Root Sugar Content Research Articles

Effect of salinity on sodium and chloride uptake, proline and soluble carbohydrate contents in three alfalfa varieties

Salinity stress affected severely plant growth and production. Indeed, soil salinity represented one of the most important environmental stresses, which caused serious threats to agriculture and also results in the deterioration of environment. Accumulation of sodium, chloride, proline and soluble sugars was investigated in leaves, stems and roots of three alfalfa varieties (Hunterfield, Hyb.555 and Gabes) at the late bloom-early pod stage. The study was conducted in a greenhouse for 90 days of salt stress in whole-plants. Plants were irrigated with top water with four NaCl concentrations: (0 - 2.5 - 5 and 10g.l -1 ). Results showed that all varieties accumulated high Na + and Cl - contents in leaves and stems. Gabes variety differed from Hunterfield and Hyb.555 with Na + and Cl - contents significantly lower in leaves at the stressful treatments. Furthermore, Gabes proline content at 5 and 10g.l -1 NaCl in three organs was significantly higher than in the introduced varieties. Proline content in leaves, stems and roots increased with the rise of salt in pots, reaching a significantly higher level for Gabes at the stressful treatment (10g.l -1 ). Soluble sugar content in leaf tissue was higher in Gabes than those in the introduced varieties at the stressful treatments (5 and 10g.l -1 ). Contrary to the air parts (leaves and stems), soluble sugar contents in roots for Hunterfield and Hyb.555 are significantly higher, compared to Gabes variety, at the stressful treatment. This could be probably related to the difficulty in generating new leaves in Hunterfield and Hyb.555 varieties. Keyword: Alfalfa; chloride; proline; Salinity; sodium; soluble carbohydrate.

Influence of combined herbicide protection and microelements fertilization to yield parameters of sugar beet rootsWpływ łączenia ochrony herbicydowej oraz dokarmiania mikroelementami na jakość plonu korzeni buraka cukrowego

Summary The aim of investigation was to evaluate the effect of combined application of herbicides with microelements fertilization on the yield parameters of sugar beet roots. The combined application of herbicides with fertilizers on allows to save outlays, but may have a negative influence on the growth, development, yielding and qualitative parameters of sugar beet. The results of conducted trials indicated that combined herbicide protection and microelements fertilization did not significantly differentiate the yield parameters of sugar beet roots. The level of sugar content in roots was only slightly differentiated under the influence of the joint application of herbicide protection and microelements fertilization. No significant differentiation of sodium, potassium and α-amonium nitrogen content was stated under the influence of joint or separate application of herbicide protection and microelements fertilization.

Effect of salinity and seed priming on growth and biochemical parameters of different barely genotypes

An experiment was conducted to investigate the interactive effect of salinity and seed priming on barely genotypes at the Institute of Biotechnology and Genetic Engineering (IBGE), Khyber Pakhtun Khwa Agricultural University Peshawar Pakistan. The experiment was carried out in completely randomized design (CRD) with three replications consisting of twelve barely genotypes (Haider-93, Soorab-96, Arabic Asward, NRB-37, Frontier-87, Jau-83, Balochistan-Local, NRB-31, KPK-Local, Sanober-96, Awarn-2002 and AZ-2006) at two seed conditions (seed priming with 30 mM NaCl or no seed priming) under four salinity levels (0, 50, 100 and 150 mM). The results revealed that seed priming and salinity had significantly (p≤0.05) affected all the parameters under study. However, the effect of seed priming was non significant (p>0.05) on shoot chlorophyll a content (mg g -1 fresh weight) and root sugar content (mg g -1 dry weight). Salinity stress had adversely affected growth and biochemical parameters of barley genotypes, however, seed priming with NaCl had diminished the negative impact of salt stress. Maximum shoot dry weight plant -1 (1.81 g), root dry weight plant -1 (0.42 g), shoot K + content (1.41 mg g -1 dry weight), root sugar content (7.55 mg g -1 dry weight) were recorded in Balochistan-Local. Similarly, Haider-93 produced highest root K + content (0.67 mg g -1 dry weight), shoot sugar content (16.36 mg g -1 dry weight), shoot chlorophyll a content (3.44 mg g -1 fresh weight) and shoot chlorophyll b content (1.78 mg g -1 fresh weight). Maximum shoot Na + content (1.20 mg g -1 ) and root Na + content (1.47 mg g -1 ) was recorded in Frontier-87. Seed priming had significantly (P<0.05) enhanced all the aforementioned parameters. The positive effect of seed priming was more profound in Balochistan-Local followed by Haider-93 as compared to other genotypes. Key words : Barely, salinity, seed priming, Na + , K + , chlorophyll a and b.

Responses of five woody species to burial by marly sediment: the role of biomass allocation pattern flexibility

In eroded lands of the French Southern Alps, burial of early established seedlings under marly sediment weakens the effect of vegetation on soil stabilization and sediment trapping. Therefore, this protective role is largely dependent on species' resistance to burial, and the understanding of species' tolerance to this environmental disturbance is highly valuable for basic knowledge on plant succession and for ecological restoration purposes. The response of five woody species with contrasting ecological requirements and natural habitats—three tree species, Pinus nigra, Robinia pseudoacacia and Acer campestre, and two shrubs, Ononis fruticosa and Hippophae rhamnoides—to experimental burial under marly sediment was studied. Seedlings were exposed to three burial levels: no burial (control), partial burial (50% of seedling height) and complete burial (100% of seedling height). Burial tolerance was evaluated based on seedling survival, height and biomass. Biomass allocation to shoots and roots and soluble sugar and starch contents in roots and stems were measured to identify plant traits that determine species response to burial. All species survived partial burial but only A. campestre seedlings emerged from complete burial. Tree species were more tolerant to burial and buried plants showed no significant differences with control. The two shrubs were found less tolerant and buried plants showed slower growth than controls. The results showed that species response was not related to initial soluble and starch content in roots and stems, but instead to biomass allocation pattern flexibility.

Genetic diversity of sugar beet parents and hybrids grown in rhizomania conditions

In this study, properties and level of resistance of genetically sugar beet genotypes of parents and hybrids growing in field infested with rhizomania are estimated. For this investigation, we used 14 tetraploids multigerm genotypes-pollinators (Rh1- Rh14 4n MM) and 6 maternal lines, 2n mm MS, (diploid monogerm, male sterile lines with their sterile analog): 2MS, 7MS, 5MS, 1MS, 3MS, and 4MS. Also, hybrids, achieved by conventional breeding using the aforementioned parent components, were used for investigation of their reaction to soil infested by rhizomania in a different location. In this study, variability of root of yield and sugar content in parents and hybrids grown on experimental field infested by rhizomania were analyzed. Different values of root yield and sugar content within parent cultivars and hybrids of sugar beet were established, depending on the level of resistance/tolerance to rhizomania. The susceptibility of genotype yield of root and content of sugar was highly significantly lower than the tolerance of genotypes of sugar beet. Key words: Sugar beet, rhizomania, root yield, content of sugar, resistance.

Salt stress induced ion accumulation, ion homeostasis, membrane injury and sugar contents in salt-sensitive rice (Oryza sativa L. spp. indica) roots under iso- osmotic conditions

Excess salt induced ionic and osmotic stresses that disturbed metabolism and led to reduction of plant development. Previous studies reported that sugars in stressed plants were involved in stress tolerance. However, the role of sugars in salt-stressed plants against only ionic effects is still unclear. The objective of this research was to investigate accumulation and homeostasis of ions, membrane injury, water content, growth characters and sugar contents in roots, in-response to salt stress under iso-osmotic conditions. Salt-sensitive rice, Pathumthani1 (PT1) was grown on MS culture medium for 7 days and was adjusted to salt stress under iso-osmotic conditions (-1.75 ± 0.20 MPa) by mannitol for 4 days. An increase in NaCl increased Na + and Na + :K + in PT1 roots leading to increased membrane injury, while the water content was decreased. Additionally, growth characters, including number, length, fresh weight and dry weight of roots, were inhibited. Sugar accumulations in PT1 roots were enhanced by increases in NaCl. The increase in Na+ was positively related to total soluble sugars, resulting in an osmotic adjustment of the membrane that maintained water availability. The accumulation of sugars in PT1 roots may be a primary salt-defense mechanism and may function as an osmotic control. Key words: Mannitol, membrane injury, oligosaccharides, sodium ion, potassium ion, sodium chloride.

Effect of salinity and seed priming on growth and biochemical parameters of different barely genotypes

An experiment was conducted to investigate the interactive effect of salinity and seed priming on barely genotypes at the Institute of Biotechnology and Genetic Engineering (IBGE), Khyber Pakhtun Khwa Agricultural University Peshawar Pakistan. The experiment was carried out in completely randomized design (CRD) with three replications consisting of twelve barely genotypes (Haider-93, Soorab-96, Arabic Asward, NRB-37, Frontier-87, Jau-83, Balochistan-Local, NRB-31, KPK-Local, Sanober-96, Awarn-2002 and AZ-2006) at two seed conditions (seed priming with 30 mM NaCl or no seed priming) under four salinity levels (0, 50, 100 and 150 mM). The results revealed that seed priming and salinity had significantly (p≤0.05) affected all the parameters under study. However, the effect of seed priming was non significant (p>0.05) on shoot chlorophyll a content (mg g -1 fresh weight) and root sugar content (mg g -1 dry weight). Salinity stress had adversely affected growth and biochemical parameters of barley genotypes, however, seed priming with NaCl had diminished the negative impact of salt stress. Maximum shoot dry weight plant -1 (1.81 g), root dry weight plant -1 (0.42 g), shoot K + content (1.41 mg g -1 dry weight), root sugar content (7.55 mg g -1 dry weight) were recorded in Balochistan-Local. Similarly, Haider-93 produced highest root K + content (0.67 mg g -1 dry weight), shoot sugar content (16.36 mg g -1 dry weight), shoot chlorophyll a content (3.44 mg g -1 fresh weight) and shoot chlorophyll b content (1.78 mg g -1 fresh weight). Maximum shoot Na + content (1.20 mg g -1 ) and root Na + content (1.47 mg g -1 ) was recorded in Frontier-87. Seed priming had significantly (P<0.05) enhanced all the aforementioned parameters. The positive effect of seed priming was more profound in Balochistan-Local followed by Haider-93 as compared to other genotypes. Key words : Barely, salinity, seed priming, Na + , K + , chlorophyll a and b.

Low Magnesium with High Potassium Supply Changes Sugar Partitioning and Root Growth Pattern Prior to Visible Magnesium Deficiency in Leaves of Rice (&amp;lt;i&amp;gt;Oryza sativa&amp;lt;/i&amp;gt; L.)

This research was conducted to investigate the effects of low magnesium (Mg) with high potassium (K) supply on the Mg concentration, sugar partitioning and root growth of rice (Oryza sativa L. cv. Wuyunjing 7) plants grown in hydroponics under greenhouse conditions, at Nanjing Agricultural University, China. The nutrient solution contained 0.01 and 1.0 mM Mg concentration, with K at 1.0 and 6.0 mM. Compared with the control (1mM Mg and K) treatment, the soluble sugar content at the treatment of low Mg (0.01 mM) with high K (6 mM) decreased by 35.7% in leaves, whereas increased 29.2% in roots at day 15 after treatment initiation. The shoot dry weight (DW) declined 12.9%, but root DW increased 12.1% leading to the significant increase in the root to shoot ratio at day 30. Furthermore, the total root length, total root surface area, root volume, average root diameter, total length of 0 - 0.5 mm and 0.5 - 1.0 mm diameter roots at day 30 significantly increased by 11.8%, 16.4%, 25.3%, 8.1%, 16.6% and 12.5%, respectively. Correlation analysis revealed the root to shoot ratio is closely related to the soluble sugar contents in roots and root morphological parameters of rice at day 15 and day 30. The typical visible symptoms of Mg deficiency in leaves of rice were obtained in the treatment of low Mg with high K at day 35. These findings indicated that low Mg with high K supply altered sugar partitioning and root morphological parameters, resulting in the increased root to shoot ratio prior to visible Mg deficiency symptoms in rice leaves. The increase in root to shoot ratio maybe an important adaptive mecha-nism for rice plants to respond to low-Mg stress during the early growth stage.

Submergence tolerance in Hordeum marinum: dissolved CO2 determines underwater photosynthesis and growth

Floodwaters differ markedly in dissolved CO2, yet the effects of CO2 on submergence responses of terrestrial plants have rarely been examined. The influence of dissolved CO2 on underwater photosynthesis and growth was evaluated for three accessions of the wetland plant Hordeum marinum Huds. All three accessions tolerated complete submergence, but only when in CO2 enriched floodwater. Plants submerged for 7 days in water at air equilibrium (18 µM CO2) suffered loss of biomass, whereas those with 200 µM CO2 continued to grow. Higher underwater net photosynthesis at 200 µM CO2 increased by 2.7- to 3.2-fold sugar concentrations in roots of submerged plants, compared with at air equilibrium CO2. Leaf gas films enhancing gas exchange with floodwater, lack of a shoot elongation response conserving tissue sugars and high tissue porosity (24–31% in roots) facilitating internal O2 movement, would all contribute to submergence tolerance in H. marinum. The present study demonstrates that dissolved CO2 levels can determine submergence tolerance of terrestrial plants. So, submergence experiments should be conducted with defined CO2 concentrations and enrichment might be needed to simulate natural environments and, thus, provide relevant plant responses.

Exogenous polyamines affect mycorrhizal development of Glomus mosseae-colonized citrus (Citrus tangerine) seedlings.

To increase mycorrhizal colonization of citrus, exogenous polyamines (PAs) including putrescine (Put), spermidine (Spd), and spermine (Spm) were applied to three-month-old Glomus mosseae-colonized Citrus tangerine seedlings. Three months after the application of PAs, all the seedlings increased mycorrhizal colonization and entry points, Put and Spm treatments significantly increased the number of arbuscules, and Spd and Put treatments notably increased the number of vesicles. Applications of exogenous Put and Spd, but not Spm, markedly increased shoot and root dry weights of the mycorrhizal seedlings. PAs significantly increased leaf glucose content of mycorrhizal seedlings, and Put and Spd treatments markedly increased leaf sucrose content of mycorrhizal seedlings. Spm treatment significantly reduced root sucrose content of mycorrhizal seedlings, and only Put treatment significantly increased root glucose content of mycorrhizal seedlings. Compared to the sole mycorrhizal inoculation, exogenous PAs significantly reduced allocation of sucrose to root, and additional Spd significantly decreased allocation of glucose to root. The results demonstrated that exogenous PAs applications could improve mycorrhizal development of citrus seedlings, possibly due to changes of leaf and root sugar content.

Influence of arbuscular mycorrhiza on lipid peroxidation and antioxidant enzyme activity of maize plants under temperature stress

The influence of the arbuscular mycorrhizal (AM) fungus, Glomus etunicatum, on characteristics of growth, membrane lipid peroxidation, osmotic adjustment, and activity of antioxidant enzymes in leaves and roots of maize (Zea mays L.) plants was studied in pot culture under temperature stress. The maize plants were placed in a sand and soil mixture under normal temperature for 6 weeks and then exposed to five different temperature treatments (5 degrees C, 15 degrees C, 25 degrees C, 35 degrees C, and 40 degrees C) for 1 week. AM symbiosis decreased membrane relative permeability and malondialdehyde content in leaves and roots. The contents of soluble sugar content and proline in roots were higher, but leaf proline content was lower in mycorrhizal than nonmycorrhizal plants. AM colonization increased the activities of superoxide dismutase, catalase, and peroxidase in leaves and roots. The results indicate that the AM fungus is capable of alleviating the damage caused by temperature stress on maize plants by reducing membrane lipid peroxidation and membrane permeability and increasing the accumulation of osmotic adjustment compounds and antioxidant enzyme activity. Consequently, arbuscular mycorrhiza formation highly enhanced the extreme temperature tolerance of maize plant, which increased host biomass and promoted plant growth.

Lead stress in seedlings of Avicennia marina, a common mangrove species in South China, with and without cotyledons

The effects of lead (Pb; 0–1000 mg L −1) stress on the growth and biochemical responses of seedlings of Avicennia marina were examined, with and without cotyledons. After 50 days exposure to Pb, the growth of A. marina was not affected at low concentrations (0–50 mg L −1 Pb). Roots tolerated to high Pb concentrations, with a significant reduction in biomass only at 1000 mg L −1 Pb. In leaves and stems, 500 mg L −1 Pb already caused a significant decline in biomass (0.6-fold). Accumulation of Pb occurred mainly in roots, with some accumulation in cotyledons but very little in leaves. Pb concentrations in both roots and cotyledons were proportional to the Pb levels in the substrate ( y = 25.945 x − 4281, r 2 = 0.67, P = 0.001 for roots, and y = 0.249 x + 45.636, r 2 = 0.879, P < 0.001 for leaves). In treatments with 500 and 1000 mg L −1 Pb, nitrogen concentrations in cotyledons were higher, while the carbon to nitrogen ratios were significantly lower than in the control without Pb. The Pb levels had significant positive effects on sugar content, MDA concentration and POD activity in both roots and leaves, while the removal of cotyledons significantly decreased the POD activity and MDA content in roots A. marina seedlings according to the two-way multivariate analysis of variance test. The sugar content in the cotyledon of Pb-treated seedlings was significantly lower than that in the control (without Pb), suggesting that more carbohydrate reserves (e.g., sugar) stored in cotyledons had been mobilized to leaves and even roots under Pb treatment.

The use of Vis/NIR spectroscopy to predict the optimal root harvesting date of chicory ( Cichorium intybus L.)

The use of Visible/Near Infrared (Vis/NIR) spectroscopy has been evaluated to determine the optimal harvesting date of chicory roots. Indirect maturity parameters, such as the foliage chlorophyll content, root dry matter, sugar and nitrogen content, were measured for two hybrids during the field growing season. The root harvest date, which resulted in the highest percentage of top quality chicory heads after forcing, was chosen as the optimal harvest date. A principal component analysis indicated the presence of both a time and hybrid effect. Partial least square models were constructed to predict the indirect maturity parameters and the number of days before optimal root harvest. Correlations for cross validation between 0.75 and 0.81 were obtained for the prediction of foliage chlorophyll content. For the first time, leaf spectra were used to predict chicory root characteristics with success: root dry matter percentage had a cross validation correlation of 0.81 for the ‘Mont Blanc’ and 0.88 for the ‘Vintor’ hybrids. The prediction of root sugar and nitrogen content was poor (cross validation correlation of 0.62 and 0.74). Predicting the number of days before optimal root harvest was done reasonably accurately, with prediction errors of 8.86 d and 10.61 d for ‘Mont Blanc’ and ‘Vintor’, respectively. The visual part of the spectrum is not required in these calibration models. Data of more years and hybrids should be taken into account to make the models more robust and applicable for farmer practice.

Seasonal growth dynamics of Siberian spruce ectomycorrhiza and sugar content in it

Seasonal growth, dynamics of morphological and anatomical structure, and sugar content in ectomycorrhizal roots of Siberian spruce (Picea obovata Ledeb.) were studied. A variability of the root tip structure related to variations in hydrothermal conditions in soils of spruce phytocenoses was observed. A high content of mono- and disaccharides was detected in root tips in the beginning and end of the growth season. Changes in the growth pattern of spruce mycorrhizal roots were associated with changes in the sugar concentration in them, the thickness and volume of the mycelium sheath, and respiration.

Browsed Betula pubescens trees are not carbon‐limited

Summary 1Slower growth after repetitive browsing of young trees has been attributed to a carbon (C) limitation, but data from long-term studies are lacking. To determine if repeated summer browsing causes a C (source) limitation in trees in the long-term, we analysed the non-structural carbohydrate (NSC) and nitrogen (N) concentrations and pools of Betula pubescens saplings subjected to different clipping treatments (unclipped, 33% and 66% shoot removal) for 7 years. 2The short-term effect of browsing on C allocation was assessed by clipping trees with different browsing histories and analyzing their C and N responses within the same growing season. 3Long-term repetitive summer browsing significantly decreased sapling growth and soluble sugar (SS) concentrations in fine roots. However, trees subjected to different browsing histories did not change their C partitioning into starch. Although trees with a different browsing history showed differences in the NSC concentrations and pools of leaves, these differences were not maintained through time. 4Simulated browsing had no significant short-term effect on root C and N pools of birch trees, but it decreased all C pools in leaves, 1-year and current-year stems and the starch and total NSC pools in main stems. 5We conclude that although browsing may cause a temporary decrease in C pools, B. pubescens trees are able to compensate for such losses and hence are not C-limited in the long-term.

RESPONSE OF SOME SWEET POTATO GENOTYPES TO A SLOW- RE-LEASE NITROGEN FERTILIZER UNDER ASSIUT CONDITIONS

This work was carried out during the two sum-mer seasons of 2006 and 2007 at Arab El-Awammer Research Station (A.R.C.); Assiut, Egypt, to study the effect of Enciabien as a slow- release fertilizer on sweet potato plants grown in newly reclaimed soil. Three genotypes of sweet potato ( two clones Assiut 201, 202 and one culti-var 17/8) and four levels of nitrogen i;e. 20 N units of ammonium sulphate (control ), 20 N units , 40 N units and 60 N units of Enciabien were used in the present study. The results indicated that applying 60 N units of Enciabien gave the best result in most of studied characters. Also, genotype Assiut 201 was the best genotype under the experiment condition for the most studied characters. The in-teraction between 60 N unit of Enciabien and culti-var 17/8 gave the highest averages of vine weight, main stem length and highest number of branch-es/plant, while the interaction between 40 N units of Enciabien and Assiut 201 gave the best number of marketable storage roots/plant, weight of mar-ketable storage roots/plant, total yield/fed and av-erage of root diameter. High dry matter content and high starch root percentage were obtained from genotype Assiut 201 when received any of four tested nitrogen levels. While, high percentage of fiber in sweet potato roots were obtained from the interaction between Assiut 202 and all levels of nitrogen. The highest percentage of sugar content in sweet potato roots was obtained from cultivar 17/8 when received any of four used N levels.

Dynamics of Soluble Sugar and ABA Contents in Leaves and Roots of Catharanthus roseus Seedlings Subjected to Natural Drought Condition

Slow rate of water loss(RWL) in leaf surface is induced by removal of plants from soil,leading to drought stress to some extent.In the present paper,Catharanthus roseus with strong desiccation tolerance was conducted to investigate the dynamics of ABA and soluble sugar contents in leaves and roots.The ABA content in roots of seedlings was lower than that in leaves in control condition,while dehydration treatment promoted its accumulation in roots,arriving at the peak value at 6h.The activity of acid invertase(AI) may be activated by elevated ABA and increased by 30% after 6h treatment.Total soluble sugar content in control leaves was observed to be very stable,but when exerted in stress,they appeared to increase linear with prolong of stress time(r2=0.964).At the same time,sucrose and hexose also exhibited the trend of enhancement due to drought stress,to play a role of osmotic adjustment.

Ring nematodes ( Mesocriconema xenoplax) alter root colonization and function of arbuscular mycorrhizal fungi in grape roots in a low P soil

A reduction of arbuscules in roots of grapevines ( Vitis vinifera) observed when ring nematodes were added to field microplots led to the hypothesis that nematode feeding suppresses arbuscules by competing for root carbohydrates. Support for this hypothesis was tested by growing ‘Pinot noir’ grapevines in a factorial experiment with three levels of initial nematode densities (0, 0.1, 1.0 nematodes g −1 soil), two levels of light (full sun, 50% sun), and two levels of AMF (nonAMF, +AMF). Effects on plant growth were primarily driven by a light and AMF treatment interaction, such that low light increased stem dry matter accumulation at the expense of roots in +AMF vines only. Nematodes had only a minor influence on plant growth (leaf mass was reduced at the highest nematode density), but nematodes did not affect overall plant dry matter accumulation. Since nonAMF vines were severely limited by P and their growth was so poor, the impact of nematode and light treatments was further analyzed in +AMF plants only. Nematode populations, AMF colonization, and root carbohydrates were differentially affected by initial nematode density or light levels. Root biomass, and reducing sugar and starch concentrations in fine roots were reduced by low light, but the final nematode populations and arbuscule frequencies in roots were unaffected by light. Nematodes reduced arbuscules and starch concentrations in fine roots, but did not affect total colonization by AMF (hyphae, vesicles or arbuscules). Nematodes reduced plant P and K uptake at the highest density, and low light reduced Mg uptake. These findings are consistent with the hypothesis that ring nematodes suppress arbuscules in roots via competition for root carbohydrates. However, the lack of a treatment interaction between light and nematodes in our study suggests that ring nematode–AMF interactions in grape roots are controlled by more than competition for photosynthate.

Natural DNA variation at candidate loci is associated with potato chip color, tuber starch content, yield and starch yield

Complex characters of plants such as starch and sugar content of seeds, fruits, tubers and roots are controlled by multiple genetic and environmental factors. Understanding their molecular basis will facilitate diagnosis and combination of superior alleles in crop improvement programs (“precision breeding”). Association genetics based on candidate genes is one approach toward this goal. Tetraploid potato varieties and breeding clones related by descent were evaluated for 2 years for chip quality before and after cold storage, tuber starch content, yield and starch yield. Chip quality is inversely correlated with tuber sugar content. A total of 36 loci on 11 potato chromosomes were evaluated for natural DNA variation in 243 individuals. These loci included microsatellites and genes coding for enzymes that function in carbohydrate metabolism or transport (candidate loci). The markers were used to analyze population structure and were tested for association with the tuber quality traits. Highly significant and robust associations of markers with 1–4 traits were identified. Most frequent were associations with chip quality and tuber starch content. Alleles increasing tuber starch content improved chip quality and vice versa. With two exceptions, the most significant and robust associations (q < 0.01) were observed with DNA variants in genes encoding enzymes that function in starch and sugar metabolism or transport. Comparing linkage and linkage disequilibrium between loci provided evidence for the existence of large haplotype blocks in the breeding materials analyzed.Electronic supplementary materialThe online version of this article (doi:10.1007/s00122-008-0746-y) contains supplementary material, which is available to authorized users.

Changes in physiological indicators associated with salt tolerance in two contrasting cashew rootstocks

In order to identify salt tolerance indicators, several physiological variables were evaluated in two contrasting cashew (Anacardium occidentale L.) rootstocks in response to salt stress. The tolerant CCP 09 genotype showed better growth performance after two weeks under a large range of NaCl salinity (50, 100, 150 and 200 mM). The NaCl treatments induced a significant drop in transpiration as a consequence of an increased stomatal resistance in both genotypes. No significant differences in Na+, Cl, and K+ concentrations were found in both roots and leaves regardless of rootstocks. The tolerant genotype exhibited lower relative water content and less negative leaf osmotic potential as compared with the sensitive genotype and, therefore, these variables could not be related to salt tolerance. Salt stress caused more significant changes in protein and amino acid concentrations in roots than in leaves. Among the physiological indicators, leaf membrane damage was closely associated with the differences in salt tolerance between the two cashew genotypes. Furthermore, under NaCl salinity the tolerant rootstock showed greater ability to accumulate compatible organic solutes (amino acids, proline and soluble sugars) in leaves in addition to maintaining the soluble sugar concentration in roots as compared with the sensitive rootstock.