A Fresh Look at Grape Powdery Mildew (Erysiphe necator) A and B Genotypes Revealed Frequent Mixed Infections and Only B Genotypes in Flag Shoot Samples
PLANTS-BASEL
Authors: Csikos, Anett; Nemeth, Mark Z.; Frenkel, Omer; Kiss, Levente; Vaczy, Kalman Zoltan
Abstract
Erysiphe necator populations, causing powdery mildew of grapes, have a complex genetic structure. Two genotypes, A and B, were identified in most vineyards across the world on the basis of fixed single nucleotide polymorphisms (SNPs) in several DNA regions. It was hypothesized that A populations overwinter as mycelia in grapevine buds, giving rise to so-called flag shoots in spring, and are more sensitive to fungicides than B populations, which overwinter as ascospores and become widespread later in the season. Other studies concluded that the biological significance of these genotypes is unclear. In the spring of 2015, there was a unique opportunity to collect E. necator samples from flag shoots in Hungary. The same grapevines were sampled in summer and autumn as well. A total of 182 samples were genotyped on the basis of beta-tubulin (TUB2), nuclear ribosomal DNA (nrDNA) intergenic spacer (IGS), and internal transcribed spacer (ITS) sequences. Genotypes of 56 samples collected in 2009-2011 were used for comparison. Genotype A was not detected at all in spring, and was present in only 19 samples in total, mixed with genotype B, and sometimes with another frequently found genotype, designated as B2. These results did not support the hypothesis about temporal isolation of the two genotypes and indicated that these are randomly distributed in vineyards.
Characterization of overwintering sites of Haemaphysalis longicornis (Acari: Ixodidae) and tick infection rate with severe fever with thrombocytopenia syndrome virus from eight provinces in South Korea
TICKS AND TICK-BORNE DISEASES
Authors: Kim, Joo-Young; Jung, Minhyung; Kho, Jung-Wook; Song, Hyunsung; Moon, KyungHwan; Kim, Young Ho; Lee, Doo-Hyung
Abstract
Haemaphysalis longicornis (Acari: Ixodidae) is an important vector of pathogens causing tick-borne diseases such as severe fever with thrombocytopenia syndrome (SFTS) in eastern Asia. Although an understanding of the overwintering ecology of ticks is fundamental to management of this vector, its winter biology remains unclear. Therefore, we conducted a field survey from eight provinces in South Korea to characterize overwintering sites of H. longicornis and investigate their SFTS virus infection rates. First, we conducted flagging which consists of horizontal sweeping of a 1 m(2) cloth back-and-forth to collect ticks that may exhibit questing behaviors in four different landscapes: grassland, shrub, coniferous forest, and deciduous forest. From 640 sweeps of flagging (where each sweep covered 3.8 m(2)), we collected five unfed ixodid ticks. However, H. longicornis was not found. After the flagging, to locate overwintering ticks, we inspected a total of 679 samples consisting of three different structures: ground (leaf litter, soil surface, and topsoil layer), rocks, and dead trees. From the samples inspected, 85 unfed overwintering ixodid ticks were found. Haemaphysalis longicornis was the dominant species (88 %), and mostly nymphs were collected (94 %). This species was collected from ground samples, especially from the topsoil layer. Most H. longicornis were found in herbaceous landscapes such as grassland (46 %) and shrub (52 %). SFTS virus was found in 3 out of 38 pools of unfed nymphs (minimal infection rate: 4 %). Our results can serve as baseline information for the development of vector management programs.