Leaf starch and nutrient responses to stem girdling and drought stress with respect to understanding HLB (greening) symptoms in citrus

The most important problem in world citrus production is the bacterial disease Huanglongbing (HLB; greening) which is caused by a phloem-limited bacterium that is vectored by a phloem-feeding psyllid. The earliest visible symptoms of HLB in leaves are an asymmetrical chlorosis referred to as "blotchy mottle", thought to be from starch accumulation from a phloem dysfunction and a decline in root health. We tested the hypothesis that such visible symptoms are not unique to HLB by stemgirdling two year-old seedling trees of 'Cleopatra' mandarin and 'Swingle' citrumelo rootstocks in the greenhouse. Girdling induced a 4-fold greater starch concentration in leaves on well-watered trees while star…

Phloem and xylem flow contributions to nectarine fruit development

This study aimed at determining how source-sink balance and phloem/xylem flows affect nectarine fruit growth during development. Different levels of water and assimilate availability to growing fruits were induced in vivo by varying leaf:fruit ratio (L:F) of fruiting shoots and by interrupting the phloem stream (girdling) at the base of entire fruiting shoots. Two fruiting shoots in each of six ‘Big Top’ adult nectarine trees were selected, labeled and their L:F was adjusted by thinning fruits or removing leaves to two levels: high L:F and low L:F. Stem water potential, stomatal conductance, continuous fruit diameter and leaf turgor pressure were measured before and after girdling at stage …

Effects of partial rootzone drying and rootstock vigour on growth and fruit quality of 'Pink Lady' apple trees in Mediterranean environments

We investigated the effects of partial rootzone drying (PRD) and rootstock vigour on water relations, and vegetative and productive performance of ‘Pink Lady’ apple (Malus domestica Borkh.) trees in central Sicily. In a first field trial, trees on MM.106 rootstock were subjected to: Conventional irrigation (CI), maintaining soil moisture above 80% of field capacity; PRD irrigation, where only one alternated side of the rootzone received 50% of the CI irrigation water; and continuous deficit irrigation (DI), where 50% of the CI water was equally applied to both sides of the rootzone. In a second trial, trees on M.9 or MM.106 were subjected to CI and PRD irrigation. PRD reduced stomatal condu…

Changes in quality parameters and volatile aroma compounds in 'fairtime' peach during fruit development and ripening

Responses of Prunus ferganensis, Prunus persica and two interspecific hybrids to moderate drought stress

Prunus ferganensis (Kost. & Riab) Kov. & Kost, a close relative of the cultivated peach (Prunus persica (L.) Batsch.), is native to arid regions of central Asia and may possess traits valuable for improving drought tolerance of commercial peach varieties. One distinguishing feature of P. ferganensis is its prominent, elongated, unbranched leaf venation pattern, which behaves as a simple recessive trait in segregating populations of P. ferganensis x P. persica hybrids. To understand whether this trait could be used as a marker in breeding for drought tolerance, we investigated the association between leaf morphological and physiological parameters related to drought response in P. ferganensi…

METABOLIC PROMOTERS AFFECT YIELD AND FRUIT QUALITY OF 'SANFILIPPARA' AND 'TRABIA' LOQUAT

Preliminary field trials with foliar applications of phenylalanine, methionine, oxylipins and sugars have shown improvements of external color, sugar content and uniformity of maturation in grapes, pome fruits, tomatoes and melons. In this study, we hypothesized that similar improvements could be obtained both in fruit of ‘Trabia’ and ‘Sanfilippara’ loquat (Eriobotrya japonica Lindl.) with applications of a commercial formulate called Sunred (Biolchim, Bologna, Italy) and containing various concentrations of the above metabolic promoters. The study was conducted on 12 ‘Sanfilippara’ and 12 ‘Trabia’ adult loquat trees grown in an orchard near Palermo, Italy. Half of the trees…

Water status and gas exchange of pistachio trees under different irrigation levels

The aim of this study was to investigate the physiological responses of pistachio trees to varying water supply in the attempt to identify reliable parameters to manage irrigation. Three different irrigation regimes were applied to 25-year-old pistachio trees of cultivar 'Bianca' on P. terebinthus rootstock. Midday stem water potential (ΨSWP), leaf relative water content (RWC), light-saturated net CO2assimilation (An), stomatal conductance (gs), and ambient conditions were monitored throughout the season, and light response curves of net photosynthesis were constructed. To reflect tree water status, trees were separated into three classes of ΨSWP, no deficit (ΨSWP> -1.5 MPa), mild defici…

Fruit yield and quality responses of apple cvars Gala and Fuji to partial rootzone drying under Mediterranean conditions

SUMMARYIncreasing irrigation efficiency is a major goal for fruit production in dry Mediterranean environments. The present study was conducted in three consecutive years (2007–09) under typical Mediterranean conditions and tested the effect of partial rootzone drying (PRD) on yield and fruit quality of two apple cultivars: Gala, with fruit maturing in summer and Fuji, with fruit maturing in autumn. Three irrigation treatments were imposed: conventional irrigation (CI), PRD (0·50 of CI water on one side of the rootzone, which was alternated periodically) and continuous deficit irrigation (DI, 0·50 of CI water on both sides of the rootzone). During the 2008 and 2009 irrigation seasons, DI re…

Preliminary evaluation of sixPrunusrootstocks for peach in Italy

In Italy, the evaluation of rootstocks is supported by the Ministry of Agriculture and carried out in a network of trials along the Country. This study evaluated growth and yield performance of ‘Big Top’ nectarine and ‘Rome Star’ peach grafted on six rootstocks of different origin and vigor, namely GF677 (the most widespread in Italy), Garnem, Adesoto, RootPac®20, RootPac®40, and RootPac®90, in three different locations, Castelvetrano (Sicily), Forlì and Cesena (Emilia-Romagna). Yield, number of fruits, trunk cross-sectional area (TCSA), average fruit weight, flesh firmness, soluble solids content (SSC) and titratable acidity (TA) were determined at the third leaf (2015). In all sites, tree…

The effect of saline water on Phillyrea angustifolia L. seedlings

Water limitations in the Mediterranean areas are very common and the use of saline water for plant irrigation is becoming a necessity. Salinity generally affects plant growth and physiological processes, and can eventually lead to leaf injuries and plant death. For these reasons, the selection of salt tolerant species is a priority for landscaping purposes in the Mediterranean areas. The objective of this study was to evaluate the effect of saline water on Phillyrea angustifolia plant performance. Seventy-five rooted cuttings were grown in the greenhouse in 4-liter pots and irrigated for 5 months with saline water at different NaCl concentrations for two consecutive years. In 2010, 45 plant…

Growth, yield and fruit quality of 'Tropic Snow' peach on size-controlling rootstocks under dry Mediterranean climates

Abstract A six-year trial was carried out to evaluate the vegetative and productive performance of low-chill, early-ripening ‘Tropic Snow’ peach grown on five peach × almond rootstocks, different for their vigor. The study was conducted in south-western Sicily using 45 V-trained peach trees planted in 2005 and grafted on GF677, the most common rootstock in Sicily, and four low-vigor rootstocks selected at the Department of Agricultural, Food and Environmental Sciences, University of Pisa, namely IS5/8 (Polluce), IS5/19 (Castore), IS5/23, and IS5/29. Trunk circumference, winter and summer pruning weight, total number and weight of fruits per tree, and major fruit quality traits were recorded…

Field non-destructive determination of nectarine quality under deficit irrigation

This study investigated the effects of deficit irrigation (DI) at different fruit growth stages and tree orientation on fruit quality of ‘September Bright’ nectarines (Prunus persica L. Batsch). Control trees were fully irrigated throughout the entire fruit development period, whereas deficit irrigation was supplied at fruit growth stage I (cell division, DI-I), II (pit hardening, DI-II), IIIa (cell expansion, DI-IIIa) and IIIb (fruit maturation, DI-IIIb). Non-destructive measurements of fruit maturity and quality were carried out using portable devices based on near-infrared spectrometry and pigment fluorescence on west- and east-oriented trees of an Open Tatura system. Chlorophyll degrada…

Effect of soil permanent grass cover on growth, yield and water status of rainfed olive trees in Sicily

The study was carried out in an olive grove located along the hills of northern Sicily where soil had been managed for decades by chemical weeding. Starting in 2008, one portion of the grove was left non-weeded, and the permanent grass cover was managed by mowing 2-3 times per year in winter and spring. In 2011, 2012 and 2013, yield, average drupe weight, percentage of drupe black color (veraison), trunk circumference, shoot elongation, and leaf relative water content (RWC) were determined on 34 adult trees of the cultivar 'Biancolilla' with uniform size and age. In 2013, soil organic matter content and leaf nutrient concentrations were also determined in the two portions of the grove. As e…

Deficit irrigation and maturation stage influence quality and flavonoid composition of ‘Valencia’ orange fruit

BACKGROUND:Effects of continuous deficit irrigation (DI) and partial rootzone drying (PRD) treatments (50%ETc) in comparison with full irrigation (CI, 100% ETc) were investigated during ‘Valencia’ orange fruit maturation. Ultra-high-performance liquid chromatography/high-resolutionmass spectrometry was used to quantify hesperidin, narirutin, tangeritin, nobiletin, didymin and neoeriocitrin in the fruit juice and peel. RESULTS: No significant effect of irrigation was found on yield, juice soluble solids or acidity. Juice color was not influenced by irrigation or harvest date, whereas peel color increased during maturation and was more pronounced in CI and PRD fruits. Juice acidity reached a …

Evaluation of Small Vase and Y-trellis Orchard Systems for Peach and Nectarine Production in Mediterranean Regions

Two peach planting systems, Small Vase (SV) and Y-trellis (Y), were evaluated and compared in the Mediterranean settings of Southern Italy. The two orchards were located next to each other on relatively uniform soil and terrain, and the observations included two peach (‘Rich May’ and ‘Summer Rich’) and two nectarine (‘Big Bang’ and ‘Nectaross’) cultivars. In the SV system, trees were spaced at 4.5 A— 2.5 m (888 trees/ha), whereas in the Y system, trees were spaced at 5.5 A— 2 m (909 trees/ha) and no canopy gap was left between rows. Yield per tree; fruit size grade; unit price of sold peaches for each size grade; materials, labor and associated costs for cultural management;…

Early bearing and vegetative growth of 153 Sicilian olive accessions

In 2014, an olive germplasm collection was established in south-western Sicily, Italy. The collection included 153 Sicilian accessions and 3 international varieties (reference), each with 7 trees, spaced at 5×2 m and trained to hedgerow system. The aim of the trial was to study early growth and yield responses of the accessions to super-high planting density (SHD). Trunk cross sectional area, tree height, pruning weights, shoot positioning, blooming and fruit yield (kg tree-1) were measured in 2015 and 2016. Based on trunk growth and amount of prunings, the 153 accessions were separated into four categories of vigor as it follows: very high vigor (6 accessions), high vigor (13), medium vigo…

GROWTH AND BIOMASS PARTITIONING OF YOUNG LOQUAT PLANTS UNDER WATER DEFICIT

Water scarcity in the Mediterranean areas is very common and understanding responses to drought is important for loquat management and production. The objective of this study was to evaluate the effect of water deficit on growth and biomass partitioning of loquat. Ninety 1-year-old plants of 'Marchetto' loquat (Eriobotrya japonica Lindl.) grafted on quince were grown in the greenhouse in 12-liter pots and three water regimes were imposed starting on 11 May and until 27 July, 2013. One-third of the plants was irrigated to reintegrate 100% of the water consumed (CTR); a second group of plants was irrigated with 66% of the water consumed by CTR plants (MD); a third group was irrigated with 33%…

Mannitol-producing tobacco exposed to varying levels of water, light, temperature and paraquat

Transgenic mannitol-producing (+mtlD) and wild-type (-mtlD) tobacco plants were exposed to water deficit, varying light intensities, low temperatures, and paraquat applications to test whether mannitol was involved in protection against abiotic stresses. In the water deficit experiment, -mtlD and +mtlD plants were fully irrigated [100% evapotranspiration (ET)] or received 25% ET for 40 d. Water deficit reduced the relative water content (RWC) of both types of plant starting on day 22 and the total stem length (TSL) of -mtlD 25% ET plants after 11 d, whereas TSL of +mtlD 25% ET was reduced only after 34 d. After 30 days of water deficit, a higher percentage of mature foliage was retained by …

Growth and biomass partitioning of Arbutus unedo, Laurus nobilis, Phillyrea angustifolia and Rhamnus alaternus seedlings under water deficit

Water scarcity in the Mediterranean areas is very common and the selection of drought tolerant species is a priority for landscaping purposes in the Mediterranean areas. The objective of this study was to evaluate the effect of water deficit on growth and biomass partitioning of Arbutus unedo, Laurus nobilis, Phillyrea angustifolia and Rhamnus alaternus. Seventy-two seedlings per species were grown in the greenhouse in 4-liter pots and three water regimes were imposed starting on 6 April and until 9 June, 2010. One-third of the plants was well irrigated to maintain soil water content in the 25-35% range (CTR); a second group of plants was deficit-irrigated to maintain soil water content in …

Transpiration/Evaporation Ratio in Prunus Fremontii and Marianna 2624 over a 4-Day Period of Drought

Drought stress represents one of the major environmental limitations to crop production in a large portion of the Earth’s surface. Natural genetic resources are one of the most powerful weapons against environmental stress. In such contest, the behavior in terms of water loss of two species, P. fremontii (slower-growing) and Marianna 2624 (faster-growing), native to arid and humid regions respectively, was tested. Transpiration (T) and evapotranspiration (ET) rates and soil water content (SWC) were measured in the two species under controlled conditions. Evaporation rate from the soil surface was obtained by difference, and an average transpiration/evaporation ratio (T/E) was calculated to …

Effects of rootstock vigour and in-row spacing on stem and root growth, conformation and dry-matter distribution of young apple trees

The effects of M.9 and MM.106 rootstocks and in-row spacing (0.4, 0.7, and 1 m) on the vegetative behaviour of three-year-old apple (Malus domestica Borkh) trees were studied. Analysis of digital i...

Fruit quality and flavor compounds before and after commercial harvest of the late-ripening ‘Fairtime’ peach cultivar

ABSTRACT In this work quality of tree ripe and commercial ripe ‘Fairtime’ peach fruit was evaluated during fruit maturation and storage. Quality parameters and volatile fraction were monitored at intervals of 7-15 days from pit hardening until 10 days after commercial harvest and after 7, 17 and 24 days of refrigeration. In fruit on the tree, weight increased quadratically, diameter and peel color increased linearly, whereas flesh firmness decreased linearly. Soluble solids (SS) reached maximum levels at commercial harvest, whereas acidity started declining after commercial harvest. In the peel, esters and alcohols showed opposite trends. In the flesh, alcohols decreased quadratically and d…

Diurnal irrigation timing affects fruit growth in late-ripening nectarines

Little is known about the best diurnal irrigation timing for maximum fruit growth in stone fruit, despite fruit size being the most important focus for growers to achieve maximum marketable yield. This study investigated the effects of morning and afternoon irrigation on nectarine fruit growth in stage I (cell division) and stage III (cell expansion). In the 2017/18 season, ‘September Bright’ trees were subjected to morning (Iam) and afternoon (Ipm) irrigations. Fruit diameter was monitored continuously (15-min intervals) using fruit gauges and converted into fruit weight, relative growth rate (RGR) and fruit growth efficiency (FGE), with the latter representing RGR per unit of crop water s…

Vegetative and productive responses of ‘Conference’ and ‘Williams’ pear trees planted at different in-row spacings

Abstract The effect of in-row spacing on the vegetative and productive performance of 4-year-old ‘Conference’ (CON) and ‘Williams’ (WIL) pear trees was studied. Analysis of digital images was used to estimate canopy growth and conformation. Fruit quality was determined by measuring fruit weight, flesh firmness, peel color, soluble solid content, and titratable acidity. WIL produced more and more efficiently than CON, especially at closer spacings. WIL canopies were generally bigger than CON canopies, and reduced spacing penalized stem growth and influenced canopy conformation. Root growth and conformation was similar for both cultivars, whereas decreasing in-row spacing reduced root dry wei…

Growth and physiological responses of young olive trees affected by Olive leaf yellowing associated virus

We studied the effect of Olive leaf yellowing associated virus (OLYaV) on biometric and physiological changes in olive. The trial was carried out on 32 two-yearold virus-free trees of 'Frantoio' grafted on virus-free olive seedlings and grown in 32-L pots. Half of the trees were inoculated with OLYaV in the fall of 2007. At 6, 18, and 24 months after inoculation, tree height, basal trunk diameter and total leaf number were determined, and leaf area tree-1 was estimated from a 50-leaf subsample. Twigs of various order were also counted and measured. At the end of the experiment, dry matter partitioning, leaf gas exchange and water potential were also measured. Total twig length and number, t…

Effects of partial rootzone drying and rootstock vigour on dry matter partitioning of apple trees (Malus domesticacvar Pink Lady)

SUMMARYThe effects of partial rootzone drying (PRD) and rootstock vigour on dry matter accumulation and partitioning among leaves, shoots, fruits, frame and roots of apple trees (Malus domesticaBorkh. cvar Pink Lady) were investigated in 2005 near Caltavuturo, in Sicily. In a first field trial, trees on MM.106 rootstock were subjected to: conventional irrigation (CI), maintaining soil moisture above 0·80 of field capacity; PRD irrigation, where alternating sides of the rootzone received 0·50 of the CI irrigation water; and continuous deficit irrigation (DI), where 0·50 of the CI water was equally applied to both sides of the rootzone. In a second trial, trees on M.9 or MM.106 were subjected…

Transpiration rates and hydraulic conductance of two olive genotypes with different sensitivity to drought

Although some mechanisms of leaf dehydration tolerance are known in olive (Olea europaea L.), insights on adjustments in stem and root hydraulic conductance (K) in response to drought are yet to be explored. This work investigated transpiration mechanisms and K regulations in two olive genotypes showing different sensitivity to drought stress. In 2017, one-year-old potted ‘Nocellara del Belice’ (NB) and ‘Cerasuola’ (CE) plants were set in a greenhouse and double-bagged to avoid evaporation from soil surface. Half of the plants were drought-stressed (DS, no irrigation) for more than 30 days and the remaining plants were well-watered (WW). At the end of the drought period, stem and root porti…

Growth, Yield and Fruit Quality of 'Peluche' Loquat under Windbreak Nets.

The advantages of protecting 6-year-old ‘Peluche’ loquat trees (Eriobotrya japonica Lindl.) with nets were investigated in Sicily. Vegetative and reproductive growth were measured on 20 trees under net protection and 20 in open field conditions. A neutral, 50% windbreak net (yielding 70% of light penetration) was positioned around the field and above trees to cut down wind action and other occasional extreme atmospheric phenomena. Side openings were left on the nets to provide the entrance for pollinators. Compared to trees in the open field, trees under nets showed increased vigor (trunk cross-sectional area) and fruit growth (relative growth rate), and higher yields due also to larger fru…

Growth, fruit yield and quality of ‘Golden Delicious’ apple trees under fixed partial rootzone drying

Climatic Characterization and Phenology of Local Peach Genotypes in the Udzungwa Uplands of Tanzania

The phenology of two local peach genotypes was studied to verify whether peaches can be produced in the Tanzanian uplands. Observations were conducted on trees of one early- and one late-ripening peach genotype in 2010 and 2011. Temperature trends were reconstructed and three chilling estimation models were tested. The two peach genotypes differed for timing of flower and leaf bud-break. Common symptoms of insufficient chilling (presence of numerous stages at a specific date and about 20% of undeveloped flower buds) were observed in the late genotype. Both Utah and Dynamic models indicated low chilling accumulation, lower than the Mean Temperature model in most cases. This is inconsistent w…

Recurrent deficit irrigation and fruit harvest affect tree water relations and fruitlet growth in ‘valencia’ orange

Background – Partial rootzone drying is an irrigation strategy known for increasing water use efficiency without significantly affecting tree water status. ‘Valencia’ oranges have a very long development period and nearly mature fruit and new fruitlets may be present at the same time on the tree, competing for water and assimilates. Objectives – The present study investigates the effect of recurrent deficit irrigation and fruit harvest on tree water status and fruitlet growth of ‘Valencia’ orange. Methods – Forty-eight adult trees were exposed to three irrigation treatments for seven years (2007–2013): irrigation with 100% of ETc (CI), continuous deficit irrigation (DI, 50% of CI) and parti…

LOW VIGOR PEACH × ALMOND ROOTSTOCKS FOR INTENSIVE PEACH PLANTINGS IN MEDITERRANEAN ENVIRONMENTS

A three-year trial was carried out to evaluate the vegetative and productive performance of five peach rootstocks of varied vigor. The study was conducted in south-western Sicily using 45 V-trained trees of 'Tropic Snow' peach planted in 2005 and grafted on GF677 and four low-vigor rootstocks selected at the Department of Agricultural, Food and Environmental Sciences, University of Pisa, namely IS5/8 (Polluce), IS5/19 (Castore), IS5/23, IS5/29. Trunk circumference, winter and summer pruning weight, number and mass of fruit were recorded from 2010 to 2012. All IS selections reduced trunk cross-sectional area (TCSA) and pruning weight compared to GF677 with IS5/23 inducing the highest reducti…

Continuous detection of new plant water status indicators in stage I of nectarine fruit growth

Conventional irrigation management is often inefficient in responding to seasonal changes of tree water needs. The use of leaf- and fruit-based sensors might provide helpful insights on tree water status, although they have been poorly investigated so far. Fruit gauges and leaf patch clamp pressure (LPCP) probes were tested during stage I of nectarine fruit growth to evaluate if leaf turgor pressure and fruit size may serve as indicators of water deficit. This experiment was carried out in the 2017/18 season. Four irrigation levels were applied to ‘September Bright’ nectarine trees (100, 40, 20 and 0% of crop evapotranspiration, ETc) and data were collected during stage I of fruit growth. T…