Centro de Edafología y Biología Aplicada del Segura (CEBAS), CSIC, Departamento de Biología del Estrés y Patología Vegetal, P.O. Box 164, 30100, Murcia, Spain.
Centro de Investigación e Innovación Agroalimentaria y Agroambiental (CIAGRO), Universidad Miguel Hernández de Elche, Ctra de Beniel km 3,2 03312 Orihuela, Alicante, Spain.
Phytopathology. 2023 Sep;113(9):1761-1772. doi: 10.1094/PHYTO-10-22-0394-V. Epub 2023 Oct 28.
Understanding the emergence and prevalence of viral diseases in crops requires the systematic epidemiological monitoring of viruses, as well as the analysis of how ecological and evolutionary processes combine to shape viral population dynamics. Here, we extensively monitored the occurrence of six aphid-transmitted viruses in melon and zucchini crops in Spain for 10 consecutive cropping seasons between 2011 and 2020. The most prevalent viruses were cucurbit aphid-borne yellows virus (CABYV) and watermelon mosaic virus (WMV), found in 31 and 26% of samples with yellowing and mosaic symptoms. Other viruses, such as zucchini yellow mosaic virus, cucumber mosaic virus, Moroccan watermelon mosaic virus, and papaya ring spot virus, were detected less frequently (<3%) and mostly in mixed infections. Notably, our statistical analysis showed a significant association between CABYV and WMV in melon and zucchini hosts, suggesting that mixed infections might be influencing the evolutionary epidemiology of these viral diseases. We then carried out a comprehensive genetic characterization of the full-length genome sequences from CABYV and WMV isolates by using the Pacific Biosciences single-molecule real-time (PacBio) high-throughput technology to assess the genetic variation and structure of their populations. Our results showed that the CABYV population displayed seven codons under positive selection, and although most isolates clustered in the Mediterranean clade, a subsequent analysis of molecular variance revealed a significant, fine-scale temporal structure, which was in part explained by the level of the variance between isolates from single and mixed infections. In contrast, the WMV population genetic analysis showed that most of the isolates grouped into the Emergent clade, with no genetic differentiation and under purifying selection. These results underlie the epidemiological relevance of mixed infections for CABYV and provide a link between genetic diversity and CABYV dynamics at the whole-genome level.
了解作物中病毒性疾病的出现和流行需要对病毒进行系统的流行病学监测，以及分析生态和进化过程如何结合起来塑造病毒种群动态。在这里，我们在 2011 年至 2020 年的 10 个连续种植季节中，广泛监测了西班牙瓜类和南瓜作物中六种蚜虫传播病毒的发生情况。出现黄化和花叶症状的样本中，最常见的病毒是瓜蚜传黄化病毒（CABYV）和西瓜花叶病毒（WMV），分别占 31%和 26%。其他病毒，如南瓜黄花叶病毒、黄瓜花叶病毒、摩洛哥西瓜花叶病毒和木瓜环斑病毒，检测频率较低（<3%），且大多为混合感染。值得注意的是，我们的统计分析显示，CABYV 和 WMV 在瓜类和南瓜宿主中存在显著关联，表明混合感染可能影响这些病毒性疾病的进化流行病学。然后，我们使用太平洋生物科学公司的单分子实时（PacBio）高通量技术对 CABYV 和 WMV 分离物的全长基因组序列进行了全面的遗传特征分析，以评估其种群的遗传变异和结构。我们的研究结果表明，CABYV 种群有七个密码子受到正选择的影响，尽管大多数分离物聚类在地中海分支中，但随后的分子方差分析显示存在显著的、细尺度的时间结构，这在一定程度上可以用来自单一和混合感染的分离物之间的方差水平来解释。相比之下，WMV 种群遗传分析表明，大多数分离物分为新兴分支，没有遗传分化，受到纯化选择。这些结果表明混合感染对 CABYV 的流行病学相关性，并为整个基因组水平上的遗传多样性和 CABYV 动态之间提供了联系。
