purpose of the Study:

• To investigate the molecular basis for host adaptation divergence in ToLCNDV isolates.
• To identify the viral components responsible for differential infectivity in tomato and other hosts.

Main Methods:

• Reciprocal pseudo-recombinant analysis of Indian (ToLCNDV-IN) and Spanish (ToLCNDV-ES) isolates.
• Infection assays in *Solanum lycopersicum* (tomato) and *Nicotiana benthamiana*.
• Analysis of coat protein (CP) function in systemic movement.

Main Results:

• DNA-A replication occurred in tomato for both isolates; DNA-B determined tomato infectivity, with DNA-B-IN supporting systemic infection more efficiently.
• DNA-B was essential for systemic infection in tomato but enhanced, not essential, for movement in *N. benthamiana*.
• A CP-mutated ToLCNDV-ES isolate failed systemic infection, indicating CP's essential role in movement.

Conclusions:

• DNA-B is a major determinant of ToLCNDV infectivity in tomato.
• Coat protein is crucial for the systemic movement of Mediterranean ToLCNDV isolates.