Susceptibility of Lobesia botrana (Lepidoptera: Tortricidae) to chlorantraniliprole in the Emilia Romagna Region of Northeast Italy.

The European grapevine moth, Lobesia botrana (Denis & Schiffermüller) (Lepidoptera: Tortricidae), is regarded as the most important insect pest of wine grapes in Europe. If not properly controlled, it can cause significant direct and indirect yield losses due to secondary infections of grape berries by Botrytis cinerea. For these reasons, it is important to preserve the activity of insecticides used against this pest, as the number of insecticidal mode of actions available to control Lepidoptera species on wine grapes in Europe is limited. Following a report of suboptimal control of L. botrana after field applications of chlorantraniliprole-containing products, an extensive monitoring program was conducted in the Emilia Romagna Region of North East Italy to determine L. botrana susceptibility to chlorantraniliprole. This study consisted of 11 bioassays conducted with chlorantraniliprole on L. botrana populations collected in the Emilia Romagna Region in 2014-2016, 5-7 years after its introduction into the market. Bioassay results were compared to results previously obtained from the chlorantraniliprole pre-comercialization baseline susceptibility survey conducted from 2007 to 2011. The Lethal Concentration values obtained for field populations of L. botrana in this study are comparable to those reported for the pre-comercialization susceptibility baseline. We demonstrate that there is no significant change in L. botrana susceptibility to chlorantraniliprole in the Emilia Romagna Region. Emphasis should be given to implement appropriate insecticide resistance management strategies, including nonchemical agronomic practices and biological control methods, to preserve effective insecticides like chlorantraniliprole for future use in controlling the European grapevine moth.

The biology of Phytophthora infestans at its center of origin.

The central highlands of Mexico are considered to be a center of genetic diversity for both the potato late blight pathogen and for tuber-bearing Solanum spp. Recent work conducted in Mexico and South America sheds new light on the biology and evolution of Phytophthora infestans and other related Phytophthora pathogens. It now appears that Mexican Solanum species, which coevolved with P. infestans and were previously known for providing a source of R-genes, also provide a source of quantitative, rate-reducing resistance that is highly effective, stable, and durable. It is now apparent that Mexico is the center of origin not only of the potato late blight pathogen P. infestans, but also of several related Phytophthora species including P. mirabilis, P. ipomoeae, and possibly P. phaseoli. We close with the hypothesis that these Phytophthora species evolved sympatrically from one ancestral host through adaptive radiation onto their respective four host families.

A Rapid Diagnostic Test to Distinguish Between American and European Populations of Phytophthora ramorum.

ABSTRACT A new devastating disease in the United States, commonly known as Sudden Oak Death, is caused by Phytophthora ramorum. This pathogen, which previously was described attacking species of Rhododendron and Viburnum in Germany and the Netherlands, has established itself in forests on the central coast of California and is killing scores of native oak trees (Lithocarpus densiflora, Quercus agrifolia, Q. kelloggii, and Q. parvula var. shrevei). The phytosanitary authorities in the European Union consider non-European isolates of P. ramorum as a threat to forest trees in Europe. To date, almost all European isolates are mating type A1 while those from California and Oregon are type A2. The occurrence of both mating types in the same region could lead to a population capable of sexual recombination, which could generate a new source of diversity. To prevent contact between these two populations, a rapid, reliable, and discriminating diagnostic test was developed to easily distinguish the two populations. Based on a DNA sequence difference in the mitochondrial Cytochrome c oxidase subunit 1 (Cox1) gene, we developed a single-nucleotide polymorphism (SNP) protocol to distinguish between isolates of P. ramorum originating in Europe and those originating in the United States. A total of 83 isolates of P. ramorum from Europe and 51 isolates from the United States were screened and all isolates could be consistently and correctly allocated to either the European or the U.S. populations using the SNP protocol.

The Population Structure of Phytophthora infestans from the Toluca Valley of Central Mexico Suggests Genetic Differentiation Between Populations from Cultivated Potato and Wild Solanum spp.

ABSTRACT The population structure of Phytophthora infestans in the Toluca Valley of central Mexico was assessed using 170 isolates collected from cultivated potatoes and the native wild Solanum spp., S. demissum and S. xendinense. All isolates were analyzed for mitochondrial DNA (mtDNA) haplotype and amplified fragment length polymorphism (AFLP) multi-locus fingerprint genotype. Isolate samples were monomorphic for mtDNA haplotype because all isolates tested were of the Ia haplotype. A total of 158 multilocus AFLP genotypes were identified among the 170 P. infestans isolates included in this study. P. infestans populations sampled in the Toluca Valley in 1997 were highly variable and almost every single isolate represented a unique genotype based on the analysis of 165 AFLP marker loci. Populations of P. infestans collected from the commercial potato-growing region in the valley, the subsistence potato production area along the slopes of the Nevado de Toluca, and the native Solanum spp. on the forested slopes of the volcano showed a high degree of genetic diversity. The number of polymorphic loci varied from 20.0 to 62.4% for isolates collected from the field station and wild Solanum spp. On average, 81.8% (135) of the AFLP loci were polymorphic. Hetero-zygosity varied between 7.7 and 19.4%. Significant differentiation was found at the population level between strains originating from cultivated potatoes and wild Solanum spp. (P = 0.001 to 0.022). Private alleles were observed in individual isolates collected from all three populations, with numbers of unique dominant alleles varying from 9 to 16 for isolates collected from commercial potato crops and native Solanum spp., respectively. Four AFLP markers were exclusively found present in isolates collected from S. demissum. Indirect estimation of gene flow between populations indicated restricted gene flow between both P. infestans populations from cultivated potatoes and wild Solanum hosts. There was no evidence found for the presence of substructuring at the subpopulation (field) level. We hypothesize that population differentiation and genetic isolation of P. infestans in the Toluca Valley is driven by host-specific factors (i.e., R-genes) widely distributed in wild Solanum spp. and random genetic drift.