The Agricultural Revolution and plant domestication in the Near East (among its components) have fascinated generations of scholars. Here, we narrate the history of ideas underlying plant domestication research since the late 19th century. Biological and cultural perspectives are presented through two prevailing models: one views plant domestication as a protracted, unconscious evolutionary mutualistic (noncentric) process. The second advocates a punctuated, knowledge-based human initiative (centric). We scrutinize the research landscape while assessing the underlying evolutionary and cultural mechanisms. A parsimony measure indicates that the punctuated-centric view better accords with archaeological records, and the geobotany and biology of the species, and requires fewer assumptions. The protracted alternative requires many assumptions, does not account for legume biology, fails to distinguish domestication from postdomestication changes, and, therefore, is less parsimonious.

Most plants invest the greater part of their effort in tissues and organs (sinks) that are important for their long-term survival. Fruits and seeds represent such organs and they are considered as permanent, irreversible sinks. In contrast to temporary sinks, the plant cannot retrieve the invested storage materials from fruits and seeds because they abscise from the mother plant. Developing fruits and seeds are usually strong sinks, exhibiting a very high amount of assimilate import. The amount of storage material that the plants invest in seeds is huge. Thus it is not surprising that approximately 70% of all food for human consumption comes from seeds, mostly cereals (“endospermic seeds”) and legumes (“nonendospermic seeds”) (Bewley and Black, 1985). © 1995 by Marcel Dekker. All rights reserved.

Much of the plant material we eat originates from reproductive and storage sinks. Crop yield is the ultimate product of the whole plant’s net photosynthesis and the relative partitioning of dry matter to the organ of agricultural significance. The photosynthetic activity of the sources determines the potential amount of assimilates that can be transported to the sinks. The question is whether assimilate distribution to the sinks is controlled by the source (a feed-forward effect) or by the sink (a feedback effect). Many investigators have suggested that the overall physiological and metabolical processes taking place in the sink tissues are the main factors determining assimilate partitioning (see Krapp et al. 1993). However, a recent discussion of the question of sink strength and the extent of its importance in source-sink relationships (Farrar 1993) emphasized the range of contradictory views. © 1996 by Marcel Dekker, Inc. All Rights Reserved.

Adopting an interdisciplinary approach to the study of photoassimilate partitioning and source-sink relationhips, this work details the major aspects of source-sink physiology and metabolism, the integration of individual components and photoassimilate partitioning, and the whole plant source-sink relationships in 16 agriculturally important crops. The work examines in detail the components of carbon partitioning, such as ecology, photosynthesis, loading, transport and anatomy, and discusses the impact of genetic, environmental and agrotechnical factors on the parts of whole plant source-link physiology. © 1996 by Marcel Dekker, Inc. All Rights Reserved.

Most plants invest the greater part of their effort in tissues and organs (sinks) that are important for their long-term survival. Fruits and seeds represent such organs and they are considered as permanent, irreversible sinks. In contrast to temporary sinks, the plant cannot retrieve the invested storage materials from fruits and seeds because they abscise from the mother plant. Developing fruits and seeds are usually strong sinks, exhibiting a very high amount of assimilate import. The amount of storage material that the plants invest in seeds is huge. Thus it is not surprising that approximately 70% of all food for human consumption comes from seeds, mostly cereals (“endospermic seeds”) and legumes (“nonendospermic seeds”) (Bewley and Black, 1985). © 1995 by Marcel Dekker. All rights reserved.

Selection for inflorescence architecture with improved flower production and yield is common to many domesticated crops. However, tomato inflorescences resemble wild ancestors, and breeders avoided excessive branching because of low fertility. We found branched variants carry mutations in two related transcription factors that were selected independently. One founder mutation enlarged the leaf-like organs on fruits and was selected as fruit size increased during domestication. The other mutation eliminated the flower abscission zone, providing “jointless” fruit stems that reduced fruit dropping and facilitated mechanical harvesting. Stacking both beneficial traits caused undesirable branching and sterility due to epistasis, which breeders overcame with suppressors. However, this suppression restricted the opportunity for productivity gains from weak branching. Exploiting natural and engineered alleles for multiple family members, we achieved a continuum of inflorescence complexity that allowed breeding of higher-yielding hybrids. Characterizing and neutralizing similar cases of negative epistasis could improve productivity in many agricultural organisms. Video Abstract © 2017 Elsevier Inc.

To explore the genetic robustness (canalization) of metabolism, we examined the levels of fruit metabolites in multiple harvests of a tomato introgression line (IL) population. The IL partitions the whole genome of the wild species Solanum pennellii in the background of the cultivated tomato (Solanum lycopersicum). We identified several metabolite quantitative trait loci that reduce variability for both primary and secondary metabolites, which we named canalization metabolite quantitative trait loci (cmQTL). We validated nine cmQTL using an independent population of backcross inbred lines, derived from the same parents, which allows increased resolution in mapping the QTL previously identified in the ILs. These cmQTL showed little overlap with QTL for the metabolite levels themselves. Moreover, the intervals they mapped to harbored few metabolism-associated genes, suggesting that the canalization of metabolism is largely controlled by regulatory genes. © American Society of Plant Biologists.

Modern commercial tomato varieties are substantially less flavorful than heirloom varieties. To understand and ultimately correct this deficiency, we quantified flavor-associated chemicals in 398 modern, heirloom, and wild accessions. A subset of these accessions was evaluated in consumer panels, identifying the chemicals that made the most important contributions to flavor and consumer liking. We found that modern commercial varieties contain significantly lower amounts of many of these important flavor chemicals than older varieties. Whole-genome sequencing and a genome-wide association study permitted identification of genetic loci that affect most of the target flavor chemicals, including sugars, acids, and volatiles. Together, these results provide an understanding of the flavor deficiencies in modern commercial varieties and the information necessary for the recovery of good flavor through molecular breeding. Copyright © 2017, American Association for the Advancement of Science.

Updates in nanopore technology have made it possible to obtain gigabases of sequence data. Prior to this, nanopore sequencing technology was mainly used to analyze microbial samples. Here, we describe the generation of a comprehensive nanopore sequencing data set with a median read length of 11,979 bp for a self-compatible accession of the wild tomato species Solanum pennellii. We describe the assembly of its genome to a contig N50 of 2.5 MB. The assembly pipeline comprised initial read correction with Canu and assembly with SMARTdenovo. The resulting raw nanopore-based de novo genome is structurally highly similar to that of the reference S. pennellii LA716 accession but has a high error rate and was rich in homopolymer deletions. After polishing the assembly with Illumina reads, we obtained an error rate of <0.02% when assessed versus the same Illumina data. We obtained a gene completeness of 96.53%, slightly surpassing that of the reference S. pennellii. Taken together, our data indicate that such long read sequencing data can be used to affordably sequence and assemble gigabase-sized plant genomes. © 2017 The author(s).

Stomatal oscillations are cyclic opening and closing of stomata, presumed to initiate from hydraulic mismatch between leaf water supply and transpiration rate. To test this assumption, mismatches between water supply and transpiration were induced using manipulations of vapour pressure deficit (VPD) and light spectrum in banana (Musa acuminata). Simultaneous measurements of gas exchange with changes in leaf turgor pressure were used to describe the hydraulic mismatches. An increase of VPD above a certain threshold caused stomatal oscillations with variable amplitudes. Oscillations in leaf turgor pressure were synchronized with stomatal oscillations and balanced only when transpiration equaled water supply. Surprisingly, changing the light spectrum from red and blue to red alone at constant VPD also induced stomatal oscillations – while the addition of blue (10%) to red light only ended oscillations. Blue light is known to induce stomatal opening and thus should increase the hydraulic mismatch, reduce the VPD threshold for oscillations and increase the oscillation amplitude. Unexpectedly, blue light reduced oscillation amplitude, increased VPD threshold and reduced turgor pressure loss. These results suggest that additionally, to the known effect of blue light on the hydroactive opening response of stomata, it can also effect stomatal movement by increased xylem–epidermis water supply. © 2017 John Wiley & Sons Ltd

Key message: Narrow stem size in limitingVitisrootstocks imposes a morphological constraint on the scion via reduced annual ring size, and thus reduces hydraulic conductivity and subsequently physiological performance and yield. Abstract: Graft is a union between two separate species or cultivars, which produces a chimera plant with new qualities—as rootstock affects scion growth, yield, and adaptability to different environmental conditions. In Vitis, it is possible to generate rootstock/scion combinations that produce a desired drought stress effect crucial for high-quality wine production, though the mechanisms for such interactions are complex and poorly understood. The current study was done on vines with an identical scion (Vitis vinifera ‘Cabernet Sauvignon’) grafted on three different rootstocks—either Riparia Gloire, Paulsen 1103 or 420A—in attempt to explain the differences in water status by examining the underlying anatomical constraints and calculated theoretical hydraulic conductivity. There was a significant difference in physiological responses and yield between the grafts. Riparia Gloire grafts had the lowest water potentials and the highest quality grapes, together with low root, scion stem, and branch theoretical hydraulic conductivity. In scions grafted on Riparia Gloire, the annual growth rings were significantly narrower than in the other two grafts, causing a significantly lower theoretical hydraulic conductivity per annual ring. The narrow annual ring size in scion stem was imposed by the morphological constraint of the stem size. In hydraulically inferior Riparia Gloire grafts, the difference was disproportionally large, with a wide scion grafted on a very narrow rootstock, and Paulsen 1103 had the smoothest graft union. Our results indicate that the ability to develop stronger drought stress in Vitis grafts depends on rootstock-imposed morphological restriction of hydraulic conductivity. © 2016, Springer-Verlag Berlin Heidelberg.

Treated wastewater (TWW) is a major source of water for agriculture in Israel; however, recent reports indicate a marked yield loss in TWW-irrigated avocado and citrus orchards planted in clayey soils. The association of the yield loss with clayey soils rather than sandy soils suggests that it is associated with conditions in the root zone, and specifically poor aeration. A three-year study (2012-2015) was conducted in an avocado orchard planted in clayey soil, comparing the oxygen and redox conditions in the root zone of TWW-irrigated plots with fresh water (FW)-irrigated plots, together with the physiological status of the trees. Soil parameters included: continuous in-situ measurement of soil-water tension (SWT), soil oxygen, and soil redox potential, and periodic measurements of soil solution composition. Physiological parameters included: mineral composition of plant tissue from the leaves, trunk xylem and roots, root growth, yield, fruit setting, plant volume, and yield. TWW-irrigated plots were found to endure longer periods of low SWT indicating higher water content, accompanied by lower oxygen levels and more reduced conditions in comparison to FW-irrigated plots. The differences in these soil parameters between treatments were greater during the irrigation season than during the rainy period. The more reduced conditions in the TWW plots did not lead to significant differences in Fe or Mn concentrations in the soil solution or in plant leaves. TWW soil solution had significantly higher Na levels compared with FW. This did not affect the leaf Na content, but was expressed in substantially higher Na content in the root and trunk xylem, with up to seven times more trunk xylem Na in TWW-irrigated plants compared with FW-irrigated plants. Root growth was significantly hindered in TWW-irrigated plots compared with FW-irrigated plots. A negative correlation was found between root growth and the duration of hypoxic conditions, and similarly between root growth and the Na levels in the roots. TWW-irrigated plants had greater fruitlet numbers at the initial fruit-setting stage, but had a smaller number of fruit and a lower yield at harvest. The yield (kg/tree) negatively correlated with the duration of hypoxic conditions in the root zone but not with the Na levels in the roots or xylem. Our findings point towards a substantial role of oxygen deprivation as a major factor leading to the damage to TWW-irrigated orchards in clayey soils. Based on the assimilation of data, we suggest that a downward cascade is instigated in the TWW-irrigated orchards by increased input of Na into the soil, leading to degradation of soil hydraulic properties and reduced aeration. Impaired physiological functioning of the roots due to limited oxygen supply results in less roots growth, lower water uptake and impaired selectivity against Na uptake, thus imposing a negative feedback to increase soil water content, reduce aeration and root-zone oxygen availability for the roots, and further impair plant resistance to the high Na levels. © 2017 by Koninklijke Brill NV, Leiden, The Netherlands.

Desalinated water has become a legitimate alternative water resource for the irrigation of intensive crops in semiarid regions. The concentrations of calcium (Ca) and magnesium (Mg) in water (CCa and CMg, respectively) supplied from desalinated plants are much lower than the values typically found in irrigation water resources in semiarid regions. blossom-end rot (BER), a physiological disorder at the blossom-end part of the fruit resulting in tissue disintegration and dehydration, is considered a Ca-related disorder and therefore the optimization of CCa has to consider not only total fruit production but also the occurrence of BER. There is a lack of information regarding the optimal CCa and CMg and Ca/Mg ratio in low-salinity water under Mediterranean conditions for high-quality yield of tomato fruits.The main objective of the research was to optimize CCa and CMg for the production of high tomato fruit yield with minimal occurrence of BER. A secondary objective was to determine critical levels of Ca, Mg and Ca/Mg ratio in leaves in relation to yield and the occurrence of BER.Tomato plants were grown in an inert media and fed with a wide range of CCa and CMg. Fruit yield was shown to decrease significantly when CCa was at or below 0.40 mmol l-1. In moderate CMg (1.4 mmol l-1) treatment, BER was negatively correlated to Ca level up to and including 1.4 mmol l-1 and was not manifested above that level under the prevailing conditions. Elevating CMg above 0.25 mmol l-1 enhanced BER occurrence. Concentrations of Ca and Mg in tomato organs increased with the respective mineral concentration in irrigation solution, whereas each element was reduced in organs as a function of the increased solution concentration of the other. The Ca concentration in diagnostic leaves (the diagnostic leaf is the fully developed youngest leaf) for optimal fruit yield with minimum BER was found to be 1.6%. The optimum CCa for high fruit yield with minimal BER occurrence was found to be in the range of 1.5-2.5 mmol l-1 combined with CMg at 0.25 mmol l-1. © 2017 by Koninklijke Brill NV, Leiden, The Netherlands.

Background and Aims Stomatal morphology and function have remained largely conserved throughout ∼400 million years of plant evolution. However, plant cell wall composition has evolved and changed. Here stomatal cell wall composition was investigated in different vascular plant groups in attempt to understand their possible effect on stomatal function. Methods A renewed look at stomatal cell walls was attempted utilizing digitalized polar microscopy, confocal microscopy, histology and a numerical finite-elements simulation. The six species of vascular plants chosen for this study cover a broad structural, ecophysiological and evolutionary spectrum: ferns (Asplenium nidus and Platycerium bifurcatum) and angiosperms (Arabidopsis thaliana and Commelina erecta) with kidney-shaped stomata, and grasses (angiosperms, family Poaceae) with dumbbell-shaped stomata (Sorghum bicolor and Triticum aestivum). Key Results Three distinct patterns of cellulose crystallinity in stomatal cell walls were observed: Type I (kidney-shaped stomata, ferns), Type II (kidney-shaped stomata, angiosperms) and Type III (dumbbell-shaped stomata, grasses). The different stomatal cell wall attributes investigated (cellulose crystallinity, pectins, lignin, phenolics) exhibited taxon-specific patterns, with reciprocal substitution of structural elements in the end-walls of kidneyshaped stomata. According to a numerical bio-mechanical model, the end walls of kidney-shaped stomata develop the highest stresses during opening. Conclusions The data presented demonstrate for the first time the existence of distinct spatial patterns of varying cellulose crystallinity in guard cell walls. It is also highly intriguing that in angiosperms crystalline cellulose appears to have replaced lignin that occurs in the stomatal end-walls of ferns serving a similar wall strengthening function. Such taxon-specific spatial patterns of cell wall components could imply different biomechanical functions, which in turn could be a consequence of differences in environmental selection along the course of plant evolution. © The Author 2017.

Background and Aims: The aim of this research was to examine the effect of sustained and regulated deficit irrigation regimes on vegetative growth, physiological aspects and yield parameters of field-grown Merlot grapevines. Methods and Results: The 4-year trial (2009–2012) in a 13-year-old commercial vineyard of Vitis vinifera cv. Merlot compared the following irrigation treatments: three sustained deficit irrigation treatments and two regulated deficit irrigation treatments. We measured leaf area index and pruning mass to assess vegetative growth, and we recorded stem water potential and gas exchange parameters to examine vine water status. At harvest, we measured yield parameters, crushed berries and analysed must. High water availability during early berry development enhanced vegetative growth and increased berry size and yield. Reducing water supply in order to create a certain level of drought stress during late berry development did not damage yield or berry maturation. Conclusions: Regulated deficit irrigation treatment combining higher irrigation from flowering to bunch closure and lower irrigation from bunch closure to harvest has the potential to generate the best balance between vegetative growth, high yield and wine with enhanced colour and aroma compounds. Significance of the Study: This study demonstrates the implications of skilled irrigation, in particular the specific effect of irrigation alternation at different phenological stages. © 2016 Australian Society of Viticulture and Oenology Inc.

Eucalyptus silver dollar (Eucalyptus cinerea) is cultivated under intensive agronomic practices for production of cut foliage branches for the floriculture industry. A range of damage symptoms, suspected to be related to unoptimized mineral nutrition, routinely occur in the leaves at the production plantations and reduce yield quality. No information is available about the nutritional requirements of Eucalyptus silver dollar, or of any other Eucalyptus species under intense cultivation for cut foliage branches production. In this study we evaluated the hypotheses that: (1) leaf damage symptoms in the Eucalyptus silver dollar plantations might be related to the nutritional status of the leaves; and (2) they are affected by environmental and growing conditions, and will therefore differ between seasons and location of the plantations. To test these hypotheses we studied the seasonal and location variations in the ionomics of damaged and healthy leaves, physiological parameters, and postharvest attributes of cut foliage branches during vase life in four plantations of Eucalyptus silver dollar in Israel. The observed leaf symptoms were also characterized anatomically. The range of concentrations for individual macronutrients in the leaves was (in g kg-1): N (18-40); P (1.2-3.0); K (5.5-17.0); Ca (3.5-14.0); Mg (1.1-2.8); S (1.3-2.6). The concentrations range for micronutrients was (in mg kg-1): B (10-100); Fe (30-170); Zn (14-27); Mn (38-190); Cu (3.5-5.9). None of the identified leaf symptoms correlated with a consistent increase or decrease of the content of a specific mineral nutrient or heavy metal compared to the healthy leaves, suggesting that they were not caused by mineral deficiency or toxicity. The leaf ionomics was affected by season and varied between locations. The main damage symptoms observed in the four examined plantations during the four harvests were red and purple spots, and oil stains. Postharvest experiments showed that the quality of branches was reduced during 7-15 days of vase life following transport simulation to the local market. The degree of reduced quality during vase life was also dependent on the location of the plantation and the season of harvest. The oil stains appeared in the two most southern locations during summer, suggesting that this symptom might be derived from the summer conditions such as the high temperatures and high light intensities occurring in the southern part of Israel. © 2017 by Koninklijke Brill NV, Leiden, The Netherlands.

Question: What are the controls on biomass production and species diversity in Mediterranean grasslands? Do medium-term (i.e. inter-annual) precipitation legacy effects on biomass production and diversity occur in these grasslands?. Location: Karei Deshe Experimental Range Station, Upper Galilee, northern Israel. Methods: We used a long-term (21-r) cattle-grazing experiment in a Mediterranean grassland to search for evidence of precipitation legacies on herbaceous above-ground biomass production and species diversity. Biomass production was measured in two seasonal late grazing treatments, in the winter and at peak vegetative production in the spring, while species diversity was determined at peak production. We used ANCOVA to test the effects of residual biomass, previous year's stocking density and previous year's biomass on current biomass production. We ran forward selection and ANCOVA to test for precipitation legacies, using precipitation variables relating to both previous and current year's rainfall. In addition we examined linear regressions of biomass and species diversity on current year's precipitation. Results: Biomass production and species diversity showed weak to negligible relationships with current year's precipitation. Biomass production, and to a lesser extent, diversity, were affected by inter-annual fluctuations in growing conditions. However, evidence of inter-annual precipitation legacies were found only for early season biomass production, and not for peak biomass production or species diversity. We found no effect of grazing on biomass production at the onset of the grazing season, regardless of important differences in previous year's stocking density. Additionally, we found no effect of previous year's biomass production or stocking density on the following year's biomass or diversity, but peak biomass production was strongly related to previous year's residual biomass. Conclusions: The lack of an inter-annual precipitation legacy on peak biomass production contributes to a growing body of evidence showing that Mediterranean ecosystems are unique among semi-arid and sub-humid ecosystems, where precipitation legacies play an integral role. Mediterranean ecosystems are unique in their combined long-term high variability in rainfall and long grazing history. This lack of precipitation legacy led to the development of vegetation that is highly resistant to inter-annual fluctuations in growing conditions. We propose that the high resistance contributes to the lack of inter-annual, or medium-term, precipitation legacies on the studied grassland, and may contribute to its persistence under future projected climate change in the region. © 2016 International Association for Vegetation Science