Showing papers in "Annals of Applied Biology in 2021"
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TL;DR: In this article, the role of the hypersensitive response threshold during infection by biotrophic, necrotrophic and hemibiotrophic pathogens and the impact in plant fitness and the community of pathogens found in the environment is discussed.
Abstract: A wide range of potentially plant pathogenic microorganisms are naturally present in the environment. Despite relying only on the innate immune system, plants are able to resist most of the pathogens. Plants employ a multi‐layered defence system in which the first layer triggers the basal resistance (pathogen‐associated molecular pattern‐triggered immunity [PTI]). The second layer occurs when a resistance protein (R protein) that mostly encodes nucleotide‐binding leucine‐rich repeat receptors (NLRs) recognises an effector molecule secreted by an adapted pathogen, leading to effector‐triggered immunity (ETI), which triggers the hypersensitive response (HR). More recently, ETI was shown to restore and potentiate PTI signalling components, leading to a robust immune response. Multiple mechanisms of regulation are employed to guarantee proper HR activation. NLR proteins can interact between them and form a heel‐like pentamer that anchors to the plasma membrane. Furthermore, NLRs and other proteins can cooperate with NLRs to propagate the immune signalling. Downstream to the recognition of the pathogen by the plant, a rapid cellular response is initiated involving the generation of signalling events that precedes the HR. Here, we summarise the mechanisms involved in HR and highlight new advances in the knowledge of the immune system signalling. We also approach the role of HR threshold during infection by biotrophic, necrotrophic and hemibiotrophic pathogens and the impact in plant fitness and the community of pathogens found in the environment.
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TL;DR: An evolutionary pathway is proposed in which a series of gene duplications gave rise to the five genes found in modern Triticeae species, suggesting that the hybridisation event that gave Rise to hexaploid bread wheat occurred more than once.
Abstract: Asparagine synthetase catalyses the transfer of an amino group from glutamine to aspartate to form glutamate and asparagine. The accumulation of free (non-protein) asparagine in crops has implications for food safety because free asparagine is the precursor for acrylamide, a carcinogenic contaminant that forms during high-temperature cooking and processing. Here we review publicly-available genome data for asparagine synthetase genes from species of the Pooideae subfamily, including bread wheat and related wheat species (Triticum and Aegilops spp.), barley (Hordeum vulgare) and rye (Secale cereale) of the Triticeae tribe. Also from the Pooideae subfamily: brachypodium (Brachypodium dystachion) of the Brachypodiae tribe. More diverse species are also included, comprising sorghum (Sorghum bicolor) and maize (Zea mays) of the Panicoideae subfamily, and rice (Oryza sativa) of the Ehrhartoideae subfamily. The asparagine synthetase gene families of the Triticeae species each comprise five genes per genome, with the genes assigned to four groups: 1, 2, 3 (subdivided into 3.1 and 3.2) and 4. Each species has a single gene per genome in each group, except that some bread wheat varieties (genomes AABBDD) and emmer wheat (Triticum dicoccoides; genomes AABB) lack a group 2 gene in the B genome. This raises questions about the ancestry of cultivated pasta wheat and the B genome donor of bread wheat, suggesting that the hybridisation event that gave rise to hexaploid bread wheat occurred more than once. In phylogenetic analyses, genes from the other species cluster with the Triticeae genes, but brachypodium, sorghum and maize lack a group 2 gene, while rice has only two genes, one group 3 and one group 4. This means that TaASN2, the most highly expressed asparagine synthetase gene in wheat grain, has no equivalent in maize, rice, sorghum or brachypodium. An evolutionary pathway is proposed in which a series of gene duplications gave rise to the five genes found in modern Triticeae species.
TL;DR: This study provides an update to the distribution of CMBs in SW and NC Nigeria and will be useful in development of monitoring and management strategies for the disease in both regions.
Abstract: Cassava mosaic disease (CMD), caused by cassava mosaic begomoviruses (CMBs), is a major threat to cassava production in Nigeria. The predominant CMBs in Nigeria are African cassava mosaic virus (ACMV), East African cassava mosaic virus (EACMV) and East African cassava mosaic Cameroon virus (EACMCV), which are transmitted through infected stem cuttings and whitefly vectors. This study was conducted in 2015 and 2017 to assess the epidemiology of CMD and the current distribution of CMBs in cassava farms in South West (SW) and North Central (NC) Nigeria. A survey of cassava farms was undertaken, and samples representative of disease symptoms were collected and assessed using molecular techniques. A total of 184 and 328 cassava farms were sampled in 2015 and 2017, respectively. CMD incidence for both regions surveyed was 43.80 and 12.25% in 2015 and 2017, respectively. Fields in SW recorded a higher incidence rate in 2015 (SW: 45.11%, NC: 42.47%), while the reverse occurred in 2017 (SW: 10.90%, NC: 14.01%). Overall, the CMD incidence in Benue State (NC) was significantly higher than other locations surveyed in both years. CMD symptom severity and mean whitefly population were higher in SW Nigeria in the two survey years. ACMV was widespread across both zones, occurring in 79.1% (453/613) and 54.8% (386/704) of cassava leaf samples analysed in 2015 and 2017, respectively. EACMV was detected in only 6.0% (37/613) and 4.7% (33/704) of all cassava leaf samples analysed in 2015 and 2017, respectively. Overall, a higher proportion of infected samples were found in NC in both 2015 (NC: 85.2%, SW: 75.4%) and 2017 (NC: 73.6%, SW: 45.2%). Detection using strain-specific primers revealed that 97% of EACMV positive samples were indeed infected by the EACMCV strain of the virus. As previously reported, samples with mixed infections showed a higher symptom severity than samples with single ACMV or EACMV infections. This study provides an update to the distribution of CMBs in SW and NC Nigeria and will be useful in development of monitoring and management strategies for the disease in both regions.
TL;DR: The current paper as mentioned in this paper augments the original BBCH scale, while retaining its structure and logic, and provides alternative and comprehensive descriptions of growth stages suitable for potato plants grown from different types of planting materials, and for all end uses of these plants.
Abstract: The recent invention of hybrid breeding technology for potato has led to an increased interest in hybrid potato R&D. Hybrid true potato seeds (TPS) are used to produce planting materials such as transplants and seedling tubers, but can also be used for direct seeding of seed or ware crops. Transplants and seedling tubers can be used to produce seed tubers or ware tubers. The rise in R&D in hybrid breeding creates the need for phenological scales of growth and development of plants produced by the various planting material types of hybrid-TPS. The BBCH (Biologische Bundesanstalt, Bundessortenamt and CHemical Industry) scale is one of the phenological scales developed for the description of the growth and development stages of plants. In 1993, a BBCH scale with descriptions for potato plants was released. The original BBCH scale gave standardised descriptions for TPS- and tuber-grown plants. Differences in the morphology of plants originating from the different planting materials in terms of types of branches and differences in below-ground growth and development were not included. Moreover, for reproductive growth stages, crucial for hybrid breeding, the original scale is incomplete as it does not carefully take the complex sympodial branching into account. Methods of describing growth of tubers and berries are complex and impossible to use when final tuber mass or berry size is unknown. The current paper augments the original BBCH scale, while retaining its structure and logic. It provides alternative and comprehensive descriptions of growth stages suitable for potato plants grown from different types of planting materials, and for all end uses of these plants. The proposed scale is detailed enough for research and breeding but still general enough for agricultural use.
TL;DR: In the context of the bovine spongiform encephalopathy (BSE) epidemic in 1986 highlighted the importance of the rendering industry as a key component of the food supply chain this article.
Abstract: The bovine spongiform encephalopathy (BSE) epidemic in 1986 highlighted the importance of the rendering industry as a key component of the food supply chain. Prior to 1986 the rendering industry was poorly understood. However, following the emergence of BSE research was commissioned to characterise rendering systems and investigate their ability to inactivate transmissible spongiform encephalopathy (TSE) agents. Six rendering systems were found to be operational in Europe but their key process parameters, such as particle size, process temperature and transit time, were poorly characterised. This review describes how these key process parameters were determined and used to inform protocols for the subsequent TSE inactivation trials which subsequently shaped both EU legislation and the development of techniques used to validate rendering systems. It also describes how EU legislation banning the use of animal‐derived proteins in animal feeds ('feed ban') effectively eliminated the market for meat and bone meal (MBM) and how the rendering industry sought to 'add value' to rendered products by conducting research to support the development of new markets for rendered products. The nutritional, environmental and economic characteristics of modern processed animal proteins (PAPs) mean that they represent valuable ingredients for use in animal feeds. Recent research has paved the way for legislative changes allowing the safe reintroduction of nonruminant PAP into aqua‐feeds and may soon facilitate their reintroduction into pig and poultry feeds. However, resistance from key stakeholders in the food chain remains a significant challenge that must be overcome before their full potential can be realised. Further research is required to characterise modern PAPS and to ensure their appropriate, safe and acceptable inclusion in animal feeds.
TL;DR: Surprisingly, tuber size distribution was more dependent on irrigation management than on soil strength, and the role of hormonal signalling in regulating tuber growth when plants are exposed to compact and dry soils is still poorly understood.
Abstract: Compact and dry soils impede root growth and restrict plant water availability, respectively, potentially causing leaf water deficit. Although both stresses likely co-occur in the field and limit yield, little is known about their combined impact on plant growth and physiology over a whole season, especially in a tuberous crop like potato. Field-grown potato (Solanum tuberosum L. var. 'Maris Piper') was exposed to factorial combination of deficit irrigation (watering when soil moisture deficit reached 60 vs. 25 mm) and soil compaction (compacted with heavy machinery vs. uncompacted), with plant growth and leaf physiology measured weekly. Shoot growth was restricted by adverse soil conditions, while leaf water status, photosynthesis rates and leaf abscisic acid (ABA) levels did not vary significantly between treatments. Across all treatments, final yield was linearly correlated (R2 = 0.71) to mid-season shoot biomass. Compared to well-watered plants growing in loose soil, soil compaction, deficit irrigation and their combination decreased final tuber yield similarly, by 23%–34%. Surprisingly, tuber size distribution was more dependent on irrigation management than on soil strength. Plants exposed to deficit irrigation produced more, smaller potatoes than their respective control. Thus, low soil water availability and/or compact soil caused these field-grown potatoes to restrict shoot growth rather than limit leaf gas exchange. Further research is needed to understand the role of hormonal signalling in regulating tuber growth when plants are exposed to compact and dry soils. © 2021 The Authors. Annals of Applied Biology published by John Wiley & Sons Ltd on behalf of Association of Applied Biologists.
TL;DR: In this article, the authors evaluated the response of sunflower seeds to drought in the germination stage, and established strong effects of the imposed drought stress and the metabolic response to oxidative stress through lower germinability and proline accumulation in seedlings.
Abstract: © 2020 Association of Applied Biologists Sunflower seeds (hybrid Luka) were primed with water (hydropriming) or sodium hydrosulphide (NaHS) solutions (0.1, 0.5, 1.0 and 1.5 mM NaHS) and subsequently dried to initial moisture content. Unprimed (control) and primed seeds were germinated in a growth chamber on paper towels moistened with water or polyethylene glycol (PEG) 6000 solutions (2.5, 5.0 and 10%), mimicking different drought stress levels. To evaluate the response of the primed seeds to drought in the germination stage, the germination energy (GE), germination rate (SG), seedling fresh mass (SW), hydrogen peroxide and free proline content (PRO), as well as lipid peroxidation rate (malondialdehyde; MDA) were established. The results show strong effects of the imposed drought stress and the metabolic response to oxidative stress through lower germinability and proline accumulation in seedlings. NaHS priming showed some positive effects on seed germination depending on stress level and the concentration of NaHS. Sunflower seeds were also germinated in pots filled with soil, at optimal (70% of field water capacity [FWC 70%]) and drought conditions (FWC 30%), in natural outdoors conditions. When plantlets developed the first pair of leaves, the number of plants (emergence rate [ER]), shoot mass (SM) and leaves mass (LM) were determined, as well as the total activities of catalase (CAT), ascorbate peroxidase (APX), glutathione reductase (GR) and dehydroascorbate reductase (DHAR). There was a significant influence of an interaction between drought stress and priming, whereas drought stress inhibited plant emergence and early growth (SW and LW), and strong antioxidative enzymatic response to drought stress was clearly established in the leaves. Although seed priming showed some influence on enzyme activities, it was mostly related to seed hydropriming effects, while NaHS seed priming was less effective, influencing only DHAR. Altogether, the results imply that sunflower seed priming with NaHS may not have a prolonged impact on the antioxidative defence mechanism based on CAT and ascorbate/glutathione cycle during sunflower early growth in drought conditions.
TL;DR: In this paper, la editorial tiene los derechos de autor y le solicito a hacer visibles la fecha tecnica del articulo. Butte et al.
Abstract: La editorial tiene los derechos de autor y le solicito a hacer visibles la fecha tecnica del articulo.