Tolerant Rootstocks Research Articles

A real-time PCR assay for detection and absolute quantitation of Citrus exocortis viroid in two sensitive and tolerant rootstocks

Citrus exocortis viroid (CEVd) is the causal agent of exocortis disease, the economically important viroid disease of citrus. In this research, CEVd copy number was quantified in sour orange (Citrus aurantium L.) and citrange (Poncirus trifoliata L. Raf. × Citrus sinensis L.) seedlings by absolute real-time PCR. A full-length in vitro transcript of a single-sequence CEVd-S1 variant was synthesized and mechanically inoculated into sour orange and Troyer citrange seedlings as tolerant and sensitive hosts, respectively. CEVd copy number was subsequently monitored at different times after inoculation in the green bark of infected seedlings for up to 16 weeks post inoculation (wpi). CEVd was detected at 3 wpi and totally increased up to 16 wpi. The copy number of CEVd per milligram of bark tissue in both host species was in the range of 103 to 104 at the third and sixth weeks post inoculation, without any significant differences. Although the viroid titer was remarkably higher in citrange (sensitive host) than in sour orange (tolerant host) at 10–16 wpi, we demonstrated that CEVd titer differed in citrus species depending on the time of sampling and host plant species.

Multi-parameter characterization of water stress tolerance in Vitis hybrids for new rootstock selection

Drought in grapevine could be faced using tolerant rootstocks. The present work aims at the evaluation of 25 new genotypes potentially tolerant to drought by using recent methods of phenotypical screening (thermography and on-solid reaction spectroscopy). Plants were grown in well-watered and stressed field conditions. Proxi for transpiration, wood hydrophobicity and starch content were used to characterize and classify the genotypes. The predominant role of the environment was highlighted, nevertheless genotype and genotype × environment interaction showed significant variations as well. Hybrids were classified based on their steady, susceptible or adaptable behavior. The 14 most promising genotypes were identified, 5 of them showing two tolerance mechanisms. In the future, results from this experiment will support viticulture in water limited areas releasing new drought-tolerant interspecific hybrids to be tested after grafting with different scions.

Tolerance of apple rootstocks to short-term waterlogging

ABSTRACT: Until few years ago there were limited options of apple rootstocks commercially available for Brazilian growers; although, new series of Geneva® rootstocks introduced recently present desirable features such as vigor control and wider lateral branch angle. On the main apple producing regions of Brazil, intermittent rainfall eventually occurs and waterlogged condition is frequent especially in high clay oxisols; in addition, little is known about the tolerance of rootstocks M.9, Marubakaido/M.9 interstock, G.202, G.213 and G.814 to waterlogging. Thus, the objective of this experiment was to evaluate the tolerance of these rootstocks to short-term waterlogging on root and aerial parameters. Potted ‘Maxi Gala’ apple plants were kept under 48 hours of waterlogging weekly throughout 19 weeks to be compared with a normal hydric condition control. The evaluated variables were: leaf, stem and root dry matter, number and length of new root emission, and number of leaves, mean leaf size and chlorophyll content. Rootstocks G.202, G.814 and Marubakaido/M.9 interstock presented more tolerance to waterlogging, and the main defense mechanism was the emission of new adventitious roots.

Field susceptibility of cork oak trees with different provenances to Phytophthora cinnamomi

AbstractCork oak decline has been a serious problem in Portuguese central and southern areas in the last 30 years. This decline is associated with Phytophthora cinnamomi, a pathogen with a major impact on cork oak decline. A programme aiming the plant selection on resistance, to address the infection of soilborne P. cinnamomi in cork oak woodlands, should therefore be fundamental for an integrated strategy for the management of the cork oak woodlands. In this context, the main objective of this study was to select potential tolerant families by evaluation of field susceptibility to the pathogen. During 10 years (2004–2014), the survival and height growth of 157 cork oak families from eight different provenances from Portugal and Spain were assessed in a field highly infested with P. cinnamomi. Results showed a high mortality of the plants, over the whole period, insofar that only 14 families, out of the 157, showed a survival rate between 40% and 60%. These families exhibited also a good height growth with heights ranging between 1 and 1.50 m. It was also observed that ploughing, leading to better soil conditions, could contribute to improve the survival rate and the development of plants. Potential families of cork oak were identified as tolerant plant material and rootstock, thereby candidates to be used in restoration and reforestation. Interestingly, additional results concerning a Quercus faginea family evidenced a good resistance of this species to the pathogen. This information is indicative that Q. faginea could be used as a rootstock for the cork oak reforestation in areas where the pathogen had high impact.

Drought tolerance in citrus rootstocks is associated with better antioxidant defense mechanism

Citrus is one of the major fruit crops grown worldwide. Citrus trees are affected by different abiotic stresses including drought which decrease its yield. In this study, six different citrus rootstocks (Volkameriana lemon, Brazilian sour orange, Carrizo citrange, Eureka lemon, Gada dahi, and Rangpur lime) were subjected to drought stress (24 days) and leaf relative water content (LRWC), chlorophyll 'a' and 'b', antioxidant capacity (AC), total phenolic content, and proline content (PRO) were measured. Hydrogen peroxide (H2O2), lipid peroxidation (MDA), total soluble proteins (TSP), and enzymatic antioxidant activities, such as superoxidase dismutase (SOD), catalase (CAT), and peroxidase (POD), were measured in leaves and roots of the rootstocks. Drought-stressed Volkameriana lemon had the minimum LRWC but higher SOD activity in its leaves. Carrizo citrange possessed the minimum amount of Chl 'a' and 'b' in leaves and exhibited lesser MDA and H2O2 in roots but greater TSP content in leaves and roots. SOD, CAT, POD, PRO, MDA, H2O2, and AC decreased in the leaves of Eureka lemon and Rangpur lime under drought stress. MDA and H2O2 contents were observed higher in leaves of Brazilian sour orange (a drought sensitive rootstock). However, higher SOD activity in roots and higher CAT and POD activities in leaves and roots were recorded in Carrizo citrange (a drought-tolerant rootstock). The results indicated that all the studied rootstocks were different in their defense mechanism. Tolerant rootstocks exhibited less amount of MDA and H2O2 and more antioxidant enzymatic activities (SOD, CAT, and POD) to cope with reactive oxygen species produced during drought stress.

Molecular Characterization and Genetic Relationships of Some Stress Tolerant Grape Rootstock Genotypes as Revealed by ISSR and SSR Markers

Grapevine rootstocks are a complex group of plants; most of them are interspecific hybrids evolved using parent genotypes having inherent tolerance to biotic and abiotic stresses. Fifteen species and interspecific hybrids of grape rootstocks along with three Vitis vinifera cultivars from IARI germplasm unit were analyzed with ten ISSR and seven SSR primers combinations. These ISSR produced 69 scorable bands with band size ranged from 200 to 1500 bp, PIC from 0.66 to 0.86 and primer heterozygosity ranged from 0.71 to 0.88. While, SSR primers detected a total of 24 alleles across 15 genotypes with PIC from 0.43 to 0.78 and primer heterozygosity from 0.49 to 0.81.The genetic similarity among the 15 grape genotypes using ISSR and SSR ranged from 0.27 to 1.00 in ISSR and 0.05 to 1.00 in SSR analysis. The genetic similarity matrices using ISSR analysis ranged from 27.0 to 85.0% and SSR 5.0 to 83.0%, respectively. The Vitis species Dogridge and Salt Creek had the highest similarity coefficient of 85% with ISSR analysis, while the interspecific hybrids 1103 Paulsen and 110 Richtier had the maximum similarity coefficient of 83% as identified by SSR analysis. The two marker systems formed two main clusters which were almost similar to that of PCA values. The principal coordinate analysis further helped in depicting the variability among species and hybrids of grape genotypes in three dimensional modes. In case of ISSRs, the first three coordinates accounted 51.92% for the existing variability, while with SSRs the variability accounted is 59.69%. The results revealed that ISSR and SSR markers could be exploited for genetic diversity analysis among the highly heterozygous grape rootstock species and interspecific hybrids.Plant Tissue Cult. & Biotech. 28(1): 77-90, 2018 (June)

Root proteomic and metabolic analyses reveal specific responses to drought stress in differently tolerant grapevine rootstocks

BackgroundRoots play a central role in plant response to water stress (WS). They are involved in its perception and signalling to the leaf as well as in allowing the plant to adapt to maintaining an adequate water balance. Only a few studies have investigated the molecular/biochemical responses to WS in roots of perennial plants, such as grapevine. This study compares two grapevine rootstock genotypes (i.e. 101.14 and M4) with different tolerance to WS, evaluating the responses at proteomic and metabolite levels.ResultsWS induced changes in the abundance of several proteins in both genotypes (17 and 22% of the detected proteins in 101.14 and M4, respectively). The proteomic analysis revealed changes in many metabolic pathways that fitted well with the metabolite data. M4 showed metabolic responses which were potentially able to counteract the WS effects, such as the drop in cell turgor, increased oxidative stress and loss of cell structure integrity/functionality. However, in 101.14 it was evident that the roots were suffering more severely from these effects. We found that many proteins classified as active in energy metabolism, hormone metabolism, protein, secondary metabolism and stress functional classes showed particular differences between the two rootstocks.ConclusionThe proteomic/metabolite comparative analysis carried out provides new information on the possible biochemical and molecular strategies adopted by grapevine roots to counteract WS. Although further work is needed to define in detail the role(s) of the proteins and metabolites that characterize WS response, this study, involving the M4 rootstock genotype, highlights that osmotic responses, modulations of C metabolism, mitochondrial functionality and some specific responses to stress occurring in the roots play a primary role in Vitis spp. tolerance to this type of abiotic stress.

Towards developing a metabolic-marker based predictive model for Phytophthora nicotianae tolerance in citrus rootstocks

Root rot of citrus trees caused by Phytophthora nicotianae is responsible for severe economic losses in citriculture. Use of resistant rootstocks is an effective method of managing this problem, however, breeding and selection of new citrus rootstocks is a time-consuming undertaking. The objective was to develop a method for the rapid assessment of rootstocks for P. nicotianae tolerance, using a metabolomics approach to identify metabolic markers for the phenotypic trait of tolerance. Sixteen citrus rootstocks were inoculated with P. nicotianae in the greenhouse for determination of relative tolerance/susceptibility. Healthy citrus roots from four tolerant and four susceptible rootstocks were used for metabolite analysis with the objective of identifying potential biomarkers. Organic solvent extractions of the roots were prepared and analysed by mass-spectrometry based liquid chromatography, which produced 367 ion features (retention time and m/z). Orthogonal partial least squares discriminant analysis of peak abundance using MarkerLynx software allowed for the identification of ion features that differentiate tolerant and susceptible rootstocks. Using descriptive and inferential statistics based on the ion features of uninoculated tolerant vs. susceptible rootstocks, applying logistic regression, 14 top markers were identified and two of them (22.03_259.0975 and 22.21_313.1445: retention time (rt) and mass to charge ratio (m/z) were accepted as potential metabolic markers. A model that can potentially predict tolerance in citrus rootstocks with >98% accuracy is presented.

Response of the citrus rootstock genotypes against artificial inoculation of Phytophthora nicotianae

Effect of Phytophthora nicotianae Breda de Haan pathogen on different rootstock genotypes including sour orange, Troyer citrange and six variants of C. jambhiri Lush, viz. RLC-5, RLC-6, RLC-7, Grambhiri, rough lemon and Italian rough lemon were studied. Of the various rootstocks, Phytophthora inoculation tended to show significantly maximum plant height in Grambhiri (30.45cm). Significantly highest leaf numbers/plant (30.45), fresh root mass (4.13g) and dry root mass (2.47g) were recorded in the infected plants of RLC-5, however, it was statistically similar with sour orange, Italian rough lemon and Troyer citrange for leaf numbers, RLC-6 and Grambhiri for fresh root mass and RLC-6 and Italian rough lemon for stem diameter. RLC-6 had the highest stem diameter (3.62 cm) without having significant difference with RLC-5, RLC-7 and Italian rough lemon. After fungal inoculation, Troyer citrange showed the highest feeder root volume (2.45 cm3) followed by sour orange. These two rootstocks also prove superiority to have the highest photosynthetic rate (A) and transpiration rate (E) over other infected genotypes of citrus rootstocks tested. Except Italian rough lemon and rough lemon, all the rootstocks were found similar statistically in respect of stomatal conductance (gs). Overall,Troyer citrange proved best, and showed the lowest reduction in growth and physiological attributes after fungal inoculation. Being a Phytophthora tolerant rootstock, Troyer citrange was considered the standard rootstock to study the per cent change in disease incidence and feeder root infection in other genotypes, which indicated sour orange to be the next best rootstock. Of the six variants of Italian rough lemon, RLC-5 and RLC-6 tended to show the lower root infection than rest of the variants studied.

Boron deficiency and toxicity altered the subcellular structure and cell wall composition architecture in two citrus rootstocks

Abstract Trifoliate orange and citrange are two important rootstock resources to citrus, and citrange has a stronger tolerance to boron (B) deficiency and toxicity than trifoliate orange. In this study, we described how B deficiency and toxicity depressed the variations of cell wall B location, subcellular structure, cell wall components and structure of the two citrus rootstocks, to evaluate the mechanisms of different B tolerance of rootstocks on the cellular and structural levels. The results showed that citrange had better growth and lower symptoms of B stresses than trifoliate orange. What is more, citrange had a stronger ability to allocate more B to cell walls than trifoliate orange at deficient-B level. Under B deficiency and excessive conditions, severe damages in subcellular structure with obvious irregular thickening of cell walls and higher accumulation of plastoglobulus were observed in leaf cells of both two rootstocks. Additionally, it also showed obvious variations in the mode of hydrogen bonding, and more accumulation of cellulose, phenols and carbonhydrates in cell walls of trifoliate orange leaf under B starvation, while lighter changes on cell wall components were observed in citrange. As for B toxicity, comparing to trifoliate orange, citrange showed a lighter damage on pectin crosslinking structure in cell walls of leaf tissue. These results gained some novel mechanisms of different citrus rootstocks to B stress tolerance, and provide a theoretical basis for cultivating improved citrus rootstocks.

Reciprocal grafting between clones with contrasting drought tolerance suggests a key role of abscisic acid in coffee acclimation to drought stress

The role of abscisic acid (ABA) in drought tolerance of Coffea canephora is unknown. To determine whether ABA is associated with drought tolerance and if the use of tolerant rootstocks could increase ABA and drought tolerance, we performed reciprocal grafting experiments between clones with contrasting tolerance to drought (clone 109, sensitive; and clone 120, tolerant). Plants were grown in large (120 L) pots in a greenhouse and subjected to drought stress by withholding irrigation. The non-grafted 120 plants and graft treatments with 120 as a rootstock showed a slower reduction of predawn leaf water potential (Ψpd) and a lower negative carbon isotopic composition ratio compared with the other grafting combinations in response to drought. The same 120 graft treatments also showed higher leaf ABA concentrations, lower levels of electrolyte leakage, and lower activities of ascorbate peroxidase and catalase under moderate (Ψpd = − 1.0 or − 1.5 MPa) and severe (Ψpd = − 3.0 MPa) drought. Root ABA concentrations were higher in plants with the 120 rootstocks regardless of watering regime. The 120 shoots could also contribute to drought tolerance because treatment with 120/109 rootstock/scion combination showed postponed dehydration, higher leaf ABA concentration, and lower leaf electrolyte leakage compared with the sensitive clone. We conclude that both the shoot and root systems of the tolerant clone can increase the concentrations of ABA in leaves in response to drought. This further suggests that ABA is associated with a delayed onset of severe water deficit and decreased oxidative damage in C. canephora.

Breeding and screening persimmon rootstocks for saline stress tolerance

Soil and water salinity affect growth and cause physiological disorders in plants. Recently, the high level of salt accumulated in the soil has become a problem in the 'Ribera del Xuquer' area in Valencia. Diospyros lotus, the most common persimmon rootstock used in this area, is sensitive to salinity. Numerous studies have demonstrated that exclusion of Cl− and Na+ is under genetic control. Thus, selection of suitable genotypes would restrict the translocation of Cl− or Na+ to the grafted variety. To meet this goal, the 'Instituto Valenciano de Investigaciones Agrarias' (IVIA, Spain) started a persimmon rootstock breeding program focused on developing rootstock genotypes tolerant to salt stress. The rootstocks used for persimmon comprise three species: Diospyros kaki Thunb., D. lotus L. and D. virginiana L. The aim of our study was to test seedlings from these species for tolerance to salinity stress. The variables studied were chloride and sodium uptake, growth and leaf gas exchange parameters. Three-month-old plants were grown in a greenhouse and irrigated for 45 days with nutrient solutions differing in sodium chloride (NaCl) content (0, 30 and 50 mM). Plant water status was disrupted by salinity-induced osmotic stress. D. kaki and D. virginiana seedlings presented reduced leaf water content and stomatal conductance. After 60 days, the Cl− content was lowest in D. virginiana leaves and highest in D. lotus. Furthermore, the Na+ content was highly variable in D. lotus and D. kaki, but remained low in all D. virginiana genotypes. The leaf Ca2+ content was highly variable in all species. The Na+/Ca2+ ratio, an indicator of root selective permeability, showed high variability in D. kaki and D. lotus genotypes, but remained low in D. virginiana. Selection of D. lotus and D. kaki genotypes with low Cl− and Na+ contents could provide salt-tolerant persimmon rootstocks.

Polyethylene glycol damages grafted citrus plants based on biometric, physiological,and biochemical responses

Abstract Drought tolerance is a major trait for the selection of citrus rootstocks in breeding programs. PEG 4000 solution at 110 g L-1 (osmotic potential of -376 kPa) was used to evaluate biometric, physiological, and biochemical responses of grafted citrus plants in pots. ‘Valencia’ sweet orange plants grafted onto ‘Rangpur’ lime (drought tolerant) rootstock showed greater plant growth compared to that on ‘Swingle’ citrumelo (drought sensitive) rootstock, regardless of PEG-induced stress; however, biological responses to PEG were similar on both rootstocks. Plant dry weight, gas exchange, and leaf and root starch concentrations were reduced by PEG. Water potential at 2:00 p.m. and Fe and Mn leaf concentrations increased with severe phytotoxic symptoms. The results corroborate the limitation of PEG for assessing drought tolerance of citrus plants at the whole plant level.

Characterization of Citrus WRKY transcription factors and their responses to phytohormones and abiotic stresses

WRKY transcription factors (TF) family is involved in a huge variety of plant processes, including seed germination, plant development, phytohormone signalling, and defence against both biotic or abiotic stresses. In this work, WRKY TF family has been characterized in citrus. In a first experiment, the relative expression of CsWRKYs was analyzed in shoots and roots of plants treated with abscisic acid (ABA), salicylic acid (SA), and methyl jasmonate (MeJA) under in vitro conditions. Expression of CsWRKYs was also determined in roots of commercial citrus rootstocks subjected to osmotic and salt stresses. A total amount of 50 CsWRKYs has been found and devided into different groups of WRKY family according to the WRKY domain sequences. In response to the applications of phytohormones, the highest differences were observed in roots, and it was found that ABA and SA generally repressed CsWRKYs expressions, but MeJA induced their overexpression. Osmotic stress repressed the expression of most of the CsWRKYs, whereas salt stress induced their expression. Moreover, salt stress induced higher increase in CsWRKY expressions in the tolerant rootstock Citrus macrophylla than in the sensitive rootstock Carrizo citrange, suggesting that these TFs may play an important role in response to this stress.

Association of mineral imbalance with leaf chlorosis under saline irrigation in Sharad seedless grapes raised on Dog Ridge rootstock

Under saline irrigation, development of leaf chlorosis/discoloration beginning from the upper leaves has been found to cause severe reduction in productivity and life span of the Sharad Seedless grape (Vitis vinifera L.) and its mutants grafted on Dog Ridge rootstock. In the present study, mineral accumulation in vine tissues over the years under saline irrigation and association of mineral imbalance with chlorosis/necrosis was investigated during the two pruning seasons in Sharad Seedless vines grafted on Dog Ridge rootstock. The contents of nitrogen, phosphorus, potassium, calcium and magnesium were significantly lower and sodium and chloride contents were found significantly higher in upper leaf lamina of symptomatic vines. Lamina N, P, K and Ca and Mg contents were positively correlated, whereas sodium and chloride contents were negatively correlated with chlorophyll content. Significant negative correlation was observed between chloride and phosphorus and nitrogen concentration in leaf tissues. Principal component analysis revealed a negative interaction between N, P, K and Na and Cl−content in leaf tissues. Principal components (PCs) explained 91.7% of total variation in leaf lamina and were designated as PC1 (N+P+K-Na-Cl) and PC2 (N+P+K+Ca+Mg). Symptomatic vines accumulated higher sodium (>5.0 g−1/kg) than potassium content in the leaf tissues and mean potassium content in symptomatic leaf lamina was <5.0 g−1/kg. Increased accumulation of Na+ and Cl− in the chlorotic leaf tissues revealed that ability of Dog Ridge rootstock to exclude these salts diminished over time and long term studies are needed for identifying salt tolerant rootstocks.

Breeding tomato (Solanum lycopersicum L.) for resistance to biotic and abiotic stresses

Tomato (Solanum lycopersicum L.) is an important vegetable crop cultivated in the tropical and sub-tropical regions of the world. Low productivity in India is due to occurrence of both biotic and abiotic stresses. Among the biotic stresses, tomato leaf curl disease, bacterial wilt, early blight and Groundnut Bud Necrosis Virus disease have become serious production constraints causing considerable yield loss in the major tomato growing areas of the country. Adoption of multiple disease resistant varieties or F1 hybrids would be the most appropriate way to address these diseases. At ICAR-IIHR, Bengaluru systematic breeding strategies were employed to pyramid genes for resistance to early blight, bacterial wilt and tomato leaf curl diseases and to develop advanced breeding lines&amp; F1 hybrids with triple disease resistance. Stable source of resistance to early blight and bi-partite begomo-virus (Tomato Leaf Curl New Delhi Virus) has been identified in Solanum habrochaites LA-1777. Validation with molecular markers linked to tomato leaf curl virus resistance revealed that LA-1777 carryTy2 and other putative resistant genes. Several high yielding dual purpose hybrids were also developed for fresh market and processing with high level of resistance to multiple diseases. Cherry tomato lines have also been bred for high TSS, total carotenoids, total phenols, flavonoids, vitamin C, acidity and lycopene content. IIHR-249-1, IIHR-2101 (Solanum habrochaites LA-1777), IIHR- 2866 and IIHR-2864 recorded high values for quality parameters like total carotenoids, lycopene, vitamin C, total phenols, flavonoids and TSS. Drought tolerant root stock has been developed by an interspecific cross between S. habrochaites LA-1777 and S. lycopersicum (15 SB SB). Resistant sources have also been identified against Tuta absoluta, a serious insect pest reported from major tomato growing areas in the country in recent time. High temperature tolerant breeding lines are in pipe line.

Agronomic Management for Enhancing Plant Tolerance to Abiotic Stresses—Drought, Salinity, Hypoxia, and Lodging

Abiotic stresses are currently responsible for significant losses in quantity and reduction in quality of global crop productions. In consequence, resilience against such stresses is one of the key aims of farmers and is attained by adopting both suitable genotypes and management practices. This latter aspect was reviewed from an agronomic point of view, taking into account stresses due to drought, water excess, salinity, and lodging. For example, drought tolerance may be enhanced by using lower plant density, anticipating the sowing or transplant as much as possible, using grafting with tolerant rootstocks, and optimizing the control of weeds. Water excess or hypoxic conditions during winter and spring can be treated with nitrate fertilizers, which increase survival rate. Salinity stress of sensitive crops may be alleviated by maintaining water content close to the field capacity by frequent and low-volume irrigation. Lodging can be prevented by installing shelterbelts against dominant winds, adopting equilibrated nitrogen fertilization, choosing a suitable plant density, and optimizing the management of pests and biotic diseases harmful to the stability and mechanic resistance of stems and roots.

Functional differences in transport properties of natural HKT1;1 variants influence shoot Na+ exclusion in grapevine rootstocks.

Under salinity, Vitis spp. rootstocks can mediate salt (NaCl) exclusion from grafted V.vinifera scions enabling higher grapevine yields and production of superior wines with lower salt content. Until now, the genetic and mechanistic elements controlling sodium (Na+ ) exclusion in grapevine were unknown. Using a cross between two Vitis interspecific hybrid rootstocks, we mapped a dominant quantitative trait locus (QTL) associated with leaf Na+ exclusion (NaE) under salinity stress. The NaE locus encodes six high-affinity potassium transporters (HKT). Transcript profiling and functional characterization in heterologous systems identified VisHKT1;1 as the best candidate gene for controlling leaf Na+ exclusion. We characterized four proteins encoded by unique VisHKT1;1 alleles from the parents, and revealed that the dominant HKT variants exhibit greater Na+ conductance with less rectification than the recessive variants. Mutagenesis of VisHKT1;1 and TaHKT1.5-D from bread wheat, demonstrated that charged amino acid residues in the eighth predicted transmembrane domain of HKT proteins reduces inward Na+ conductance, and causes inward rectification of Na+ transport. The origin of the recessive VisHKT1;1 alleles was traced to V.champinii and V.rupestris. We propose that the genetic and functional data presented here will assist with breeding Na+ -tolerant grapevine rootstocks.

Salinity induced changes in water relations, oxidative damage and morpho-physiological adaptations of pistachio genotypes in soilless culture

Selecting salt tolerant rootstocks is a sustainable approach for developing fruit trees in salinity prone areas. 60-day-old seedlings of Pistacia vera ‘Akbari’ and ‘Ghazvini’, and P. vera ‘Ghazvini’ × P. atlantica (G×A) were subjected to 0, 50, 100 and 150 mM NaCl in half strength Hoagland’s nutrient solution. After 45 days, the growth, water relations, and oxidative damage parameters were investigated. Salt stress reduced plant biomass, height, crown diameter and leaf number, but increased specific leaf area (SLA) of the seedlings. Under salt stress, the growth of ‘Akbari’ seedlings was higher than the other genotypes. Accumulation of malondialdehyde (MDA) and proline was observed in the leaves of salt affected seedlings. ‘Ghazvini’ seedlings had the highest MDA concentration and the lowest cell membrane stability in their leaves. Degredation of photosynthetic pigments under salt stress was lower in the leaves of ‘Akbari’ seedlings than that in other genotypes. Increase in leaf succulence was observed in ‘Akbari’ and G×A seedlings in response to salt stress. Relative water content and concentration of anthocyanins in the leaves of pistachio genotypes remained unchanged under salt stress. The results revealed that monitoring leaf abscission, SLA, leaf succulence, MDA concentration, and photosynthetic pigments provide suitable contrast for screening salt tolerance in pistachio. Furthuremore, ‘Akbari’ was found to be the most salt tolerant genotype.

Grafting pepper onto tolerant rootstocks: An environmental-friendly technique overcome water and salt stress

Abstract Salinity and water shortages are two of the biggest environmental constraints that crops have to face in the climate change scenario. A fast and efficient way to overcome these stresses under the prism of a sustainable crop management is the use of grafting, combining the desired cultivar with the rootstock providing tolerances to abiotic stresses. Our aim was to validate three accessions previously selected for their tolerances to salt and water stresses (A25, B14 and C12) as rootstocks, in real field conditions. The physiological and productive behavior of the commercial pepper ‘Adige’ (A) grafted onto these accessions was compared along the growing cycle with this cultivar grafted onto the commercial rootstock ‘Antinema’ (ANT) and with the ungrafted pepper plant (A). Under water and salt stress, grafted plants onto the selected accessions, gave higher marketable yields than ungrafted plants or that plants grafted onto ANT, particularly the A25 accession. This rootstock was able to maintain high photosynthesis levels under stressing conditions through different adjustments made in the physiological processes, such as proline accumulation. The ANT rootstock showed comparable yields to A25 in control conditions. Under salt stress, Na + and Cl − were equally accumulated in A/A25 plants and the ungrafted ones, but A/ANT, A/B14 and A/C12 were more restrictive in their absorption along the growing season. These results reinforce the idea that the use of tolerant pepper rootstocks is a good adaptation strategy for abiotic stressing conditions. The results also suggest that the abiotic stress was alleviated by the lack of negative effects mainly on photosynthesis, which maintained plant growth and the marketable yield.