scholarly journals Xylella fastidiosa and Drought Stress in Olive Trees: A Complex Relationship Mediated by Soluble Sugars

Biology ◽  
2022 ◽  
Vol 11 (1) ◽  
pp. 112
Author(s):  
Mariarosaria De Pascali ◽  
Marzia Vergine ◽  
Carmine Negro ◽  
Davide Greco ◽  
Federico Vita ◽  
...  

Xylella fastidiosa (Xf) subsp. pauca “De Donno” is the etiological agent of “Olive Quick Decline Syndrome” (OQDS) on olive trees (Olea europaea L.); the presence of the bacterium causes xylem vessel occlusions inducing a drought stress and the development of leaf scorch symptoms, which may be worsened by water shortage in summer. In order to evaluate how the two stress factors overlap each other, the carbohydrate content and the expression patterns of genes related to carbohydrate metabolism have been evaluated in two olive cvs trees (Cellina di Nardò, susceptible to Xf, and Leccino, resistant to Xf) reporting transcriptional dynamics elicited by Xf infection, drought, or combined stress (drought/Xf). In the Xf-susceptible Cellina di Nardò plants, Xf and its combination with drought significantly decrease total sugars compared to control (−27.0% and −25.7%, respectively). In contrast, the Xf-resistant Leccino plants show a more limited reduction in sugar content in Xf-positive conditions (−20.1%) and combined stresses (−11.1%). Furthermore, while the amount of glucose decreases significantly in stressed Cellina di Nardò plants (≈18%), an increase was observed in Leccino plants under drought/Xf combined stresses (+11.2%). An opposite behavior among cvs was also observed for sucrose, as an accumulation of the disaccharide was recorded in stressed Leccino plants (≈37%). The different response to combined stress by Xf-resistant plants was confirmed considering genes coding for the sucrose or monosaccharide transporter (OeSUT1, OeMST2), the cell wall or vacuolar invertase (OeINV-CW, OeINV-V), the granule-bound starch synthase I (OeGBSSI) and sucrose synthase (OeSUSY), with a higher expression than at least one single stress (e.g., ≈1-fold higher or more than Xf for OeMST2, OeINV-CW, OeINV-V, OeGBSSI). It is probable that the pathways involved in drought stress response induce positive effects useful for pathogen resistance in cv Leccino, confirming the importance of investigating the mechanisms of cross-talk of biotic and abiotic responses.

Plants ◽  
2019 ◽  
Vol 8 (11) ◽  
pp. 437 ◽  
Author(s):  
Mariarosaria De Pascali ◽  
Marzia Vergine ◽  
Erika Sabella ◽  
Alessio Aprile ◽  
Eliana Nutricati ◽  
...  

Due to global climate change, complex combinations of stresses are expected to occur, among which the interaction between pathogens and drought stress may have a significant effect on growth and yield. In this study, the Xylella fastidiosa (Xf)-resistant cultivar Leccino and the susceptible one Cellina di Nardò were subjected to (a) individual drought stress, (b) Xf infection and (c) combination of both stress conditions. Here we report the physiological response to stresses in water content in leaves and the modulation in the expression level of seven genes responsive to plant water status and pathogen infection. In Xf-resistant plants, higher expression levels are reported for genes belonging to ROS-scavenging systems and for genes involved in pathogen stress (pathogenesis-related, PR, and leucine-rich repeat genes, LRR-RLK). However, PR and LRR-RLK were not further induced by water deficit. Interestingly, the genes related to drought response (aquaporin, PIP2.1, dehydration responsive element binding, DREB, and dehydrin, DHN), which induction was higher in Cellina di Nardò compared to Leccino during drought stress, was poorly induced in Xf-susceptible plants when Xf occur. Conversely, DHN was induced by Xf presence in Leccino. These results were consistent with observations on water content. Indeed, response was similar in Leccino regardless kind of stress or combination, whereas a strong reduction was observed in Xf-susceptible plants infected by Xf or in presence of combined stresses. Thus, the reported findings indicate that resistance of Leccino to Xf could be linked to its lower resistance to water stress, probably leading to the activation of alternative defense pathways that support the plant in Xf response.


Plants ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 2279
Author(s):  
Pin-Hua Lin ◽  
Yun-Yang Chao

The purpose of this experiment is to study the effects of treatment with 90% (28.5% volumetric water content (VWC)), 75% (24% VWC), 50% (16% VWC), and 25% (8% VWC) of water requirements on the growth of two djulis (Chenopodium formosana Koidz) varieties (red: RP and yellow: OR) and one quinoa (Chenopodium quinoa Willd) varieties (PI). The results showed that drought stress (8% VWC) significantly reduced plant growth and relative water content, and increased H2O2 and MDA content in C. formosana and C. quinoa. The most significant increase in these parameters was detected in the OR variety. The antioxidant enzymes, such as SOD, APX, and GR activities of PI variety under drought treatment (8% VWC), are significantly increased, while GR activity of C. formosana also increased significantly. Additionally, C. formosana and PI variety remained at a stable AsA/DHA ratio, but the GSH/GSSG ratio decreased during drought treatment. Moreover, drought stress increased total soluble sugars and proline content in the PI variety. However, C. formosana proline content was extremely significantly enhanced, and only the OR variety increased the total soluble sugar content at the same time during the vegetative growth period. In summary, C. formosana and C. quinoa have different drought tolerance mechanisms to adapt to being cultivated and produced under severe drought conditions.


2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Yanling Zheng ◽  
Zhining Xia ◽  
Jianrong Wu ◽  
Huancheng Ma

Abstract Background Trees of Bombax ceiba L. could produce a large number of viable seeds in the dry-hot valleys. However, the seedling regeneration of the species is difficult in these areas as mild drought often occur repeatedly which might be followed by heat stress. However, how the repeated drought affects the subsequent drought and heat tolerance of B. ceiba is not clear. In this study, chlorophyll fluorescence, soluble sugar content and lipid metabolism were measured for the drought-treated seedlings and heat-treated seedlings with or without drought hardening. Results Neither the first nor third dehydration treatments affected the photosynthetic activity and soluble sugar content of B. ceiba seedlings. However, they differentially affected the fluidity of the local membranes and the levels of diacylglycerol and phosphatidic acid. Heat shock severely decreased the photosynthetic efficiency but drought priming reduced the effects of heat shock. Moreover, heat shock with or without drought priming had differential effects on the metabolism of soluble sugars and some lipids. In addition, the unsaturation level of membrane glycerolipids increased following heat shock for non-drought-hardened seedlings which, however, maintained for drought-hardened seedlings. Conclusions The results suggest that two cycles of dehydration/recovery can affect the metabolism of some lipids during the third drought stress and may enhance the heat tolerance of B. ceiba by adjusting lipid composition and membrane fluidity.


Author(s):  
Dehghanzadeh H ◽  
◽  
Adavi Z ◽  

Drought is one of the most important abiotic stresses and factors limiting the successful production of plant products worldwide and has adverse effects on plant growth and other metabolic processes. The role of exogenous individual or combined application of Silicon (Si) and Cycocel (CCC) (control, 3.6gL-1 Si, 210mgL-1 CCC, and 3.6gL-1 Si + 210mgL-1 CCC) on grain yield and some key physiological characteristics of wheat (Triticum aestivum L.) cv. Gascogen (drought-sensitive) and Aflak (drought-tolerant) was investigated under field water-stress conditions (100% and 40% field capacity). Drought stress caused a considerable reduction in biological yield, yield and yield components, relative water content and leaf water potential of both cultivars. Application of Si and CCC effectively improved these parameters in water-deficit treatments. Moreover, water-limited conditions markedly promoted the activities of key antioxidant enzymes including peroxidase, ascorbate peroxidase, catalase and superoxide dismutase as well as the levels of Malondialdehyde (MDA) and hydrogen peroxide (H2O2), while enhancing the accumulation of soluble sugars, potassium, magnesium and calcium in leaf tissues. Application of Si and CCC further enhanced the activities of the key antioxidant enzymes and accumulation of osmolytes, and decreased the levels of H2O2 and MDA in drought stressed plants; the positive effects of Si were greatest when it was applied with CCC. Synergistic effects of Si + CCC application on yield and physiological parameters were apparent compared with Si or CCC applied separately water-stress alleviation and yield improvement in the wheat cultivars by Si and CCC application was attributable to partly improved osmotic adjustment and antioxidant activity as well as to more favorable water status under stress conditions. Overall, Si and CCC application proved to have great potential in promoting grain yield of wheat in drought-prone areas.


PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9040
Author(s):  
Zilong Li ◽  
Akash Tariq ◽  
Kaiwen Pan ◽  
Corina Graciano ◽  
Feng Sun ◽  
...  

Intercropping may improve community stability and yield under climate change. Here, we set up a field experiment to evaluate the advantages of cultivating Z anthoxylum bungeanum with Capsicum annum, and Z. bungeanum with Glycine max as intercrops, compared with cultivating Z. bungeanum in monoculture. Effects of extreme drought stress conditions on morphological, physiological, and biochemical traits of the three crop species cultivated in the three contrasting planting systems were compared. Results showed that extreme drought conditions induced negative impacts on Z. bungeanum grown in monoculture, due to reduced growth and metabolic impairment. However, limited stomatal conductance, reduced transpiration rate (Tr), and increased water use efficiency, carotenoid content, catalase activity, and accumulation of soluble sugars in Z. bungeanum indicated its adaptive strategies for tolerance of extreme drought stress conditions. Compared with cultivation in monoculture, intercropping with C. annum had positive effects on Z. bungeanum under extreme drought stress conditions, as a result of improved crown diameter, leaf relative water content (LRWC), net photosynthetic rate, and proline content, while intercropping with G. max under extreme drought stress conditions increased net CO2 assimilation rates, LRWC, Tr, and superoxide dismutase (SOD) activity. In conclusion, Z. bungeanum has an effective defense mechanism for extreme drought stress tolerance. Intercropping with G. max enhanced this tolerance potential primarily through its physio-biochemical adjustments, rather than as a result of nitrogen fixation by G. max.


2018 ◽  
Vol 5 (03) ◽  
Author(s):  
ARADHNA KUMARI ◽  
IM KHAN ◽  
ANIL KUMAR SINGH ◽  
SANTOSH KUMAR SINGH

Poplar clone Kranti was selected to assess the morphological, physiological and biochemical responses under drought at different levels of water stress, as it is a common clone used to be grown in Uttarakhand for making paper and plywood. The cuttings of Populus deltoides L. (clone Kranti) were exposed to four different watering regimes (100, 75, 50 and 25% of the field capacity) and changes in physiological and biochemical parameters related with drought tolerance were recorded. Alterations in physiological (i.e. decrease in relative water content) and biochemical parameters (i.e. increase in proline and soluble sugar content and build-up of malondialdehyde by-products) occurred in all the three levels of water stress, although drought represented the major determinant. Drought treatments (75%, 50% and 25% FC) decreased plant height, radial stem diameter, harvest index, total biomass content and RWC in all the three watering regimes compared to control (100% FC). Biochemical parameters like proline, soluble sugar and MDA content increased with severity and duration of stress, which helped plants to survive under severe stress. It was analyzed that for better wood yield poplar seedlings should avail either optimum amount of water (amount nearly equal to field capacity of soil) or maximum withdrawal up to 75% of field capacity up to seedling establishment period (60 days). Furthermore, this study manifested that acclimation to drought stress is related with the rapidity, severity, and duration of the drought event of the poplar species.


2020 ◽  
Vol 13 (1) ◽  
pp. 14
Author(s):  
Annamaria Castrignanò ◽  
Antonella Belmonte ◽  
Ilaria Antelmi ◽  
Ruggiero Quarto ◽  
Francesco Quarto ◽  
...  

Xylella fastidiosa subsp. pauca (Xfp) is one of the most dangerous plant pathogens in the world. Identified in 2013 in olive trees in south–eastern Italy, it is spreading to the Mediterranean countries. The bacterium is transmitted by insects that feed on sap, and causes rapid wilting in olive trees. The paper explores the use of Unmanned Aerial Vehicle (UAV) in combination with a multispectral radiometer for early detection of infection. The study was carried out in three olive groves in the Apulia region (Italy) and involved four drone flights from 2017 to 2019. To classify Xfp severity level in olive trees at an early stage, a combined method of geostatistics and discriminant analysis was implemented. The results of cross-validation for the non-parametric classification method were of overall accuracy = 0.69, mean error rate = 0.31, and for the early detection class of accuracy 0.77 and misclassification probability 0.23. The results are promising and encourage the application of UAV technology for the early detection of Xfp infection.


2021 ◽  
Vol 13 (5) ◽  
pp. 2923
Author(s):  
Botir Khaitov ◽  
Munisa Urmonova ◽  
Aziz Karimov ◽  
Botirjon Sulaymonov ◽  
Kholik Allanov ◽  
...  

Water deficiency restricts plant productivity, while excessive soil moisture may also have an adverse impact. In light of this background, field trials were conducted in secondary saline soil (EC 6.5 dS m−1) at the experimental station of Tashkent State Agrarian University (TSAU), Uzbekistan to determine drought tolerance of licorice (Glycyrrhiza glabra) by exposure to four levels of water deficit, namely control (70–80%), moderate (50–60%), strong (30–40%) and intense (10–20%) relative water content (WC) in the soil. The moderate drought stress exhibited positive effects on the morphological and physiological parameters of licorice, and was considered to be the most suitable water regime for licorice cultivation. Plant growth under the 50–60% WC treatment was slightly higher as compared to 70–80% WC treatment, exhibiting weak water deficit promotes licorice growth, root yield and secondary metabolite production. In particular, secondary metabolites i.e., ash, glycyrrhizic acid, extractive compounds and flavonoids, tended to increase under moderate water deficit, however further drought intensification brought a sharp decline of these values. These results contribute to the development of licorice cultivation technologies in arid regions and the most important consideration is the restoration of ecological and economical functions of the dryland agricultural system.


Author(s):  
Sabrina Di Masi ◽  
Giuseppe E. De Benedetto ◽  
Cosimino Malitesta ◽  
Maria Saponari ◽  
Cinzia Citti ◽  
...  

AbstractOlive quick decline syndrome (OQDS) is a disorder associated with bacterial infections caused by Xylella fastidiosa subsp. pauca ST53 in olive trees. Metabolic profile changes occurring in infected olive trees are still poorly investigated, but have the potential to unravel reliable biomarkers to be exploited for early diagnosis of infections. In this study, an untargeted metabolomic method using high-performance liquid chromatography coupled to quadrupole-time-of-flight high-resolution mass spectrometry (HPLC-ESI-Q-TOF-MS) was used to detect differences in samples (leaves) from healthy (Ctrl) and infected (Xf) olive trees. Both unsupervised and supervised data analysis clearly differentiated the groups. Different metabolites have been identified as potential specific biomarkers, and their characterization strongly suggests that metabolism of flavonoids and long-chain fatty acids is perturbed in Xf samples. In particular, a decrease in the defence capabilities of the host after Xf infection is proposed because of a significant dysregulation of some metabolites belonging to flavonoid family. Moreover, oleic acid is confirmed as a putative diffusible signal factor (DSF). This study provides new insights into the host-pathogen interactions and confirms LC-HRMS-based metabolomics as a powerful approach for disease-associated biomarkers discovery in plants. Graphical abstract


2021 ◽  
Vol 185 ◽  
pp. 112695
Author(s):  
Maria Celeste Dias ◽  
Diana C.G.A. Pinto ◽  
Catarina Figueiredo ◽  
Conceição Santos ◽  
Artur M.S. Silva

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