Molecular and biological characterization of Peruvian isolates of zucchini yellow mosaic virus reveals differential severity and partial resistance breakdown in zucchini cultivars

Abstract

Abstract Zucchini yellow mosaic virus (ZYMV) is one of the most important potyviruses affecting cucurbit crops worldwide and has recently been reported in Peru. However, information regarding the biological variability and host response of Peruvian isolates remains limited. This study aimed to characterize two Peruvian ZYMV isolates obtained from conventional and organic zucchini production systems, as well as to evaluate their aggressiveness in four commercial zucchini cultivars under greenhouse and field conditions. Symptom severity was assessed using a proposed diagrammatic scale, while genomic characterization was performed through high-throughput sequencing, followed by phylogenetic analysis based on the complete sequences of the polyprotein-coding region. Both isolates, ZYMV_Lim and ZYMV_Chos, induced typical ZYMV symptoms; however, ZYMV_Chos caused more severe symptoms, particularly in the cultivar ‘Hurakan F1’, indicating greater aggressiveness. Comparative genomic analysis revealed amino acid differences mainly in the P1 and HC-Pro regions, which may contribute to differences in pathogenicity and host interaction in potyviruses. Phylogenetic analysis grouped the Peruvian isolates with sequences from the United Kingdom, the United States, and Australia, suggesting independent introduction events. Under field conditions, the cultivar ‘Rocío F1’ exhibited lower symptom incidence, reduced disease progression, and superior agronomic performance. The biological and molecular differences identified among the Peruvian isolates were associated with contrasting responses in the evaluated cultivars. The use of tolerant cultivars such as ‘Rocío F1’ may represent a practical alternative for reducing ZYMV damage under field conditions.