In a recent survey of post-harvest rot pathogens in European pear in Southern Oregon, Alternaria spp. were frequently isolated from orchard samples of pear flowers and fruits. Morphological differences were observed within the isolated cultures. A preliminary NCBI BLAST search analysis using sequences of the ATPase locus across 94 isolates of Alternaria spp. obtained from pear fruit rots revealed three major Alternaria sections: sect. Alternata, sect. Infectoriae, and sect. Ulocladioides. Thirteen isolates were selected based on their genetic and morphological diversity across three Alternaria sections and were subjected to multilocus phylogenetic analysis using sequences from plasma membrane ATPase, calmodulin, and Alt a1 loci. Within sect. Alternata, four Alternaria arborescens isolates and one A. destruens isolate were identified; within sections Infectoriae and Ulocladioides, one A. rosae isolate and two A. botrytis isolates were identified, respectively. The remaining five isolates could not be identified based on the available sequences for the three loci used in this study. In addition to the phylogenetic analysis, pathogenicity assays revealed differential responses to these isolates on four pear cultivars: Anjou, Bartlett, Comice, and Bosc. Inoculation of isolates within Alternaria sect. Alternata resulted in fruit lesions across all cultivars, with Bosc pear being significantly susceptible (P < 0.0001). Isolates within Alternaria sect. Ulocladioides caused rots on Anjou and Bosc pears, while isolates within Alternaria sect. Infectoriae developed rots on Bosc pear only. This study suggests that there is differential susceptibility of pear cultivars to Alternaria rots, and the severity of post-harvest rot depends on the type of Alternaria spp. and cultivar predominant in a region.

Background and goals Grapevine red blotch disease (GRBD) is caused by grapevine red blotch virus (GRBV). GRBD diagnosis is often challenging because of the nature of symptoms in grapevines and complexity of testing methods. In 2020 and 2021, we compared the accuracy of four GRBV detection methods using samples collected from a commercial vineyard in southern Oregon. Methods and key findings Tissue samples were collected at fruit set, veraison, harvest, and dormancy from basal, middle, and apical shoot nodes of 20 GRBV-positive and negative vines. GRBD symptoms on grapevines were recorded at the time of collection, and leaf samples were tested for GRBV using loop-mediated isothermal amplification (LAMP), endpoint PCR, and quantitative PCR (qPCR). The detectability of GRBV-positive vines by the assays differed significantly among node positions, depending on phenology. At fruit set and veraison, the sensitivity of qPCR and endpoint PCR assays was 98%, whereas the sensitivity of LAMP was 49% and 78%, respectively, from basal leaf samples. At harvest and dormancy, the sensitivity of all assays was 100% in basal and middle samples, and no significant differences were detectable between LAMP, endpoint PCR, and qPCR. None of the GRBV-positive grapevine samples expressed symptoms at fruit set, and 31% of the basal canopy samples expressed symptoms at veraison. At harvest, 90% of these vines expressed symptoms, which was not significantly different than other methods. Similarly, at fruit set, the specificity of LAMP was less than 75%, whereas at veraison and harvest, it increased to 100% for all DNA-based detection methods. Conclusions and significance The results of this study show that PCR-based assays are the most accurate option if early diagnosis is needed; less expensive methods such as LAMP and basal canopy symptoms are reliable at later phenological stages. These findings contribute to the better understanding of GRBV detection and benefit other researchers, winegrape, and nursery industries.

Spring frost is a perennial and widespread problem across many cool climatic and high-elevation winegrowing regions of the world. Vitis vinifera L. cv. Pinot noir is an early budding cultivar; thus, it is particularly susceptible to late-spring frost damage. In late April 2022, an advective frost event occurred throughout Western Oregon winegrowing regions and subsequently damaged a substantial number of commercial vineyards. Growers often are unsure of how to manage grapevines after a frost event. Limited research has shown little-to-no effect of pruning vs. non-pruning strategies on vine yield and productivity. In addition, pruning a frost-affected vineyard incurs additional labor costs that may offset the cost–benefit balance for the grower. Therefore, in this experiment, the effect of two different post-frost pruning treatments (cane pruning and spur pruning) on vine yield, berry composition, and vine vegetative growth were tested. No effect of post-frost pruning treatments on vine yield, berry composition, and vine vegetative characteristics was observed. Cluster numbers, cluster weights, and berries per cluster only differed between cane- vs. spur-pruned vines. Therefore, leaving frost-affected vines alone and a scaled-back vineyard management practice could be practical for economic reasons.

Background and goals Grapevine red blotch virus (GRBV) is a major pathogen of Vitis vinifera L. that causes the eponymous grapevine red blotch disease (GRBD). This disease is characterized by reduced leaf carbon assimilation and delayed berry ripening, resulting in diminished fruit quality. Recent work suggests that the virus alters leaf carbon metabolism prior to emergence of visible symptoms. However, the physiological manifestation of this altered metabolism is currently unknown. Therefore, an experiment was conducted to unravel the progression of GRBD symptoms in field-grown Pinot noir grapevines. Methods and key findings Diurnal and seasonal measurements were conducted to quantify changes in leaf carbon balance and chronologize symptom progression in leaves and fruit. Leaf-level physiology was measured as a function of water relations, photosynthesis, and nonstructural carbohydrates in a commercial vineyard containing both healthy and infected vines. Additionally, fruit sugar and anthocyanin accumulation were monitored during ripening. Virus infection reduced carbon assimilation pre- and postveraison, but the effect was more pronounced postveraison and during the afternoon. Similarly, virus infection significantly increased leaf starch concentration pre- and postveraison. Starch granules accumulated in the chloroplasts and caused apparent damage to their structural and functional integrity. The virus had no sustained impact on chlorophyll fluorescence, suggesting that changes in fluorescence were a transient response to reduced carbon assimilation and export. Conclusions and significance This study provides evidence that GRBV infection causes starch accumulation in infected leaves, which may have downstream effects on leaf carbon metabolism and ripening prior to the appearance of visible symptoms.

Background and goals Pinot noir is one of the most popular winegrape varieties worldwide, but because of its origins in more cool-climate wine production regions, there is little information regarding its responses to regulated deficit irrigation practices in warm and semiarid climates. Thus, the objective of this study was to observe the responses of Pinot noir production and fruit quality characteristics to preveraison (anthesis to veraison) and postveraison (veraison to harvest) deficit irrigation over two growing seasons. Methods and key findings Treatments consisted of pre- and postveraison irrigation levels at fractions (25, 50, 75, and 100%) of estimated crop evapotranspiration (ET_c). Vine water status (stem water potential [Ψ_stem]) was strongly correlated with applied irrigation during both periods, but particularly during preveraison. Accordingly, berry weight was significantly and linearly reduced with preveraison deficit irrigation, but there was no significant berry weight response to postveraison deficit irrigation. All skin phenolic compound classes—anthocyanins, tannins, and iron-reactive phenolics—showed an inverse linear relationship with preveraison deficit irrigation rate, while these responses to postveraison deficit irrigation were quadratic, both on a concentration and a content basis. With preveraison deficit irrigation, a negative linear relationship was observed between berry phenolics such that the greatest preveraison deficit had the highest total phenolics. In contrast, berry phenolic composition improved with moderate postveraison deficit irrigation and no negative yield effects were observed. The preveraison irrigation rate of 25% of ET_c and postveraison rates between 50 to 75% ET_c maximized berry phenolics without a significant reduction in vine yield. Conclusions and significance In summary, the results indicate that severe deficit irrigation preveraison, and mild to moderate deficit irrigation postveraison, improve berry phenolics in warm-climate Pinot noir.