Analysis of olive grove destruction by xylella fastidiosa bacterium on the land surface temperature in Salento detected using satellite images

Agricultural activity replaces natural vegetation with cultivated land and it is a major cause of local and global climate change. Highly specialized agricultural production leads to extensive monoculture farming with a low biodiversity that may cause low landscape resilience. This is the case on the Salento peninsula, in the Apulia Region of Italy, where the Xylella fastidiosa bacterium has caused the mass destruction of olive trees, many of them in monumental groves. The historical land cover that characterized the landscape is currently in a transition phase and can strongly affect climate conditions. This study aims to analyze how the destruction of olive groves by X. fastidiosa affects local climate change. Land surface temperature (LST) data detected by Landsat 8 and MODIS satellites are used as a proxies for microclimate mitigation ecosystem services linked to the evolution of the land cover. Moreover, recurrence quantification analysis was applied to the study of LST evolution. The results showed that olive groves are the least capable forest type for mitigating LST, but they are more capable than farmland, above all in the summer when the air temperature is the highest. The differences in the average LST from 2014 to 2020 between olive groves and farmland ranges from 2.8 °C to 0.8 °C. Furthermore, the recurrence analysis showed that X. fastidiosa was rapidly changing the LST of the olive groves into values to those of farmland, with a difference in LST reduced to less than a third from the time when the bacterium was identified in Apulia six years ago. The change generated by X. fastidiosa started in 2009 and showed more or less constant behavior after 2010 without substantial variation; therefore, this can serve as the index of a static situation, which can indicate non-recovery or non-transformation of the dying olive groves. Failure to restore the initial environmental conditions can be connected with the slow progress of the uprooting and replacing infected plants, probably due to attempts to save the historic aspect of the landscape by looking for solutions that avoid uprooting the diseased plants. This suggests that social-ecological systems have to be more responsive to phytosanitary epidemics and adapt to ecological processes, which cannot always be easily controlled, to produce more resilient landscapes and avoid unwanted transformations

Antioxidant Compounds of Potato Breeding Genotypes and Commercial Cultivars with Yellow, Light Yellow, and White Flesh in Iran

Potatoes are a staple food with high antioxidant properties that can positively affect population health. The beneficial effects of potatoes have been attributed to tuber quality. However, the tuber quality related researches at genetic levels are very few. Sexual hybridization is a powerful strategy for producing new and valuable genotypes with high quality. In this study, 42 breeding potato genotypes in Iran were selected based on appearance characteristics such as shape, size, color, eyes of tubers, and tuber yield and marketability. The tubers were evaluated for their nutritional value and properties, viz. phenolic content, flavonoids, carotenoids, vitamins, sugars, proteins, and antioxidant activity. Potato tubers with white flesh and colored skin had significantly higher levels of ascorbic acid and total sugar. The result showed that higher phenolic, flavonoid, carotenoid, protein concentration, and antioxidant activity were noted in yellow-fleshed. Burren (yellow-fleshed) tubers had more antioxidant capacity in comparison to genotypes and cultivars, which did not differ significantly with genotypes 58, 68, 67 (light yellow), 26, 22, and 12 (white). The highest correlation coefficients in antioxidant compounds were related to total phenol content and FRAP, suggesting that phenolics might be crucial predictors of antioxidant activities. The concentration of antioxidant compounds in the breeding genotypes was higher than in some commercial cultivars, and higher antioxidant compounds content and activity were detected in yellow-fleshed cultivars. Based on current results, understanding the relationship between antioxidant compounds and the antioxidant activity of potatoes could be very helpful in potato breeding projects

Xylella fastidiosa subsp. pauca (CoDiRO strain) infection in four olive (Olea europaea L.) cultivars: profile of phenolic compounds in leaves and progression of leaf scorch symptoms

Xylella fastidiosa subsp. pauca (Xfp), strain CoDiRO, infects a broad range of olive (Olea europaea L.) cultivars. The profile of phenolic compounds, progression of leaf scorch symptoms and population density of X. fastidiosa were analyzed in response to Xfp infection, in four olive cultivars (Cellina di Nardò, Ogliarola di Lecce, Frantoio and Leccino). Differences in X. fastidiosa multiplication in xylem tissues were estimated using qPCR assays, showing that cvs. Cellina di Nardò and Ogliarola di Lecce were characterized by fewer threshold cycles than for cvs. Frantoio and Leccino. Periodical visual inspections of symptomatic plants estimated disease severity and progression using a disease rating scale; cvs. Frantoio and Leccino showed some disease resistance with up to 3-fold severity scores than those for cvs. Cellina di Nardò and Ogliarola. During vegetative growth, Xfp-positive leaf samples were analyzed using HPLC-ESI–TOF–MS. Among quantified phenolic compounds, Xfp infection modified hydroxytyrosol glucoside and quinic acid. Constitutive levels of hydroxytyrosol glucoside were greater in cvs. Frantoio and Leccino compared to Cellina di Nardò and Ogliarola di Lecce, while levels were strongly reduced in infected plants (95% reduction in Cellina di Nardò, 94% in Ogliarola di Lecce, 97% in Frantoio and 98% in, Leccino). Constitutive levels of quinic acid did not differ among cultivars, but strongly increased in infected Cellina di Nardò and Ogliarola di Lecce (5-fold increases), and to a lesser extent (4-fold increases) in infected Frantoio and Leccino. These results were consistent with the previously reported positive association of quinic acid with X. fastidiosa subsp. fastidiosa symptoms and titres in grapevine. Differences in the induced responses of these phenolic compounds among cultivars suggest that they play defensive roles in olive tree response to X. fastidiosa infection

Metabarcoding libraries (fungi; 5.8S-Fun, ITS4-Fun primers) from olive tree leaf samples

Fungal pair-end metabarcoding libraries from the paper "Resistance against invasion: the role of the endophytic community against Xylella fastidiosa in olive tree". Classification (Ctrl = controls): SX25     FLD0097.FS3105PR01_fungi SX25 Ctrl     FLD0105.FS3105PR01Ctrl_fungi SX27     FLD0113.AM2507SN02_fungi SX27 Ctrl     FLD0121.AM2507SN02Ctrl_fungi SX29     FLD0129.AM2507SN03_fungi SX29 Ctrl     FLD0137.AM2507SN03Ctrl_fungi SX30     FLD0145.FS1709PA02_fungi SX30 Ctrl     FLD0153.FS1709PA02Ctrl_fungi SX31     FLD0161.FS2407ML01_fungi SX31 Ctrl     FLD0169.FS2407ML01Ctrl_fungi SX32     FLD0177.LP2011ML01_fungi SX32 Ctrl     FLD0185.LP2011ML01Ctrl_fungi SX61     FLD0098.FG1505SP02_fungi SX61 Ctrl     FLD0106.FG1505SP02Ctrl_fungi SX63     FLD0114.FG1905UG01_fungi SX63 Ctrl     FLD0122.FG1905UG01Ctrl_fungi SX65     FLD0130.FG1905SP01_fungi SX65 Ctrl     FLD0138.FG1905SP01Ctrl_fungi SX67     FLD0146.FG10502BA01_fungi SX67 Ctrl     FLD0154.FG1502BA01Ctrl_fungi SX69     FLD0162.FG1905RU01_fungi SX69 Ctrl     FLD0170.FG1905RU01Ctrl_fungi SX71     FLD0178.FG1001BA02_fungi SX71 Ctrl     FLD0186.FG1001BA02Ctrl_fungi SX73     FLD0099.GL0103CO09_fungi SX73 Ctrl     FLD0107.GL0103CO09Ctrl_fungi SX75     FLD0115.GL0705CO13_fungi SX75 Ctrl     FLD0123.GL0705CO13Ctrl_fungi SX77     FLD0131.GL08050C16_fungi SX77 Ctrl     FLD0139.GL08050C16Ctrl_fungi SX79     FLD0147.GL08050C17_fungi SX79 Ctrl     FLD0155.GL08050C17Ctrl_fungi SX81     FLD0163.GL1912LV14_fungi SX81 Ctrl     FLD0171.GL1912LV14Ctrl_fungi SX83     FLD0179.GL1705LV20_fungi SX83 Ctrl     FLD0187.GL1705LV20Ctrl_fungi SX85     FLD0100.GL2902LQ01_fungi SX85 Ctrl     FLD0108.GL2902LQ01Ctrl_fungi SX87     FLD0116.GL0705CO10_fungi SX87 Ctrl     FLD0124.GLO705CO10Ctrl_fungi SX89     FLD0132.LP1606GA01_fungi SX89 Ctrl     FLD0140.LP1606GA01Ctrl_fung

Metabarcoding libraries (bacteria; CS1, CS2 primers) from olive tree leaf samples

Bacterial pair-end metabarcoding libraries from the paper "Resistance against invasion: the role of the endophytic community against Xylella fastidiosa in olive tree". Classification (Ctrl = controls): SX25    FLD0097.FS3105PR01 SX25 Ctrl    FLD0105.FS3105PR01Ctrl SX27    FLD0113.AM2507SN02 SX27 Ctrl    FLD0121.AM2507SN02Ctrl SX29    FLD0129.AM2507SN03 SX29 Ctrl    FLD0137.AM2507SN03Ctrl SX30    FLD0145.FS1709PA02 SX30 Ctrl    FLD0153.FS1709PA02Ctrl SX31    FLD0161.FS2407ML01 SX31 Ctrl    FLD0169.FS2407ML01Ctrl SX32    FLD0177.LP2011ML01 SX32 Ctrl    FLD0185.LP2011ML01Ctrl SX61    FLD0098.FG1505SP02 SX61 Ctrl    FLD0106.FG1505SP02Ctrl SX63    FLD0114.FG1905UG01 SX63 Ctrl    FLD0122.FG1905UG01Ctrl SX65    FLD0130.FG1905SP01 SX65 Ctrl    FLD0138.FG1905SP01Ctrl SX67    FLD0146.FG10502BA01 SX67 Ctrl    FLD0154.FG1502BA01Ctrl SX69    FLD0162.FG1905RU01 SX69 Ctrl    FLD0170.FG1905RU01Ctrl SX71    FLD0178.FG1001BA02 SX71 Ctrl    FLD0186.FG1001BA02Ctrl SX73    FLD0099.GL0103CO09 SX73 Ctrl    FLD0107.GL0103CO09Ctrl SX75    FLD0115.GL0705CO13 SX75 Ctrl    FLD0123.GL0705CO13Ctrl SX77    FLD0131.GL08050C16 SX77 Ctrl    FLD0139.GL08050C16Ctrl SX79    FLD0147.GL08050C17 SX79 Ctrl    FLD0155.GL08050C17Ctrl SX81    FLD0163.GL1912LV14 SX81 Ctrl    FLD0171.GL1912LV14Ctrl SX83    FLD0179.GL1705LV20 SX83 Ctrl    FLD0187.GL1705LV20Ctrl SX85    FLD0100.GL2902LQ01 SX85 Ctrl    FLD0108.GL2902LQ01Ctrl SX87    FLD0116.GL0705CO10 SX87 Ctrl    FLD0124.GLO705CO10Ctrl SX89    FLD0132.LP1606GA01 SX89 Ctrl    FLD0140.LP1606GA01Ctr

16S libraries of endophytic communities in olive trees subjected to salt stress

Paired-end sequences spanning the V3–V4 regions of the bacterial 16S rRNA. Bacterial metabarcoding of Olive tree samples subjected to salt stress. 4 cultivars (Frantoio, Leccino, Lecciana, and Oliana), three experimental conditions (Control, 100 mM and 200 mM of sodium chloride) and two-time points (T0, at the beginning of the experiment; T1, at the end of the experiment) were used.  Metabarcoding data were then coupled with pigment and proline analyses to better describe the olive tree response to salinity stress. Lecciana; "Lc" Leccino; "Lcc" Oliana; "Og" Frantoio; "Fr" The library acronym includes the cultivar (e. g., Lc), the time point (e. g., t1), the treatment (e. g., 200), and the replicate (e.g., 3)

Secondary Metabolites in Xylella fastidiosa–Plant Interaction

During their evolutionary history, plants have evolved the ability to synthesize and accumulate small molecules known as secondary metabolites. These compounds are not essential in the primary cell functions but play a significant role in the plants’ adaptation to environmental changes and in overcoming stress. Their high concentrations may contribute to the resistance of the plants to the bacterium Xylella fastidiosa, which has recently re-emerged as a plant pathogen of global importance. Although it is established in several areas globally and is considered one of the most dangerous plant pathogens, no cure has been developed due to the lack of effective bactericides and the difficulties in accessing the xylem vessels where the pathogen grows and produces cell aggregates and biofilm. This review highlights the role of secondary metabolites in the defense of the main economic hosts of X. fastidiosa and identifies how knowledge about biosynthetic pathways could improve our understanding of disease resistance. In addition, current developments in non-invasive techniques and strategies of combining molecular and physiological techniques are examined, in an attempt to identify new metabolic engineering options for plant defense

Xylem Embolism and Pathogens: Can the Vessel Anatomy of Woody Plants Contribute to <i>X. fastidiosa</i> Resistance?

The maintenance of an intact water column in the xylem lumen several meters above the ground is essential for woody plant viability. In fact, abiotic and biotic factors can lead to the formation of emboli in the xylem, interrupting sap flow and causing consequences on the health status of the plant. Anyway, the tendency of plants to develop emboli depends on the intrinsic features of the xylem, while the cyto-histological structure of the xylem plays a role in resistance to vascular pathogens, as in the case of the pathogenic bacterium Xylella fastidiosa. Analysis of the scientific literature suggests that on grapevine and olive, some xylem features can determine plant tolerance to vascular pathogens. However, the same trend was not reported in citrus, indicating that X. fastidiosa interactions with host plants differ by species. Unfortunately, studies in this area are still limited, with few explaining inter-cultivar insights. Thus, in a global context seriously threatened by X. fastidiosa, a deeper understanding of the relationship between the physical and mechanical characteristics of the xylem and resistance to stresses can be useful for selecting cultivars that may be more resistant to environmental changes, such as drought and vascular pathogens, as a way to preserve agricultural productions and ecosystems

A Physiological and Molecular Focus on the Resistance of “Filippo Ceo” Almond Tree to <i>Xylella fastidiosa</i>

The impact of Xylella fastidiosa (Xf) subsp. pauca on the environment and economy of Southern Italy has been devastating. To restore the landscape and support the local economy, introducing new crops is crucial for restoring destroyed olive groves, and the almond tree (Prunus dulcis Mill. D. A. Webb) could be a promising candidate. This work focused on the resistance of the cultivar “Filippo Ceo” to Xf and evaluated its physiological and molecular responses to individual stresses (drought or pathogen stress) and combined stress factors under field conditions over three seasons. Filippo Ceo showed a low pathogen concentration (≈103 CFU mL−1) and a lack of almond leaf scorch symptoms. Physiologically, an excellent plant water status was observed (RWC 82–89%) regardless of the stress conditions, which was associated with an increased proline content compared to that of the control plants, particularly in response to Xf stress (≈8-fold). The plant’s response did not lead to a gene modulation that was specific to different stress factors but seemed more indistinct: upregulation of the LEA and DHN gene transcripts by Xf was observed, while the PR transcript was upregulated by drought stress. In addition, the genes encoding the transcription factors (TFs) were differentially induced by stress conditions. Filippo Ceo could be an excellent cultivar for coexistence with Xf subps. pauca, confirming its resistance to both water stress and the pathogen, although this similar health status was achieved differently due to transcriptional reprogramming that results in the modulation of genes directly or indirectly involved in defence strategies