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PubMed2026

Cucurbit Leaf Crumple Virus: An Important Pathogen of Cucurbit and Snap Bean Crops.

TAXONOMY: Cucurbit leaf crumple virus (CuLCrV); Begomovirus cucurbitae; Geminiviridae; Geplafuvirales. GEOGRAPHICAL DISTRIBUTION: The presence of CuLCrV is exclusively limited to North America, mainly Mexico and the United States. PHYSICAL PROPERTIES: CuLCrV is a bipartite begomovirus comprising two circular single-stranded DNA molecules (DNA-A and DNA-B), encapsidated within geminate icosahedral particles. GENOME AND ORGANIZATION: CuLCrV possesses a bipartite genome of DNA-A (2632 nucleotides) and DNA-B (2600 nucleotides). DNA-A contains five open reading frames (ORFs): AV1 (coat protein), AC1 (replication-associated protein), AC2 (transcriptional activator protein), AC3 (replication enhancer protein) and AC4. DNA-B contains two ORFs: BV1 (nuclear shuttle protein) and BC1 (movement protein). TRANSMISSION: CuLCrV is transmitted by the sweetpotato whitefly, Bemisia tabaci, in a persistent, circulative and non-propagative manner. HOSTS: CuLCrV primarily infects crop members of the Cucurbitaceae and snap bean (Phaseolus vulgaris, Fabaceae). Multiple weed species belonging to Brassicaceae, Convolvulaceae, Cucurbitaceae and Verbenaceae act as persistent virus reservoir hosts. SYMPTOMS: Symptom expression varies with host and infection timing. In cucurbits, infection induces leaf crumpling, thickening and downward curling of leaves, with green streaks and distortion of fruits. In snap bean, symptoms include leaf distortion, chlorosis and malformed pods. CONTROL: No commercial cultivars with resistance to CuLCrV are available for cucurbit crops, although some resistance has been reported in snap bean cultivars. Therefore, management relies primarily on integrated disease management.

Plant Diseases↗

PubMed2026

A dominant mutation in tomato DNA POLYMERASE DELTA 1 causes geminivirus DNA replication catastrophe.

Geminiviruses pose a severe threat to grain and vegetable crops worldwide, often resulting in significant economic losses. In cultivated tomato (Solanum lycopersicum), Ty resistance alleles have been introduced from wild tomato relatives, providing partial to strong resistance to geminivirus infections. The Ty-6 resistance locus from Solanum chilense was previously mapped to chromosome 10. It was recently shown to contain a mutant allele of the DNA POLYMERASE DELTA 1 (POLD1) gene that provides resistance to Tomato yellow leaf curl virus (TYLCV) infections. However, the resistance mechanism remained unknown. Here, we report another POLD1 allele at the Ty-6 locus of S. chilense with an E622D mutation in the catalytic site of the POLD1 protein. POLD1E622D is maintained as a heterozygous dominant allele in S. chilense and the AVTO2225 breeding line. It provides full resistance to the severe TYLCV Thailand (TYLCTHV) strain. The E622D amino acid change does not alter the predicted structure of POLD1. Replication of the TYLCTHV genome in plants carrying the POLD1E622D allele is severely compromised by a high frequency of mutations that accumulate in viral DNA, which results in nonfunctional proteins that are essential for continuous viral replication. Ectopically expressing the POLD1E622D allele cDNA alone causes mutations in TYLCTHV genes in inoculated leaves. S. chilense and AVTO2225 plants carrying the POLD1E622D allele mount a hypersensitive response after TYLCTHV infection, indicating that the defective virus genome cannot suppress the plant defense. The dominant POLD1E622D allele is therefore an effective resistance gene that geminiviruses cannot overcome.

DNA Replication↗