Assessment of the genetic diversity of tomato yellow leaf curl virus

High-Throughput Sequencing Reveals Differential Begomovirus Species Diversity in Non-Cultivated Plants in Northern-Pacific Mexico

Plant DNA viruses of the genus Begomovirus have been documented as the most genetically diverse in the family Geminiviridae and present a serious threat for global horticultural production, especially considering climate change. It is important to characterize naturally existing begomoviruses, since viral genetic diversity in non-cultivated plants could lead to future disease epidemics in crops. In this study, high-throughput sequencing (HTS) was employed to determine viral diversity of samples collected in a survey performed during 2012–2016 in seven states of Northern-Pacific Mexico, areas of diverse climatic conditions where different vegetable crops are subject to intensive farming. In total, 132 plant species, belonging to 34 families, were identified and sampled in the natural ecosystems surrounding cultivated areas (agro-ecological interface). HTS analysis and subsequent de novo assembly revealed a number of geminivirus-related DNA signatures with 80 to 100% DNA similarity with begomoviral sequences present in the genome databank. The analysis revealed DNA signatures corresponding to 52 crop-infecting and 35 non-cultivated-infecting geminiviruses that, interestingly, were present in different plant species. Such an analysis deepens our knowledge of geminiviral diversity and could help detecting emerging viruses affecting crops in different agro-climatic regions.

Elevated O₃ and TYLCV Infection Reduce the Suitability of Tomato as a Host for the Whitefly Bemisia tabaci

The effects of elevated atmospheric ozone (O₃) levels on herbivorous insects have been well studied, but little is known about the combined effects of elevated O₃ and virus infection on herbivorous insect performance. Using open-top chambers in the field, we determined the effects of elevated O₃ and Tomato yellow leaf curl virus (TYLCV) infection on wild-type (Wt) tomato and 35S tomato (jasmonic acid (JA) defense-enhanced genotype) in association with whitefly, Bemisia tabaci Gennadius biotype B. Elevated O₃ and TYLCV infection, alone and in combination, significantly reduced the contents of soluble sugars and free amino acids, increased the contents of total phenolics and condensed tannins, and increased salicylic acid (SA) content and the expression of SA-related genes in leaves. The JA signaling pathway was upregulated by elevated O₃, but downregulated by TYLCV infection and O₃ + TYLCV infection. Regardless of plant genotype, elevated O₃, TYLCV infection, or O₃ + TYLCV infection significantly decreased B. tabaci fecundity and abundance. These results suggest that elevated O₃ and TYLCV infection, alone and in combination, reduce the nutrients available for B. tabaci, increase SA content and SA-related gene expression, and increase secondary metabolites, resulting in decreases in fecundity and abundance of B. tabaci in both tomato genotypes.