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Background: Beneficial bacteria-plant interactions play an important role in agriculture, positively affecting plant status and improving product quality. Bacterial endophytes contribute to host plant protection and survival. Aim: This study characterised the bacterial communities present in soil, leaf surface and xylem sap of olive trees, and investigated their response under a sustainable (Smng) or a conventional (Cmng) management system in an olive grove located in southern Italy. The aims are: (a) to understand if soil bacteria enter xylem and reach leaves and (b) to verify if the bacterial communities in the two management systems deeply differ due to the different agronomic practices applied in Smng and in Cmng. Methods: Therefore, a metagenomic approach was used to detect microorganisms, in order to estimate bacterial diversity and abundance, and to identify the bacterial taxa in the three analysed compartments in plants subjected to Smng and Cmng systems. Results: Bacterial communities came from the soil and reached aerial plant parts through xylem sap. The application of different agronomic practices influenced the composition of soil bacterial communities. Conclusions: The potential benefits of the specific bacterial taxa detected under the Smng system could improve plant growth protection and provide a higher crop quality in fruit plants. [ABSTRACT FROM AUTHOR]

Higher calcium (Ca) concentration in several fleshy fruit including kiwifruit is a pre-requisite for lower incidence of Ca-related diseases and improved fruit nutritional value. This review examines the internal and external factors operating along the soil-to-fruit pathway that are involved in the uptake and partitioning of Ca in kiwifruit vines. After a brief description of fruit growth and the dynamic of nutrient accumulation during fruit development, the review considers the role of soil Ca concentration and availability, root elongation, mass flow in the apoplast, fruit transpiration, competition between fruit and highly transpiring leaves, weather variables and soil moisture. How fruit morphological and anatomical traits, including skin anatomy, xylem development and hydraulic resistance, influence physiological processes such as transpiration and impact on Ca accumulation is also discussed. The review highlights that approximately 80% of the total Ca content of fruit is accumulated during the early weeks after fruit-set, suggesting that failure of good fruit Ca nutrition at that time may lead to poor fruit Ca content at harvest. Therefore, based on the analysis of the internal and external factors that influence Ca accumulation, recommendations are made for orchard practices that maximize Ca accumulation in the kiwifruit berry, including optimal pollination, nutrient and irrigation management, and manipulation of canopy architecture. [ABSTRACT FROM AUTHOR]

Abstract: A field trial was conducted over a seven-year period, in Mediterranean peach orchard. The aims were (i) to explore the effects of alternative soil-management practices (A mng) on soil and litter carbon (C) reserves, (ii) to monitor the seasonal and (iii) spatial variations of soil CO2 flushes. The alternative management included no tillage, retention of all aboveground biomass and application of imported organic amendments (15tha−1 y−1 fresh weigh). Locally conventional management (L mng) served as the control: i.e. tillage, mineral fertilisation, removal of prunings. The mean total annual C inputs were 4.2 and 2.4tha−1 in A mng and L mng, respectively. Spatial and temporal variations in CO2 soil emissions over a 20m2 plot (×2) were assessed (Li-6400, LI-COR, USA) on the assumption that root topography and microbial activity declined systematically with distance from the row line. Under A mng practices soil C significantly increased up to 1.78% against 1.38% at L mng block. The C stored as litter and dead wood in A mng, was 16-times that in L mng. On a whole-season basis, CO2 losses were 20% higher in A mng than in L mng. Soil CO2 emissions were mostly from the in-row, with the inter-row emissions being lower, especially due to reduced soil-water content during the drier months. It is concluded that despite a higher CO2 soil emissions, alternative management techniques will partially offset atmospheric CO2 rise through increased soil C reserves, and that spatial variability of emissions must be taken into account if the accuracy of estimates of large-scale emissions are to be improved. [Copyright &y& Elsevier]

In conventional olive growing, frequent soil tillage strongly reduces the complexity and diversity of the agro-ecosystem. Here, a metabolomic analysis was carried out on the xylem sap (XS) of olive plants (Olea europaea L.) from a grove located in Southern Italy (Basilicata region). The orchard has been divided in two plots that have been managed for 18 years with two different systems: a) 'sustainable management' (S mng), with no-tillage, fertigation and internal C-inputs (spontaneous weeds and pruning residues), and b) an adjacent rainfed 'conventional management' (C mng), that included soil tillage and mineral fertilization. The XS was extracted from olive shoots in two sampling times (ST1: May; ST2: October) using a Sholander pressure chamber, and its metabolome analyzed by ultra-high performance liquid chromatography (UHPLC) coupled to a hybrid quadrupole-time-of-flight mass spectrometer (QTOF-MS). The discriminating compounds were 94 at ST1 and 119 at ST2, and 35 of them were in common between the two sampling times. The majority of the discriminating metabolites (73 on 94 at ST1, and 109 on 119 at ST2) were found at higher concentration in the XS of S mng plants, compared to that of C mng ones. Most of the discriminating metabolites found in XS (about 80%, both at ST1 and ST2) were involved in plant secondary metabolism, mainly for plant chemical defense, growth regulation and signal transduction. The most prevailing class of compounds included terpenoids, phytohormones, alkaloids, sterols/steroids, retinols/retinoids, tocopherols and carotenoids. For the first time, we have demonstrated that the XS of a tree crop significantly responds to a shift of soil management. Generally, the plants of the S mng plot showed an up-regulated secondary metabolism. The results of our study encourage the use of a set of sustainable agricultural practices in a productive orchard, in order to enhance plant physiological status, increase yield quantity/quality, safeguard the environment and ameliorate human health. • Olive plants were managed by a sustainable (S mng) or a conventional (C mng) system. • A metabolomic analysis (UHPLC/QTOF-MS) of extracted xylem sap was conducted. • Deep differences in xylem sap composition were observed between S mng and C mng. • The plants from the S mng showed an up-regulated secondary metabolism. • The xylem sap of olive trees responded to a shift of soil management. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • A sustainable (S mng) and a conventional (C mng) olive orchard were compared. • Pedological, chemical, and microbiological analyses on soils were carried out. • S mng showed a higher soil C and N in the topsoil layers, and lower pH. • N-cycling bacteria were higher in S mng but bacterial diversity did not change. • A new sustainable approach for optimizing soil C and N cycling is proposed. Abstract Under Mediterranean type climates, a sustainable soil management aimed at increasing soil organic carbon and microbiological diversity is of key importance. The aim of this study was to characterize and compare soils from a mature Mediterranean olive (Olea europaea L.) orchard subjected to two different soil management systems (sustainable, S mng , and conventional, C mng) for 18 years. Composite soil samples were analyzed qualitatively (pedological determinations) and quantitatively (soil C, N and pH). Bacterial metabolic activity and diversity were evaluated spectrophometrically by the Biolog® assay, while 16S-based metagenomics analysis was used to analyse the abundance of N-cycling bacteria. From the general analysis of the data obtained by the study of soil profiles and litter, C and N dynamics, and the genetic and functional diversity of soil bacteria, it emerged that the S mng system caused an improvement in soil organic matter in the topsoil layers, compared to the C mng system, with consequent increases in the abundance of soil N-cycling bacteria but without affecting the indices related to total bacterial metabolic activity and diversity. The results obtained could promote the development of new approaches for optimizing soil carbon cycling, managing nutrient transport, and sustaining and improving olive yield and quality. [ABSTRACT FROM AUTHOR]