Host resistance and susceptibility to tomato leaf curl New Delhi virus: molecular mechanisms, genetic resources, and strategies for durable control
Tomato leaf curl New Delhi virus (ToLCNDV) is a highly adaptable begomovirus with an expansive and ever-increasing host range. Since its first report in the Indian subcontinent, the virus has rapidly spread across Asia, the Mediterranean Basin, North Africa, and other areas, largely due to efficient transmission by the whitefly Bemisia tabaci . The virus causes severe economic losses in tomato and cucurbit crops, with reported yield reductions ranging from 80% to 100% depending on crop stage, host genotype, and epidemic severity. ToLCNDV has a bipartite circular single-stranded DNA genome that encodes proteins involved in replication, movement, pathogenicity, and suppression of host defense responses. Rapid host range expansion, emergence of new strains, and breakdown of resistance have been facilitated by its high mutation rate, frequent recombination, genome reassortment, and interactions with associated DNA satellites. This review summarizes the current knowledge on taxonomy, genome organization, epidemiology, transmission biology, host range, and molecular interactions of ToLCNDV with host plants and vectors. Particular attention is given to natural sources of resistance in tomato and cucurbits, the genetic basis of resistance loci, host susceptibility factors, and viral counter-defense strategies. This review also discusses recent advances in genomics, transcriptomics, proteomics, gene editing, and molecular breeding as promising tools for durable disease management. Although progress has been made in resistance gene discovery and host–virus interaction studies, sustainable management remains challenging due to the rapid evolution of viruses and the adaptability of vectors. The future management of ToLCNDV will be based on a combination of resistant cultivars, clean plant material, correct diagnosis, whitefly control, real-time surveillance, and omics-guided breeding strategies. A systems-level understanding of the host–virus–vector relationship will be essential for developing resilient crop production systems under changing climatic and agricultural conditions.