Impacts of Grapevine Leafroll Disease on Fruit Yield and Grape and Wine Chemistry in a Wine Grape (Vitis vinifera L.) Cultivar

Grapevine leafroll disease (GLD) is an economically important virus disease affecting wine grapes (Vitis vinifera L.), but little is known about its effect on wine chemistry and sensory composition of wines. In this study, impacts of GLD on fruit yield, berry quality and wine chemistry and sensory features were investigated in a red wine grape cultivar planted in a commercial vineyard. Own-rooted Merlot vines showing GLD symptoms and tested positive for Grapevine leafroll-associated virus 3 and adjacent non-symptomatic vines that tested negative for the virus were compared during three consecutive seasons. Number and total weight of clusters per vine were significantly less in symptomatic relative to non-symptomatic vines. In contrast to previous studies, a time-course analysis of juice from grapes harvested at different stages of berry development from symptomatic and non-symptomatic vines indicated more prominent negative impacts of GLD on total soluble solids (TSS) and berry skin anthocyanins than in juice pH and titratable acidity. Differences in TSS between grapes of symptomatic and non-symptomatic vines were more pronounced after the onset of véraison, with significantly lower concentrations of TSS in grapes from symptomatic vines throughout berry ripening until harvest. Wines made from grapes of GLD-affected vines had significantly lower alcohol, polymeric pigments, and anthocyanins compared to corresponding wines from grapes of non-symptomatic vines. Sensory descriptive analysis of 2010 wines indicated significant differences in color, aroma and astringency between wines made from grapes harvested from GLD-affected and unaffected vines. The impacts of GLD on yield and fruit and wine quality traits were variable between the seasons, with greater impacts observed during a cooler season, suggesting the influence of host plant × environment interactions on overall impacts of the disease

Wheat Curl Mite: A New Source of the Eriophyoid Mite in Wheat Fields Identified

Wheat curl mites (WCMs; Aceria tosichella) are an important global pest of cultivated wheat. Their feeding activities on epidermal cells of wheat leaves result in characteristic leaf curl symptoms that prevent the unfurling of affected leaves and impair the proper emergence of heads from the boot stage. The most significant economic impact of WCM infestation, however, is their ability to vector and transmit four important viruses of wheat, specifically, wheat streak mosaic virus, Triticum mosaic virus, High Plains wheat mosaic emaravirus, and brome streak mosaic virus. Being wingless, WCMs are almost completely dependent on air currents for their dispersal. In addition, because of their obligate lifestyle, wheat field infestations are thought to originate from sources such as volunteer wheat. Corn and other cultivated and noncultivated Poaceae hosts are also known to act as green bridges between successive wheat crops. Consequently, management practices mostly target these off-season host plants but also the use of resistant varieties and other cultural control methods. Here we report the discovery of seed-borne WCM eggs, a previously unknown method of their dispersal, as a possible source of new infestations in wheat fields. This discovery expands our understanding of the biology of WCMs, with potential implications for the development of more holistic and effective management strategies for this economic pest and virus vector. [Graphic: see text] Copyright © 2022 The Author(s). This is an open access article distributed under the CC BY 4.0 International license

Report on the first detection of Asian citrus psyllid Diaphorina citri Kuwayama (Hemiptera: Liviidae) in the Republic of Benin, West Africa

Abstract The Asian citrus psyllid (ACP), Diaphorina citri, was detected for the first time in the Republic of Benin, West Africa. The ACP is a known vector of Candidatus Liberibacter asiaticus (CLas), the putative causal agent of the devastating Huanglongbing (HLB; citrus greening disease). During visual surveys, ACP was only observed on residential citrus trees in southern Benin, but not in residential areas or commercial groves in the central and northern parts of the country. Its identity was confirmed morphologically and molecularly via DNA barcoding with published primers. Analysis of the obtained sequences showed that the ACP recorded in Benin clustered with the ones previously reported from Nigeria, suggesting a common origin of both populations. The ACP samples from Benin also carried Ca. Carsonella ruddii and Ca. Profftella armatura, two commonly found ACP endosymbionts. However, all the sampled ACP individuals tested negative for Ca. Liberibacter africanus, Ca. Liberibacter americanus, and CLas by quantitative polymerase chain reaction. This is the second report of the ACP in West Africa after Nigeria, the eastern bordering country of the Republic of Benin. Benin has an expanding commercial citrus industry, especially in the southern part of the country. Although the ACP samples tested negative for the HLB associated bacteria, the detection of ACP in the country requires swift actions including area-wide surveys to determine the extent of spread of this pest and the implementation of eradication or control efforts to prevent its establishment and spread of HLB in the country

Vascular Access

Molecular characterization and impacts of a strain of Grapevine leafroll-associated virus 2 causing asymptomatic infection in a wine grape cultiva

Near-Complete Genome Sequence of Grapevine Fabavirus, a Novel Putative Member of the Genus Fabavirus.

A novel virus-like sequence from grapevine was identified by Illumina sequencing. The genomic organization was most similar to that of members of the genus Fabavirus Polyproteins RNA-1 and RNA-2 of the virus tentatively named grapevine fabavirus (GFabV) shared 34 to 23% sequence identities with Broad bean wilt virus 2 (BBWV2), respectively. GFabV was successfully graft transmitted to Vitis vinifera cv. Cabernet Franc

Mitigation of Huanglongbing: Implications of a Biologically Enhanced Nutritional Program on Yield, Pathogen Localization, and Host Gene Expression Profiles

Huanglongbing (HLB, citrus greening disease), the most destructive disease affecting citrus production, is primarily linked to the gram-negative, insect-vectored, phloem-inhabiting α-proteobacterium 'Candidatus Liberibacter asiaticus' (CLas). With no effective treatment available, management strategies have largely focused on the use of insecticides in addition to the destruction of infected trees, which are environmentally hazardous and cost-prohibitive for growers, respectively. A major limitation to combating HLB is the inability to isolate CLas in axenic culture, which hinders in vitro studies and creates a need for robust in situ CLas detection and visualization methods. The aim of this study was to investigate the efficacy of a nutritional program-based approach for HLB treatment, and to explore the effectiveness of an enhanced immunodetection method to detect CLas-infected tissues. To achieve this, four different biologically enhanced nutritional programs (bENPs; P1, P2, P3, and P4) were tested on CLas-infected citrus trees. Structured illumination microscopy preceded by a modified immunolabeling process and transmission electron microscopy were used to show treatment-dependent reduction of CLas cells in phloem tissues. No sieve pore plugging was seen in the leaves of P2 trees. This was accompanied by an 80% annual increase in fruit number per tree and 1,503 (611 upregulated and 892 downregulated) differentially expressed genes. These included an MLRQ subunit gene, UDP-glucose transferase, and genes associated with the alpha-amino linolenic acid metabolism pathway in P2 trees. Taken together, the results highlight a major role for bENPs as a viable, sustainable, and cost effective option for HLB management.Immediate accessThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

First report of Neodidymelliopsis ranunculi causing foliar black spot on citrus leaves in orchards of Algeria

During pest and disease surveys in summer 2017, severe leaf drops were observed in four citrus orchards, two sweet orange (cvs Thompson Navel and Washington Navel) and two mandarin (cvs Nova and Oro Grande) or-chards, located in Chlef, one of the most important citrus region in Algeria. Visual inspection of green dropped leaves and leaves on tree canopy revealed unusual symptoms consisting of greasy black protuberant spots on the abaxial side and yellowing on the adaxial surface. A quick survey was conducted to determine the incidence of the disease. The proportions of trees affected by the disease were 50 and 35% for the sweet orange and mandarin orchards, respectively. The incidence of the diseased leaves ranged from 30 to 60% for sweet orange, while 50-70% of leaves were symptomatic in the mandarin orchards. Morphological identification and a multi-locus sequencing approach associated this disease to the fungus Neodidymelliopsis ranunculi. Koch's postulates also confirmed N. ranunculi to be the causal agent. This is the first report of black spot symptoms caused by N. ranunculi on citrus in Algeria. The rapid spread of the disease since its first detection, poses a serious threat to the sustainability of citrus production in Algeria and calls for the implementation of urgent management actions