CERES :: Browsing by Author "Thompson, Andrew J."

Browsing by Author "Thompson, Andrew J."

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Open Access
Abscisic acid acts essentially on stomata, not on xylem, to improve drought resistance in tomato
(Wiley, 2023-08-01) Haverroth, Eduardo J.; Oliveira, Leonardo A.; Andrade, Moab T.; Taggart, Matthew; McAdam, Scott A. M.; Zsögön, Agustin; Thompson, Andrew J.; Martins, Samuel C. V.; Cardoso, Amanda A.
Drought resistance is essential for plant production under water-limiting environments. Abscisic acid (ABA) plays a critical role in stomata but its impact on hydraulic function beyond the stomata is far less studied. We selected genotypes differing in their ability to accumulate ABA to investigate its role in drought-induced dysfunction. All genotypes exhibited similar leaf and stem embolism resistance regardless of differences in ABA levels. Their leaf hydraulic resistance was also similar. Differences were only observed between the two extreme genotypes: sitiens (sit; a strong ABA-deficient mutant) and sp12 (a transgenic line that constitutively overaccumulates ABA), where the water potential inducing 50% embolism was 0.25 MPa lower in sp12 than in sit. Maximum stomatal and minimum leaf conductances were considerably lower in plants with higher ABA (wild type [WT] and sp12) than in ABA-deficient mutants. Variations in gas exchange across genotypes were associated with ABA levels and differences in stomatal density and size. The lower water loss in plants with higher ABA meant that lethal water potentials associated with embolism occurred later during drought in sp12 plants, followed by WT, and then by the ABA-deficient mutants. Therefore, the primary pathway by which ABA enhances drought resistance is via declines in water loss, which delays dehydration and hydraulic dysfunction.
Open Access
Automatic detection of regions in spinach canopies responding to soil moisture deficit using combined visible and thermal imagery
(Public Library of Science (PLoS), 2014-06-03T00:00:00Z) Raza, Shan-e-Ahmed; Smith, Hazel K.; Clarkson, Graham J. J.; Taylor, Gail; Thompson, Andrew J.; Clarkson, John; Rajpoot, Nasir M.
Thermal imaging has been used in the past for remote detection of regions of canopy showing symptoms of stress, including water deficit stress. Stress indices derived from thermal images have been used as an indicator of canopy water status, but these depend on the choice of reference surfaces and environmental conditions and can be confounded by variations in complex canopy structure. Therefore, in this work, instead of using stress indices, information from thermal and visible light imagery was combined along with machine learning techniques to identify regions of canopy showing a response to soil water deficit. Thermal and visible light images of a spinach canopy with different levels of soil moisture were captured. Statistical measurements from these images were extracted and used to classify between canopies growing in well-watered soil or under soil moisture deficit using Support Vector Machines (SVM) and Gaussian Processes Classifier (GPC) and a combination of both the classifiers. The classification results show a high correlation with soil moisture. We demonstrate that regions of a spinach crop responding to soil water deficit can be identified by using machine learning techniques with a high accuracy of 97%. This method could, in principle, be applied to any crop at a range of scales.
Open Access
BIFURCATE FLOWER TRUSS: a novel locus controlling inflorescence branching in tomato contains a defective MAP kinase gene
(Oxford University Press, 2018-03-02) Silva Ferreira, Demetryus; Kevei, Zoltan; Kurowski, Tomasz J.; de Noronha Fonseca, Maria Esther; Mohareb, Fady R.; Boiteux, Leonardo S.; Thompson, Andrew J.
A mutant line, bifurcate flower truss (bif), was recovered from a tomato breeding program. Plants from the control line LAM183 produced a mean of 0.16 branches per truss, whereas the value for bif plants was 4.1. This increase in branching was accompanied by a 3.3-fold increase in flower number and showed a significant interaction with exposure to low temperature during truss development. The LAM183 and bif genomes were resequenced and the bif gene was mapped to a 2.01 Mbp interval on chromosome 12; all coding region polymorphisms in the interval were surveyed and five candidate genes displaying altered protein sequences were detected. One of these genes, SlMAPK1, encoding a MAP kinase, contained a leucine-to-stop codon mutation predicted to disrupt kinase function. SlMAPK1 is an excellent candidate for bif because knock-out mutations of an Arabidopsis orthologue MPK6 were reported to have increased flower number. An introgression browser was used to demonstrate that the origin of the bif genomic DNA at the BIF locus was Solanum galapagense and that the SlMAPK1 null mutant is a naturally occurring allele widespread only on the Galápagos Islands. This work strongly implicates SlMAPK1 as part of the network of genes controlling inflorescence branching in tomato.
Open Access
Biochemical characterization and selective inhibition of β-carotene cis-trans isomerase D27 and carotenoid cleavage dioxygenase CCD8 on the strigolactone biosynthetic pathway
(Wiley, 2015-08-31) Harrison, Peter J.; Newgas, Sophie A.; Decombes, Flora; Shepherd, Sarah A.; Thompson, Andrew J.; Bugg, Timothy D. H.
The first three enzymatic steps of the strigolactone biosynthetic pathway catalysed by β-carotene cis-trans isomerase Dwarf27 (D27) from Oryza sativa and carotenoid cleavage dioxygenases CCD7 and CCD8 from Arabidopsis thaliana have been reconstituted in vitro, and kinetic assays have been developed for each enzyme, in order to develop selective enzyme inhibitors. Recombinant OsD27 shows a UV-visible λ at 422 nm and is inactivated by silver(I) acetate, consistent with the presence of an iron-sulfur cluster that is used in catalysis. OsD27 and AtCCD7 are not inhibited by hydroxamic acids that cause shoot branching in planta, but OsD27 is partially inhibited by terpene-like hydroxamic acids. The reaction catalysed by AtCCD8 is shown to be a two-step kinetic mechanism using pre-steady-state kinetic analysis. Kinetic evidence is presented for acid-base catalysis in the CCD8 catalytic cycle and the existence of an essential cysteine residue in the CCD8 active site. AtCCD8 is inhibited in a time-dependent fashion by hydroxamic acids D2, D4, D5 and D6 (> 95% inhibition at 100 μm) that cause a shoot branching phenotype in A. thaliana, and selective inhibition of CCD8 is observed using hydroxamic acids D13H and D15 (82%, 71% inhibition at 10 μm). The enzyme inhibition data imply that the biochemical basis of the shoot branching phenotype is due to inhibition of CCD8.
Open Access
A bioinformatics and genotyping approach exploring personalised nutrition.
(Cranfield University, 2021-11) Molitor, Corentin; Mohareb, Fady R.; Thompson, Andrew J.
Personalised nutrition is at its early stages but shows the potential of improving the health of the general population, at a time when diabetes and obesity are becoming worldwide epidemics. However, it will need to be based on rigorous scientific research, as well as being accompanied by public policies and ethical considerations. Research is making great progress towards the understanding of the impact of genetics on complex diseases, which involve hundreds, or thousands, of variants, each having varying effect on the disease. Personalised medicine aims at harnessing this genetic information to tailor prevention and treatment according to each individual. Unfortunately, the links between the genotype and the phenotype are not yet fully understood. And while the content of publicly available genetic databases is exponentially growing, they are often using different formats and means of access, making it difficult to get complete information. Moreover, evaluating the genetic predisposition of an individual to a disease is not straightforward, and while Polygenic Risk Score models can help in this regard, they are often only based on common variants, which might lead to misevaluation of the risk for rare- variants carriers. In this thesis will be presented (i) VarGen, an R package to merge information from different genetic databases, which has the potential to infer new variant- disease relationships. (ii) a new method to improve Polygenic Risk Score models, which includes variants obtained from VarGen on top of the common variants from standard polygenic analyses. (iii) the results of a microRNA differential expression analysis, aiming at identifying the impact of microRNAs, on the development of severe Hypoxic-Ischemic Encephalopathy in new-borns.
Open Access
Chapter 3: Rootstock breeding: current practices and future technologies
(CAB eBooks, 2017-01-31) Thompson, Andrew J.; Belen Pico, Maria; Yetişir, Halit; Cohen, Roni; Bebeli, Penelope J.
This chapter explores how genetic diversity can be exploited more deeply to create new rootstock cultivars, and describes the current and future breeding strategies applicable to rootstocks. It considers how to combine different sources of genetic variation, for example by overcoming species barriers, and how to select useful rootstocks. The many traits that can be associated with the root system or conferred by a rootstock to the scion are outlined. The impact of the practice of grafting on breeding strategies is also discussed.
Open Access
A chromosome-level genome assembly of Solanum chilense, a tomato wild relative associated with resistance to salinity and drought
(Frontiers, 2024-03-08) Molitor, Corentin; Kurowski, Tomasz J.; Fidalgo de Almeida, Pedro M.; Kevei, Zoltan; Spindlow, Daniel J.; Chacko Kaitholil, Steffimol R.; Iheanyichi, Justice U.; Prasanna, H. C.; Thompson, Andrew J.; Mohareb, Fady R.
Introduction: Solanum chilense is a wild relative of tomato reported to exhibit resistance to biotic and abiotic stresses. There is potential to improve tomato cultivars via breeding with wild relatives, a process greatly accelerated by suitable genomic and genetic resources. Methods: In this study we generated a high-quality, chromosome-level, de novo assembly for the S. chilense accession LA1972 using a hybrid assembly strategy with ~180 Gbp of Illumina short reads and ~50 Gbp long PacBio reads. Further scaffolding was performed using Bionano optical maps and 10x Chromium reads. Results: The resulting sequences were arranged into 12 pseudomolecules using Hi-C sequencing. This resulted in a 901 Mbp assembly, with a completeness of 95%, as determined by Benchmarking with Universal Single-Copy Orthologs (BUSCO). Sequencing of RNA from multiple tissues resulting in ~219 Gbp of reads was used to annotate the genome assembly with an RNA-Seq guided gene prediction, and for a de novo transcriptome assembly. This chromosome-level, high-quality reference genome for S. chilense accession LA1972 will support future breeding efforts for more sustainable tomato production. Discussion: Gene sequences related to drought and salt resistance were compared between S. chilense and S. lycopersicum to identify amino acid variations with high potential for functional impact. These variants were subsequently analysed in 84 resequenced tomato lines across 12 different related species to explore the variant distributions. We identified a set of 7 putative impactful amino acid variants some of which may also impact on fruit development for example the ethylene-responsive transcription factor WIN1 and ethylene-insensitive protein 2. These variants could be tested for their ability to confer functional phenotypes to cultivars that have lost these variants.
Open Access
Control of water-use efficiency by florigen
(Wiley, 2019-11-05) Robledo, Jessenia M.; Medeiros, David; Vicente, Mateus H.; Azevedo, Aristéa A.; Thompson, Andrew J.; Peres, Lázaro E. P.; Ribeiro, Dimas M.; Araújo, Wagner L.; Zsögön, Agustin
A major issue in modern agriculture is water loss through stomata during photosynthetic carbon assimilation. In water‐limited ecosystems, annual plants have strategies to synchronize their growth and reproduction to the availability of water. Some species or ecotypes of flowers are early to ensure that their life cycles are completed before the onset of late season terminal drought (“drought escape”). This accelerated flowering correlates with low water‐use efficiency (WUE). The molecular players and physiological mechanisms involved in this coordination are not fully understood. We analyzed WUE using gravimetry, gas exchange, and carbon isotope discrimination in florigen deficient (sft mutant), wild‐type (Micro‐Tom), and florigen over‐expressing (SFT‐ox) tomato lines. Increased florigen expression led to accelerated flowering time and reduced WUE. The low WUE of SFT‐ox was driven by higher stomatal conductance and thinner leaf blades. This florigen‐driven effect on WUE appears be independent of abscisic acid (ABA). Our results open a new avenue to increase WUE in crops in an ABA‐independent manner. Manipulation of florigen levels could allow us to produce crops with a life cycle synchronized to water availability.
Open Access
The effects of controlled atmosphere and ethylene on the postharvest quality of sweet potato during storage.
(2018-04) Sowe, Sulaiman; Terry, Leon A.; Thompson, Andrew J.
Sweet potato (Ipomoea batatas Lam) is the third most important food commodity in Sierra Leone and global demand for the commodity is growing. To meet this demand requires the use of effective storage methods due to the perishability (shrivelling, sprouting and disease) of the root after harvest. This study therefore investigated the efficacy of controlled atmosphere (CA) and ethylene on the physiological, biochemical, mycological and molecular dynamics of sweet potato during storage. This was done by storing sweet potato samples (cultivar: 06-52; known as Belle Vue in the USA) at 20˚C as follows: CA (5 kPa CO₂ and 8 kPa O₂), air (0.003 kPa CO₂ and 21 kPa O₂), CA supplemented with 0.001 kPa ethylene and continuous exogenous ethylene (0.001 kPa) for a maximum of 12 weeks. A transition phase was established at six weeks of storage which involved swapping of treatments from CA with and without supplemented ethylene to air storage and vice versa (Experiment 2) and that from ethylene to air storage and vice versa (Experiment 4). Results showed that in as much as the ethylene supplementation was successful in supressing sprouting, the contents of phenolics and sugars increased as well as weight loss and respiration rates, which undermine its positive aspects. Storage in CA reduced weight loss and respiration rates but did suppress sprouting as well. The complete inhibition of sprouting during storage could also be attributed to decreased biosynthesis of the cytokinin, trans-zeatine riboside (trans-ZR) in the sweet potato due to ethylene supplementation. Also ethylene induced rise in phenolics corresponded with an increased relative expression of ethylene response factors (ERF) in the proximal section unlike the reducing sugars. The ERF gene was more expressed towards the end of storage whilst ethylene insensitive 2 (EIN2) was more expressed at the beginning which suggested that EIN2 was actively repressed during storage particularly under CA treatment. Furthermore, continuous CA storage was effective in mitigating disease development on the sweet potato as well as in controlling Penicillium development but not that of Fusarium. Major diseases identified on the sweet potato were Fusarium surface rot and Rhizopus soft rot predominantly at the proximal and distal sections mainly during storage under ethylene supplemented CA. The mycotoxin, aflatoxin G1 was the most predominant potentially produced aflatoxin on the sweet potato and continuous CA was very effective in inhibiting the potential contamination of all the studied aflatoxins: aflatoxin B1 (AFB1), aflatoxin B2 (AFB2) and aflatoxin G1 (AFG1) during storage.
Open Access
Elevated CO2 and high endogenous ABA level alleviate PEG-induced short-term osmotic stress in tomato plants
(Elsevier, 2021-12-18) Li, Shenglan; Wang, Xizi; Liu, Xiaojuan; Thompson, Andrew J.; Liu, Fulai
Elevated CO2 concentration (e[CO2]) alleviates the impact of drought stress on plants where abscisic acid (ABA) is involved. To explore the mechanisms by which tomato plants respond to short-term osmotic stress, Solanum lycopersicum cv. Ailsa Craig (AC), a transgenic line overproducing ABA (sp5), and an ABA-deficient mutant (flacca) were hydroponically grown under ambient CO2 (400 ppm) and e[CO2] (800 ppm) and then exposed to 10% or 15% (w/v) polyethylene glycol (PEG) 6000 for 24 h before transferring to PEG-free nutrient solution for 24 h. Under non-stress condition, e[CO2] decreased root hydraulic conductance (Kroot), which was overridden by high endogenous ABA in sp5 through increasing specific leaf area and root branching intensity. Basically, e[CO2] improved stress resistance through enhanced water status. PEG stress decreased stomatal conductance and osmotic potential in AC but these effects were less pronounced in sp5, which exhibited a stronger osmotic adjustment (OA) and improved plant fitness. A greater flexibility of hydraulic system and a reduced sensitivity of Kroot to ABA might confer sp5 a great ability to recover from PEG stress. On the contrary, high stomatal density, size and pore aperture of flacca rendered plants suffering severe stress. Moreover, the premise that PEG stress could mimic soil water deficit was the sufficient achievement of OA. Our results indicate that e[CO2] and high endogenous ABA level could improve osmotic stress resistance in tomato plants via osmotic and hydraulic adjustments.
Open Access
Environmental, developmental, and genetic factors controlling root system architecture
(Taylor & Francis, 2014-12-31) Mansoorkhani, F. M.; Seymour, G. B.; Swarup, R.; Moeiniyan Bagheri, H.; Ramsey, R. J. L.; Thompson, Andrew J.
A better understanding of the development and architecture of roots is essential to develop strategies to increase crop yield and optimize agricultural land use. Roots control nutrient and water uptake, provide anchoring and mechanical support and can serve as important storage organs. Root growth and development is under tight genetic control and modulated by developmental cues including plant hormones and the environment. This review focuses on root architecture and its diversity and the role of environment, nutrient, and water as well as plant hormones and their interactions in shaping root architecture.
Open Access
Ethylene and 1-methylcyclopropene differentially regulate gene expression during onion sprout suppression.
(American Society of Plant Biologists, 2011-07-31T00:00:00Z) Cools, Katherine; Chope, Gemma Amy; Hammond, John P.; Thompson, Andrew J.; Terry, Leon A
Onion (Allium cepa) is regarded as a nonclimacteric vegetable. In onions, however, ethylene can suppress sprouting while the ethylene-binding inhibitor 1- methylcyclopropene (1-MCP) can also suppress sprout growth; yet, it is unknown how ethylene and 1-MCP elicit the same response. In this study, onions were treated with 10 μL L(-1) ethylene or 1 μL L(-1) 1-MCP individually or in combination for 24 h at 20°C before or after curing (6 weeks) at 20°C or 28°C and then stored at 1°C. Following curing, a subset of these same onions was stored separately under continuous air or ethylene (10 μL L(-1)) at 1°C. Onions treated with ethylene and 1-MCP in combination after curing for 24 h had reduced sprout growth as compared with the control 25 weeks after harvest. Sprout growth following storage beyond 25 weeks was only reduced through continuous ethylene treatment. This observation was supported by a higher proportion of down- regulated genes characterized as being involved in photosynthesis, measured using a newly developed onion microarray. Physiological and biochemical data suggested that ethylene was being perceived in the presence of 1-MCP, since sprout growth was reduced in onions treated with 1-MCP and ethylene applied in combination but not when applied individually. A cluster of probes representing transcripts up-regulated by 1-MCP alone but down-regulated by ethylene alone or in the presence of 1-MCP support this suggestion. Ethylene and 1-MCP both down- regulated a probe tentatively annotated as an ethylene receptor as well as ethylene-insensitive 3, suggesting that both treatments down-regulate the perception and signaling events of e
Open Access
Fructans redistribution prior to sprouting in stored onion bulbs is a potential marker for dormancy break
(Elsevier, 2018-12-18) Ohanenye, Ikenna Christian; Alamar, M Carmen; Thompson, Andrew J.; Terry, Leon A
Continuous supply of high quality onion bulbs to meet year-round demand is dependent on maintaining dormancy and bulb quality during storage. Sprouting impacts negatively on the storage quality of onion bulbs. Ethylene supplementation has previously been revealed to inhibit sprout growth in stored onion bulbs. Fructans content, especially those at higher degree of polymerisation (DP), are reported to positively correlate with delayed sprouting. However, little is known about the impact of pre-harvest irrigation regimes on fructans accumulation and redistribution in relation to onion bulb dormancy and quality in store. Across two seasons, onion plants of cultivars ‘Red Baron’ and ‘Sherpa’ were subjected to full irrigation (FI) (100% replenishment of crop evapotranspiration) or deficit irrigation (DI) (50% of FI treatment) from bulb initiation to harvest. Bulbs were harvested at full maturity and stored at 1 °C for five months. Bulbs were treated with or without 1-MCP (1 μL L−1) for 24 h before storage under continuous ethylene supplementation (10 μL L−1) or air. DI had no effect on dormancy-break, sprout emergence, total fructans content and total sugar content. In contrast, ethylene delayed sprout emergence and suppressed sprout growth; added 1-MCP enhanced this effect. The concentration of DP3-8 fructans were higher in top and bottom sections compared to the baseplate. Before sprout emergence, fructans of DPs 7–8 were no longer present in the top and bottom wedges, while they accumulated in the baseplate; irrespective of pre- or postharvest treatments. This redistribution of fructans within the bulb suggested a transition in dormancy state and could be used as a predictive marker for sprouting in stored onion bulbs.
Open Access
Genes involved in auxin biosynthesis, transport and signalling underlie the extreme adventitious root phenotype of the tomato aer mutant
(Springer, 2024-03-03) Kevei, Zoltan; Larriba, Eduardo; Romero‑Bosquet, María Dolores; Nicolás‑Albujer, Miriam; Kurowski, Tomasz J.; Mohareb, Fady; Rickett, Daniel; Pérez‑Pérez, José Manuel; Thompson, Andrew J.
The use of tomato rootstocks has helped to alleviate the soaring abiotic stresses provoked by the adverse effects of climate change. Lateral and adventitious roots can improve topsoil exploration and nutrient uptake, shoot biomass and resulting overall yield. It is essential to understand the genetic basis of root structure development and how lateral and adventitious roots are produced. Existing mutant lines with specific root phenotypes are an excellent resource to analyse and comprehend the molecular basis of root developmental traits. The tomato aerial roots (aer) mutant exhibits an extreme adventitious rooting phenotype on the primary stem. It is known that this phenotype is associated with restricted polar auxin transport from the juvenile to the more mature stem, but prior to this study, the genetic loci responsible for the aer phenotype were unknown. We used genomic approaches to define the polygenic nature of the aer phenotype and provide evidence that increased expression of specific auxin biosynthesis, transport and signalling genes in different loci causes the initiation of adventitious root primordia in tomato stems. Our results allow the selection of different levels of adventitious rooting using molecular markers, potentially contributing to rootstock breeding strategies in grafted vegetable crops, especially in tomato. In crops vegetatively propagated as cuttings, such as fruit trees and cane fruits, orthologous genes may be useful for the selection of cultivars more amenable to propagation.
Open Access
Guidelines to use tomato in experiments with a controlled environment
(Frontiers Media, 2014-11-18) Schwarz, Dietmar; Thompson, Andrew J.; Kläring, Hans-Peter
Domesticated tomato (Solanum lycopersicum) is the most important horticultural crop worldwide. Low polymorphism at the DNA level conflicts with the wealth of morphological variation. Fruits vary widely in size, shape, and color. In contrast, genetic variation between the 16 wild relatives is tremendous. Several large seed banks provide tomato germplasm for both domesticated and wild accessions of tomato. Recently, the genomes of the inbred cultivar “Heinz 1706” (≈900 Mb), and S. pimpinellifolium (739 Mb) were sequenced. Genomic markers and genome re-sequencing data are available for >150 cultivars and accessions. Transformation of tomato is relatively easy and T-DNA insertion line collections are available. Tomato is widely used as a model crop for fruit development but also for diverse physiological, cellular, biochemical, molecular, and genetic studies. It can be easily grown in greenhouses or growth chambers. Plants grow, flower, and develop fruits well at daily light lengths between 8 and 16 h. The required daily light integral of an experiment depends on growth stage and temperature investigated. Temperature must be 10–35°C, relative humidity 30–90%, and, CO2 concentration 200–1500 μmol mol−1. Temperature determines the speed of the phenological development while daily light integral and CO2 concentration affect photosynthesis and biomass production. Seed to seed cultivation takes 100 days at 20°C and can be shortened or delayed by temperature. Tomato may be cultivated in soil, substrates, or aeroponically without any substrate. Root volume, and water uptake requirements are primarily determined by transpiration demands of the plants. Many nutrient supply recipes and strategies are available to ensure sufficient supply as well as specific nutrient deficits/surplus. Using appropriate cultivation techniques makes tomato a convenient model plant for researchers, even for beginners.
Open Access
Identification of novel stress-responsive biomarkers from gene expression datasets in tomato roots
(CSIRO Publishing, 2016-05-17) Thompson, Andrew J.; Kevei, Zoltan
Abiotic stresses such as heat, drought or salinity have been widely studied individually. Nevertheless, in the nature and in the field, plants and crops are commonly exposed to a different combination of stresses, which often result in a synergistic response mediated by the activation of several molecular pathways that cannot be inferred from the response to each individual stress. By screening microarray data obtained from different plant species and under different stresses, we identified several conserved stress-responsive genes whose expression was differentially regulated in tomato (Solanum lycopersicum L.) roots in response to one or several stresses. We validated 10 of these genes as reliable biomarkers whose expression levels are related to different signalling pathways involved in adaptive stress responses. In addition, the genes identified in this work could be used as general salt-stress biomarkers to rapidly evaluate the response of salt-tolerant cultivars and wild species for which sufficient genetic information is not yet available.
Open Access
Identifying opportunities to improve management of water stress in banana production
(Elsevier, 2020-09-19) Panigrahi, Niranjan; Thompson, Andrew J.; Zubelzu, Sergio; Knox, Jerry W.
Banana (Musa spp.) is one of the most valuable global agricultural commodities, with commercial plantations responsible for supplying nearly 15 % of total global banana production. These plantations are underpinned by major infrastructural investments and a high dependence on fertilizer, pesticide and irrigation inputs. In contrast, smallholders and subsistence farmers often cultivate bananas for local markets with minimal inputs. Water stress due to increasing rainfall variability and competition for water resources are emerging as major production constraints for both commercial and smallholder production. Water stress-induced yield losses of up to 65 % have been reported due to loss in bunch weight even in moderate to low rainfall areas. Thus, investments in more efficient irrigation systems and water-saving technologies are being widely promoted to increase water productivity through improved scheduling to reduce drainage and runoff losses. This paper synthesises scientific and industry evidence on crop growth and development including root and shoot development, plant water relations, and yield response to water. It also critiques the importance of irrigation scheduling for maximising irrigation efficiency. New evidence to support the synchronization of irrigation with crop water demand to reduce environmental impacts is provided. High variability in crop water demand (1200–2690 mm per year) was found to be linked to cultivar choice, crop development cycle, and fluctuating conditions in environmental and edaphic factors. The findings confirm that irrigation should be scheduled at moderate levels of soil water deficit sufficient to promote deep and extensive rooting while maintaining banana quality. Management practices are recommended to mitigate water stress without compromising yield under limited rainfall and irrigation conditions. The ratooning cycle of banana also affects rooting activity and crop coefficients (Kc) compared to other annual crops. These aspects need to be considered when improving irrigation and crop modelling for banana. The findings provide valuable new insights and evidence for scientists and practitioners involved in banana research and management.
Open Access
Impact of overexpression of 9-cis-epoxycarotenoid dioxygenase on growth and gene expression under salinity stress
(Elsevier, 2019-09-12) Martínez-Andújar, Cristina; Martínez-Pérez, Ascensión; Ferrández-Ayela, Almudena; Albacete, Alfonso; Martínez-Melgarejo, Purificación A.; Dodd, Ian C.; Thompson, Andrew J.; Pérez, José Manuel; Pérez-Alfocea, Francisco
To better understand abscisic acid (ABA)’s role in the salinity response of tomato (Solanum lycopersicum L.), two independent transgenic lines, sp5 and sp12, constitutively overexpressing the LeNCED1 gene (encoding 9-cis-epoxycarotenoid dioxygenase, a key enzyme in ABA biosynthesis) and the wild type (WT) cv. Ailsa Craig, were cultivated hydroponically with or without the addition of 100 mM NaCl. Independent of salinity, LeNCED1 overexpression (OE) increased ABA concentration in leaves and xylem sap, and salinity interacted with the LeNCED1 transgene to enhance ABA accumulation in xylem sap and roots. Under control conditions, LeNCED1 OE limited root and shoot biomass accumulation, which was correlated with decreased leaf gas exchange. In salinized plants, LeNCED1 OE reduced the percentage loss in shoot and root biomass accumulation, leading to a greater total root length than WT. Root qPCR analysis of the sp12 line under control conditions revealed upregulated genes related to ABA, jasmonic acid and ethylene synthesis and signalling, gibberellin and auxin homeostasis and osmoregulation processes. Under salinity, LeNCED1 OE prevented the induction of genes involved in ABA metabolism and GA and auxin deactivation that occurred in WT, but the induction of ABA signalling and stress-adaptive genes was maintained. Thus, complex changes in phytohormone and stress-related gene expression are associated with constitutive upregulation of a single ABA biosynthesis gene, alleviating salinity-dependent growth limitation.
Open Access
Improving the tea withering process using ethylene or UV-C
(American Chemical Society, 2021-11-05) Collings, Emma R.; Alamar, M. Carmen; Bogaerts Márquez, Maria; Kourmpetli, Sofia; Kevei, Zoltan; Thompson, Andrew J.; Mohareb, Fady; Terry, Leon A.
Using a combination of biochemical, transcriptomic, and physiological analyses, we elucidated the mechanisms of physical and chemical withering of tea shoots subjected to UV-C and ethylene treatments. UV-C irradiation (15 kJ m–2) initiated oxidation of catechins into theaflavins, increasing theaflavin-3-monogallate and theaflavin digallate by 5- and 13.2–4.4-fold, respectively, at the end of withering. Concomitantly, a rapid change to brown/red, an increase in electrolyte leakage, and the upregulation of peroxidases (viz. Px2, Px4, and Px6) and polyphenol oxidases (PPO-1) occurred. Exogenous ethylene significantly increased the metabolic rate (40%) and moisture loss (30%) compared to control during simulated withering (12 h at 25 °C) and upregulated transcripts associated with responses to dehydration and abiotic stress, such as those in the ethylene signaling pathway (viz. EIN4-like, EIN3-FBox1, and ERFs). Incorporating ethylene during withering could shorten the tea manufacturing process, while UV-C could enhance the accumulation of flavor-related compounds.
Open Access
In vitro assay and inhibition of 9-cis-epoxycarotenoid dioxygenase (NCED) from Solanum lycopersicum and Zea mays
(Elsevier, 2024) Harrison, Peter J.; Chandler, Jake; Thompson, Andrew J.; Bugg, Timothy D. H.
The article reports methods for the expression and assay of 9-cis-epoxycarotenoid cleavage dioxygenase (NCED), an enzyme involved in the biosynthesis of phytohormone abscisic acid in plants. A method for the preparation of the unstable substrate 9′-cis-neoxanthin from fresh spinach is described. The inhibition of Solanum lycopersicum NCED by a series of aryl hydroxamic acid inhibitors is illustrated, and inhibitors D2 and D4 are assayed against NCED isozymes from Zea mays.