Morpho-physiological responses of sugar beet (Beta vulgaris L.) genotypes to drought stress

The identification of morpho-physiological traits related to drought tolerance and high yield potential is a challenge when selecting sugar beet genotypes with greater tolerance to water stress. In this paper, root morphological parameters, antioxidant systems, leaf relative water content (RWC) and H⁺-ATPase activity as key morpho-physiological traits involved in drought tolerance/susceptibility of sugar beet were studied. Genotypes showing a different drought tolerance index (DTI) but a similar yield potential, under moderate (?0.6 Mpa) and severe (?1.2 MPa) water stress, were selected and their morpho-physiological traits were investigated. The results showed a wide genetic variation in morpho-physiological parameters which demonstrated the different adaptive strategies under moderate and severe drought conditions in sugar beet. In particular, an efficient antioxidant system and redox signalling made some sugar beet genotypes more tolerant to drought stress. The alternative strategy of other genotypes was the reduction of root tissue density, which produced a less dense root system improving the axial hydraulic conductivity. These results could be considered as interesting challenge for a better understanding of the drought tolerance mechanisms in sugar beet.     

A Rootstock Provides Water Conservation for a Grafted Commercial Tomato (Solanum lycopersicum L.) Line in Response to Mild-Drought Conditions: A Focus on Vegetative Growth and Photosynthetic Parameters

The development of water stress resistant lines of commercial tomato by breeding or genetic engineering is possible, but will take considerable time before commercial varieties are available for production. However, grafting commercial tomato lines on drought resistant rootstock may produce drought tolerant commercial tomato lines much more rapidly. Due to changing climates and the need for commercial production of vegetables in low quality fields there is an urgent need for stress tolerant commercial lines of vegetables such as tomato. In previous observations we identified a scion root stock combination (‘BHN 602’ scion grafted onto ‘Jjak Kkung’ rootstock hereafter identified as 602/Jjak) that had a qualitative drought-tolerance phenotype when compared to the non-grafted line. Based on this initial observation, we studied photosynthesis and vegetative above-ground growth during mild-drought for the 602/Jjak compared with another scion-rootstock combination (‘BHN 602’ scion grafted onto ‘Cheong Gang’ rootstock hereafter identified as 602/Cheong) and a non-grafted control. Overall above ground vegetative growth was significantly lower for 602/Jjak in comparison to the other plant lines. Moreover, water potential reduction in response to mild drought was significantly less for 602/Jjak, yet stomatal conductance of all plant-lines were equally inhibited by mild-drought. Light saturated photosynthesis of 602/Jjak was less affected by low water potential than the other two lines as was the % reduction in mesophyll conductance. Therefore, the Jjak Kkung rootstock caused aboveground growth reduction, water conservation and increased photosynthetic tolerance of mild drought. These data show that different rootstocks can change the photosynthetic responses to drought of a high yielding, commercial tomato line. Also, this rapid discovery of one scion-rootstock combination that provided mild-drought tolerance suggests that screening more scion-rootstock combination for stress tolerance may rapidly yield commercially viable, stress tolerant lines of tomato.     

Effects of beet cryptic virus infection on sugar beet in field trials

The effects of beet cryptic virus (BCV) infection on sugar beet crops were investigated in field trials in 1990. Two sugar beet breeding stock lines were screened for infection by BCV. Seed lots containing different proportions of seed infected with BCV1 & 2 were obtained by crossing the stock lines and used in field trials at five different sites. Five characteristics of the infected plants were assessed. BCV infection appeared to have no significant effects on the sugar beet crop at four locations which suffered from drought stress but significant effects were found at one site where the crop was grown on grade 1 land with good moisture retention properties. Root yield and sugar yield were reduced by up to 17% and 20%, respectively, by BCV infection.     

超表达AVP1基因提高甜菜的耐低磷和耐盐抗旱性

为探讨H⁺-焦磷酸酶编码基因对甜菜磷吸收和抗性的影响，实现优良基因在甜菜基因工程中的利用，研究在甜菜中超表达拟南芥液泡膜H⁺-焦磷酸酶编码基因AVP1,对转基因甜菜分析其耐低磷、耐盐性和抗旱性。结果显示，AVP1基因在甜菜植株的叶片和块根中表达，且在逆境胁迫下增强表达量响应胁迫；低磷处理条件下，转基因甜菜与野生型甜菜相比具有更高的含磷量，可提高甜菜对磷的吸收利用效率；干旱、盐胁迫处理条件下，AVP1基因在转基因甜菜中显著上升，在盐胁迫或干旱处理条件下，转基因植株的生长受抑程度相对较轻。随着盐和干旱胁迫的加剧，转基因植株体内MDA含量与野生型植株相比较低而脯氨酸含量显著增加，AVP1基因可通过减轻逆境对甜菜细胞膜的损伤及提高甜菜细胞的渗透调节能力，进而增强甜菜对高盐和干旱胁迫的抗性。     

Inherited resistance of sugar beet to aphid colonization

Results of glasshouse experiments have confirmed that inbred lines of sugar beet differ in each of three types of resistance to Myzus persicae Sulz. and Aphis fabae Scop., namely: resistance to settling, resistance to multiplication, and tolerance. Resistance to multiplication was not invariably associated with resistance to settling, although plants of some lines showed both forms of resistance. Plants that were resistant to settling of alatae were not always resistant to apterae of the same species, and there was not a close relationship between resistance to M. persicae and to A. fabae. The mechanisms involved in resistance to aphids in sugar beet are not understood. Progenies of plants, selected for resistance to aphids from inbred lines, were often more resistant than progenies of unselected plants. Inheritance of each type of resistance is probably polygenic. The potential value of the different kinds of resistance, in reducing direct feeding damage and controlling the spread of virus yellows in the field, is discussed. The ultimate breeding objective is to produce commercial varieties in which appropriate kinds of resistance to aphids are combined with resistance to virus yellows. The use of such varieties would reduce the need to control aphids in the field by applications of chemicals.     

An analysis of the variation in crown size in sugar-beet (Beta vulgaris) grown in England

The processed part of the sugar-beet plant, the beet, consists of secondary storage tissues developed from the root and hypocotyl and the crown which, botanically, is the compressed stem. Crowns contain less sugar than roots and higher concentrations of melassigenic substances (such as amino-nitrogen compounds, sodium, potassium and invert sugars) which impair the crystallisation of white sugar during processing and make beets with high proportions of crown costly to process. Two factors influence the amount of crown material in beet delivered to factories: the original size of the whole crown in intact beet (subsequently referred to as the biological crown), and the fraction removed by the topping mechanisms of beet harvesters when the crop is lifted. The residue left on the delivered beet, for which growers in the UK are not paid, is measured as crown tare at the factory. To understand the causes of variation in crown tare, an analysis was made of the trend and variation in the size of the biological crown of sugar beet varieties introduced in the UK during the last 25 yr using information from past variety trials and new trials done in 1993, 1997 and 1998. Except for a few diploids, the biological crown was generally as large and variable in recently-introduced varieties as in those grown 15–20 yr ago. Its size was strongly influenced by locational and seasonal factors which changed the plant's shoot:root ratio primarily, it is suggested, through differences in amounts of available nitrogen. There was no evidence of changes in beet anatomy in recently-introduced varieties that would result in root material being removed with the crown when samples of delivered, machine-topped beet are contractually de-crowned to estimate crown tares in the factory tarehouse. Variable amounts of crown are removed by harvesting machines. Experiments showed that a greater proportion of beet were over-topped and more root material was removed with the crown when the biological crown was small and when harvester knives were set low to deliver a minimal crown tare. In these situations, significant amounts of root material, for which growers would be paid if delivered to the factory, were left in the field. Data from differential machine-topping trials on commercial sugar beet crops at four locations in 1996 and 1997 were used to relate yield loss through over-topping to crown tare. A crown tare of at least 8% was needed to ensure that no economic yield was left in the field; below this level the losses in delivered yield and grower's income increased exponentially through over-topping. It was estimated from the factory records of individual contracts that deliveries of beet with crown tares below 8% decreased the national adjusted yield of clean beet by 58 400 t in 1997, equivalent to 0.34 t ha^-1 and 0.56% of the total delivered tonnage.     

Respiration Modelling and Hypothesis Testing with a Dynamic Model of Sugar Beet Growth

Respiration was predicted quantitatively during sugar-beet growthsimulations by assuming an intimate coupling to growth and maintenanceprocesses. Changes in the growth and maintenance respiratorycoefficients for successive simulations expressed alternativehypotheses regarding the nature of that coupling. Large differencesin yield, partitioning patterns, and the relative importanceof the growth and maintenance components were predicted in responseto changes in respiratory coefficients within the range consideredphysiologically realistic. Beta vulgaris L, sugar beet, respiration, growth yield, mathematical modelling     

Influence of phloem transport, N-fertilization and ion accumulation on sucrose storage in the taproots of fodder beet and sugar beet

To investigate the factors governing the accumulation of sucroseand amino acids in the taproots of sugar beet, their contentswere measured in the leaves, phloem sap and the taproots ofsugar beet, fodder beet and a hybrid between both, grown oneither 3.0 or 0.5 mM nitrate. In the taproots the contents ofmalate, citrate and inorganic ions were also determined. Forthe high sucrose accumulation in sugar beet as compared to theother varieties three factors were found. (a) In sugar beet,less amino acids and more sucrose are taken up into the phloemthan in fodder beet. (b) In sugar beet, the sucrose and aminoacid syntheses are less sensitive to the nitrate concentrationsthat are required for optimal plant growth than in other varieties.In fodder beet, upon raising the nitrate concentration from0.5 mM to 3 mM, the synthesis and storage of sucrose is decreasedand that of amino acids increased. The corresponding valuesin sugar beet (0.5 mM) are similar to those in fodder beet andare not much affected by an increase of nitrate. (c) The sucroseaccumulation is limited by the accumulation of inorganic ionsin the taproots. The sucrose content in the taproots is negativelycorrelated to the total ion content. Whereas sucrose representstwo-third of all solutes in the taproots of sugar beet, it amountsto only one-third of the solutes in fodder beet taproots. Key words: Amino acids, Beta vulgans L, phloem sap, potassium, sucrose storage, sugar beet, taproots, transport     

Salinity and salt composition effects on seed germination and root length of four sugar beet cultivars

Salinization is one of the most important factors affecting agricultural land in the world. Salinization occurs naturally in arid and semiarid regions where evaporation is higher than rainfall. Sugar beet yield declines with an increase in salinity, but the sensitivity to salts varies with salt composition in water and sugar beet growth stage. The aim of this study was to determine the effect of water salinity levels and salt composition on germination and seedling root length of four sugar beet cultivars (PP22, IC2, PP36, and 7233). The experiments were undertaken with irrigation water with two salt compositions (NaCl alone and mixture of MgSO₄ + NaCl + Na₂SO₄ + CaCl₂) in three replicates. Thirteen salinity levels with electrical conductivity (EC) of the irrigation water ranging from 0 to 30 dS/m were applied to each cultivar in both experiments. Seed germination percentage and seedling root length growth were determined in 13 days. Statistical analysis revealed that germination and root length were significantly affected by salt composition, cultivars and salinity levels. Regardless of salt composition, seed germination and seedling root length were significantly affected by the irrigation water with EC up to 8 dS/m and 4 dS/m, respectively. Except for cultivar PP22, the adverse effect of salinity of the irrigation water on seed germination and seedling root length was higher for NaCl alone than for the salt mixture, which refers to lower salt stress in field conditions with natural salt composition. Presented at the International Conference on Bioclimatology and Natural Hazards, Poľana nad Detvou, Slovakia, 17–20 September 2007.     

Gehalt an Beet Necrotic Yellow Vein Virus (BNYVV) in der Hauptwurzel von Zuckerrübenpflanzen verschiedener Sorten und deren Leistung unter Rizomaniabefall im Feld

BNYVV concentration in the tap roots of sugar beet varieties grown in rhizomania-infested fields During plant development, the BNYVV concentration in several commercially available rhizomania-tolerant sugar beet varieties and one susceptible variety was examined as an index of the intensity of infection. The root weight, sugar content and sugar yield of the same varieties in fields naturally infested with rhizomania were also measured. Significant negative correlations were found between the average virus concentration in the tap root and yield parameters in infested fields. These were largely independent of the growth stage of beet plants used for virological investigations. However, the negative correlations between virus concentration and yield were not significant if rhizomania-tolerant varieties only were compared. The possibility that virus concentration might be used as a criterion for selection in addition to yield performance is discussed. This may lead to selection that is targeted more directly at rhizomania resistance and thereby accelerate breeding work.     

水稻花药水分胁迫培养反应与植株水平抗旱性间的关系

以4个抗旱性不同的水稻品种为材料,研究水分胁迫对花药培养愈伤组织诱导、苗期生长量、成熟期单株产量,以及苗期生理生化指标的影响。结果表明,水分胁迫下,‘沪旱2B’和‘沪旱3号’的花药愈伤组织诱导率、苗期生长量和单株籽粒产量的受抑程度低于‘日本晴’和‘大华香粳’;苗期叶中的脯氨酸（Pro）含量以及过氧化物酶（POD）和超氧化物歧化酶（SOD）活性的受抑程度也是‘沪旱2B’和‘沪旱3号’低于‘日本晴’和‘大华香粳’。表明供试材料离体花药对水分胁迫的培养反应与植株水平的抗旱性存在相关性。     

Growth Habits of Water-stressed Wheat Seedlings as Selection Criteria for Drought Resistance

A technique is described to induce slowly increasing water deficitsin wheat (Triticum aestivum L.) seedlings by rooting them indamp vermiculite and growing them in a humid atmosphere. Aftereight weeks, drought-resistant genotypes can be identified eitherby drought avoidance or by drought tolerance responses. Genotypeswith lesser drought resistance become dormant or produce sterilespikes. The test roughly predicts the relative yield performanceof cultivars in dry field conditions. Triticum aestivum, wheat, matric water deficits, drought resistance, yield selection     

The control of Alternaria species on leaves of sugar beet infected with yellowing viruses

Leaves of virus-free sugar-beet plants rarely became infected with Alternaria spp. in two field experiments at Cambridge in 1965. Infection with beet yellows virus (BYV) increased susceptibility of plants to Alternaria only slightly but infection with beet mild yellowing virus (BMYV) increased it greatly. There was a close association between the severity of Alternaria symptoms, shown by different breeding lines and varieties of sugar beet, and the losses of sugar yield which they sustained after infection with BYV and BMYV. Many lines and varieties were resistant to Alternaria even when infected with BMYV and their resistance seemed to be inherited as a dominant character. Individual plants of any one line or variety differed greatly in resistance to Alternaria, suggesting that selection should improve the present level of resistance. Spraying the foliage of Alternaria-susceptible varieties with fungicides had little effect on the severity of Alternaria symptoms or on sugar yield. This was probably because the wet summer of 1965 was ideal for the spread of Alternaria and because rain washed the fungicide deposits from the sprayed leaves.     

Proteome analysis of sugar beet leaves under drought stress

Drought is one of the major factors limiting the yield of sugar beet (Beta vulgaris L.). The identification of candidate genes for marker-assisted selection (MAS) could greatly improve the efficiency of breeding for increased drought tolerance. Drought-induced changes in the proteome could highlight important genes. Two genotypes of sugar beet (7112 and 7219-P.69) differing in genetic background were cultivated in the field. A line-source sprinkler irrigation system was used to apply irrigated and water deficit treatments beginning at the four-leaf stage. At 157 days after sowing, leaf samples were collected from well-watered and drought-stressed plants for protein extraction and to measure shoot biomass and leaf relative water content. Changes induced in leaf proteins were studied by two-dimensional gel electrophoresis and quantitatively analyzed using image analysis software. Out of more than 500 protein spots reproducibly detected and analyzed, 79 spots showed significant changes under drought. Some proteins showed genotype-specific patterns of up- or downregulation in response to drought. Twenty protein spots were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS), leading to identification of Rubisco and 11 other proteins involved in redox regulation, oxidative stress, signal transduction, and chaperone activities. Some of these proteins could contribute a physiological advantage under drought, making them potential targets for MAS.     

Response of chlorophyll fluorescence parameters to drought stress in sugar beet seedlings

We compared the parameters of chlorophyll fluorescence between two sugar beet (Beta vulgaris L.) species differing in drought tolerance. Our results indicated that there were different responses to the drought stress of these sugar beet species. In drought-tolerant sugar beet, the F ₀ increased slightly, while qN increased substantially, indicating that these plants can protect PSII reaction centers from the damage. F _v/F _m and qP decreased slightly during the initial period of drought stress; this suggests that there is a slight impact of drought stress on the openness of PSII reaction centers, and thus the plants did not suffer seriously. This was further shown by the decreased Yield and electron transfer rate. The parameters of chlorophyll fluorescence were stable and can be used as an important indicator for sugar beet seedlings in the early drought tolerance.     

水分胁迫下内生真菌球毛壳ND35对冬小麦苗期生长和抗旱性的影响

为明确不同水分条件下内生真菌对冬小麦苗期生长和抗旱性的影响,以抗旱型小麦品种山农16和水分敏感型小麦品种山农22为材料,利用荧光定量PCR技术检测小麦干旱诱导基因脱水素wzy2的表达量来了解冬小麦在干旱胁迫下相关基因的表达差异,通过测定相关生理指标与酶活性来判断小麦发育及其在干旱胁迫下的生理响应状况。结果表明,与正常水分ND35组相比,接种球毛壳菌(Chaetomium globosum)ND35的干旱处理组小麦的根冠比、总蛋白含量、脯氨酸含量及丙二醛含量等指标显著提高,小麦叶片含水量和可溶性糖含量有所降低。在干旱处理组中,球毛壳菌ND35可以显著提高小麦山农16的根长和山农22的株高,接种球毛壳ND35的山农16脯氨酸含量、可溶性糖含量、过氧化氢酶活性比对照组均显著提高,丙二醛含量比对照组降低9.0%,但差异不显著;山农22脯氨酸含量和过氧化氢酶活性比对照组显著提高,丙二醛含量和可溶性糖含量比对照组有所降低,但可溶性糖含量差异不显著;相对定量检测数据显示,接种球毛壳ND35后,两种小麦脱水素wzy2基因的表达量较对照组均能够显著提高。综合分析说明内生真菌球毛壳ND35可以促进冬小麦苗期根系和植株发育,小麦提前进入三叶期,增强小麦避旱性,同时提高小麦根系活力,增强小麦耐旱性;提高个体细胞内水分、糖分、脯氨酸含量,降低丙二醛的氧化性损伤,增强过氧化氢酶活性,从而提高两种冬小麦对干旱胁迫的耐受能力;球毛壳ND35促进小麦干旱诱导相关基因wzy2的表达量,进而提高抗旱相关蛋白的表达,从而提高两种冬小麦耐脱水性和对干旱胁迫的适应性。     

Some enzyme changes in chicory (Cichorium intybus) during forcing

Differences in beet weight and sugar concentration of four commercial varieties grown on two types of soil and at different planting density were related to changes in the numbers, sizes and sugar storage capacities of the storage root cells. Much of the variation in beet weight between varieties and soil type was attributable to differences in cell size, less to differences in their number. Differences in weight of beet grown at different densities were caused equally by changes in number of cells and their size. Variation in sugar concentration of the beet was, in all cases, determined more by differences in cell size than in their capacity tostore sugar, but the two factors were not wholly independent of each other.     

The relations between drought susceptibility index based on grain yield (DSIGY) and key physiological seedling traits in maize and triticale genotypes

The physiological reasons for the differences in sensitivity of C₃ and C₄ plant species to environmental stresses have not been thoroughly explained. In this study the effects of drought stress on the growth and selected physiological traits were examined in the seedlings of 13 single cross maize (C₄ plant) hybrids and 11 spring triticale (C₃ plant) breeding lines and varieties differing in drought sensitivity. For plants in the seedling stage the results demonstrated a genetic variation in dry matter accumulation of shoots and roots (DW_S, DW_R), number (N) and length (L) of particular components (seminal, seminal adventitious, nodal) of the root system, membrane injury by soil drought (LI_D), osmotic and high temperature stress (LI_OS, LI_HT), water potential (ψ), water loss (WL), grain germination in osmotic stress (FG, PI), and seedling survival (SS). Seedlings grown under moderate soil drought showed a decrease in dry matter of the top parts and roots and a decrease in the length of seminal, seminal adventitious and nodal roots in comparison to seedlings grown in control conditions. The observed harmful effects of drought stress were more distinct in drought sensitive genotypes. Used in this paper drought susceptibility indexes (DSI_GY) were calculated in other experiment by determining the changes in grain yield (GY) under two soil moisture levels (irrigated and drought). The variation of DSI_GY for maize ranges from 0.381 to 0.650 and for triticale from 0.354 to 0.578. The correlations between DSI_GY and laboratory tests (LI, FG, SS) confirmed that they are good indicators of drought tolerance in plants. The highest values of genetic variation were observed in LI, DW_S, SS and WL and the lowest in the measurements of ψ FG, PI, L_S, L_SA and L_N. The correlation coefficients between LI_OS and LI_HT tests were, in most of the considered cases, statistically significant, which indicates that in maize and triticale the mechanisms of membrane injury caused by simulated drought or high temperature are physiologically similar. It can be concluded that an approach to the breeding of maize and triticale for drought tolerance using these tests can be implemented on the basis of separate selection for each trait or for all of them simultaneously. In that case, it would be necessary to determine the importance of the trait in relation to growth phase, drought timing and level, as well as its associations with morphological traits contributing to drought tolerance. The obtained values of the correlation coefficient between laboratory tests suggest that the same physiological traits may be applied as selection criteria in drought tolerance of maize and triticale genotypes.     

Osmotic adjustment in chickpea (Cicer arietinum L.) results in no yield benefit under terminal drought

Variation in osmotic adjustment (OA) among chickpea (Cicer arietinumL.) cultivars has been observed when exposed to terminal drought,but some studies suggest that this benefits yield while otherssuggest it does not benefit yield in water-limited environments.In the present study, parents differing in OA were crossed anda set of advanced breeding lines (ABLs) developed for yieldtesting. The variation in OA during podding was measured underterminal drought in the F₂, F₃, F₇, and F₈ progeny and in theparents by either rehydrating the leaves before sampling forosmotic potential (OP) or by measuring the relative water content(RWC) and OP on adjacent leaves for the calculation of the OPat full turgor. Yields were measured in the F₈ progeny underterminal drought in Australia and India. While differences inOA were measured in the chickpea lines and parents, OA variedfrom year to year and did not consistently benefit yield whenmeasured in the field under terminal drought. In Australia,differences in OA were not associated with any yield benefitin any year, while in India early flowering resulted in higheryields at three of the four sites, and OA had an inconsistenteffect on seed yields. A comparison of OP at full turgor measuredafter rehydration and from measurements of RWC and OP showedthat the rehydration technique underestimated OA. The lack ofcontribution of OA to yield of chickpea is discussed. Key words: Advanced breeding lines, early flowering, phenology, terminal drought, yield components