Genotypic Variation for Tolerance to Transient Drought During the Reproductive Phase of Brassica rapa

Brassica rapa L. is a genetically diverse parent species of the allotetraploid species, oilseed rape (B. napus) and a potential source of drought tolerance for B. napus. We examined the effect of a 13‐day drought stress period during the early reproductive phase, relative to a well‐watered (WW) control, on subsequent growth and development in nine accessions of B. rapa and one accession of Brassica juncea selected for their wide morphological and genetic diversity. We measured leaf water potential, stomatal conductance, water use, and leaf and bud temperatures during the stress period and aboveground dry weight of total biomass at maturity. Dry weight of seeds and reproductive tissue were not useful measures of drought tolerance due to self‐incompatibility in B. rapa. The relative total biomass (used as the measure of drought tolerance in this study) of the 10 accessions exposed to drought stress ranged from 47 % to 117 % of the WW treatment and was negatively correlated with leaf‐to‐air and bud‐to‐air temperature difference when averaged across the 13‐day stress period. Two wild‐type (B. rapa ssp. sylvestris) accessions had higher relative total and non‐reproductive biomass at maturity and cooler leaves and buds than other types. We conclude that considerable genotypic variation for drought tolerance exists in B. rapa and cooler leaves and buds during a transient drought stress in the early reproductive phase may be a useful screening tool for drought tolerance.     

Selection of wheat genotypes for biomass allocation to improve drought tolerance and carbon sequestration into soils

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought‐stressed and non‐stressed conditions. The experiments were set‐up using a 10 × 10 alpha lattice design with two replications under water stress and non‐stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY). There was significant (p < 0.05) variation for grain yield and biomass production because of genotypic variation. The highest grain yield of 247.3 g/m² was recorded in the genotype LM52 and the least was in genotype Sossognon with 30 g/m². Shoot biomass ranged from 830 g/m² (genotype Arenza) to 437 g/m² (LM57), whilst root biomass ranged between 603 g/m² for Triticale and 140 g/m² for LM15 across testing sites and water regimes. Triticale also recorded the highest R:S of 1.2, whilst the least was 0.30 for wheat genotype LM18. Overall, drought stress reduced total biomass production by 35% and R:S by 14%. Genotypic variation existed for all measured traits useful for improving drought tolerance, whilst the calculated R:S values can improve accuracy in estimating C sequestration potential of wheat. Wheat genotypes LM26, LM47, BW140, LM70, LM48, BW152, LM75, BW162, LM71 and BW141 were selected for further development based on their high total biomass production, grain yield potential and genetic diversity under drought stress.     

Root system plasticity to drought influences grain yield in bread wheat

Crop productivity in semiarid regions is mainly limited by water availability. Root characteristics and plasticity to drought may reduce the negative impact of drought on crop yield. A set of near-isogenic wheat-rye translocation lines was used to test the hypothesis that root system plasticity to drought influences grain yield in wheat. Bread wheat Pavon 76 and 1RS translocation lines, namely Pavon 1RS.1AL, Pavon 1RS.1BL, and Pavon 1RS.1DL were evaluated for root allocation and plasticity in sand-tube experiments under well-watered and droughted conditions across 2 years using factorial treatments in a randomized complete block design with four replicates. The 1RS translocation lines had greater root biomass per plant ranging from 7.37 to 8.6 compared to 5.81 g for Pavon 76. Only Pavon 76 showed a positive response to drought by producing more shallow roots (roots developed between 0 and 30 cm) and deep roots (roots developed below 30 cm) in droughted conditions than in well-watered conditions. Thus at drought intensity of 19% (measured as overall reduction in grain yield), grain yield in Pavon 76 was reduced only by 11% compared to the other genotypes with yield reductions ranging from 18 to 24%. However, at drought intensity of 36%, grain yield in Pavon 76 showed maximum reduction indicating that greater root production under drought is advantageous only when plant-available water is enough to support grain production. Grain yield was positively correlated with shallow and deep root weight and root biomass under terminal drought. Correlation coefficients between root system components (shallow and deep root weight and root biomass) and phenological periods were not significant. Our study indicated that genes influencing adaptive phenotypic plasticity of the root system to drought in Pavon 76 are located on chromosome 1BS.     

Carbon isotope discrimination and water use efficiency relationships of alfalfa genotypes under irrigated and rain-fed organic farming

Carbon isotope discrimination (Δ) has been proposed as a method for evaluating water use efficiency (WUE) in C₃ plants and as a precise technique for screening plants with higer tolerance under water deficit conditions. In this research, 18 alfalfa genotypes from different geographical origins were evaluated under irrigated and rain-fed conditions in organically managed fields in Austria. Significant differences were found amongst harvests for Δ-shoot under both conditions while genotype by harvest interaction was only significant under irrigated condition. Drought stress under rain-fed condition reduced the overall mean of water use efficiency and carbon isotope discrimination responses(up to 34%), but the ratios of reduction differed for characters and genotypes. Narrow ranges were found for all traits especially for WUE-TBY (total biomass yield) (0.78 kg m⁻³) and Δ-shoot (0.53‰) based on genotype means over locations and years, although variation and ranges were higher under irrigated condition. Regarding the variable and low correlations, simultaneous assessment of genotypes for Δ-shoot and biomass production can ensure the selection of superior genotypes and minimize potential biomass reductions that may result from using Δ-shoot as the only selection criterion to improve WUE. Sitel was the most water use efficient genotype(2.79 and 4.48 kg m⁻³ based on shoot dry matter and total biomass,respectively) across two condition (widely adapted genotype) followed by Mohajeran, Fix232 and Verko under irrigated condition (as specific adapted genotypes) and Vlasta, Sanditi, Ghara-aghaj under rain-fed condition.     

Growth and nutrition of cowpea (Vigna unguiculata) under water deficit as influenced by microbial inoculation via seed coating

Drought can drastically reduce cowpea [Vigna unguiculata (L.) Walp.] biomass and grain yield. The application of plant growth‐promoting rhizobacteria and arbuscular mycorrhizal fungi can confer resistance to plants and reduce the effects of environmental stresses, including drought. Seed coating is a technique which allows the application of minor amounts of microbial inocula. Main effects of the factors inoculation and water regime showed that: severe or moderate water deficit had a general negative impact on cowpea plants; total biomass production, seed weight and seed yield were enhanced in plants inoculated with P. putida; inoculation of R. irregularis significantly increased nitrogen (N) and phosphorus (P) shoot concentrations; and R. irregularis enhanced both chlorophyll b and carotenoids contents, particularly under severe water deficit. Plants inoculated with P. putida + R. irregularis had an increase in shoot P concentration of 85% and 57%, under moderate and severe water deficit, respectively. Singly inoculated P. putida improved potassium shoot concentration by 25% under moderate water deficit. Overall, in terms of agricultural productivity the inoculation of P. putida under water deficit might be promising. Seed coating has the potential to be used as a large‐scale delivery system of beneficial microbial inoculants.     

绿豆种质资源成株期抗旱性鉴定

作物种质资源抗旱性鉴定是获得抗旱资源和挖掘抗旱基因的前提。本研究以21份绿豆种质资源为材料,采用温室内盆栽控水旱胁迫,考察不同品种单株产量、单株荚重、单株粒数、单株地上部生物量、单株生物量、根冠比等12项指标,计算各指标在旱胁迫与对照条件下的比值,运用相关性分析、隶属函数、抗旱系数和抗旱指数方法,评价绿豆成株期抗旱性,筛选抗旱优异种质。结果表明,抗旱系数与单株地上部生物量、单株总生物量、单株荚重、单株粒数、单株有效荚数在旱胁迫与对照条件下的比值呈极显著正相关,与根冠比呈极显著负相关,从而遴选出这7项指标作为绿豆成株期抗旱性鉴定的评价指标;基于隶属函数、抗旱系数和抗旱指数三者呈极显著正相关,且3种评价抗旱分级结果一致性较高,故认为抗旱指数法适宜于大规模绿豆成株期抗旱性鉴定;筛选获得高抗种质3份、抗旱种质6份、中抗种质4份、敏感种质5份和极敏感种质3份。     

Genetic and environmental influences on chickpea water‐use efficiency

Chickpea is a major crop grown for its nutritional value, and it is used for both food and feed. However, terminal drought greatly reduces grain yield in many chickpea producing areas. The impacts of drought could be mitigated by adapting chickpea genotypes with higher water‐use efficiency (WUE). To assess genetic variation for WUE, contrasting genotypes were sown in two moisture regimes (well‐watered and water‐limited) and two tillage regimes (tillage and no‐tillage) in north‐western NSW across two consecutive seasons. The well‐watered and no till treatments were higher yielding than their respective rainfed and tillage treatments. Genotypes did not differ (p < 0.05) in their water use but differed significantly in their WUE, and a significant genotype‐by‐moisture treatment effect was observed. The heritability of WUE was higher under tillage (71.3% for tillage under rainfed conditions and 73.0% for tillage and irrigated conditions) than no‐till (43.3% for no till under rainfed conditions and 36.4% for no‐till and irrigated conditions), and no significant genotype‐by‐tillage interaction was observed.     

Screening Wheat (Triticum spp.) Genotypes for Root Length under Contrasting Water Regimes: Potential Sources of Variability for Drought Resistance Breeding

Screening for root traits has been one of the most difficult areas to practise over large number of genotypes. Hydroponic systems enable easy access to roots while high‐molecular weight polyethylene glycol (PEG) is used to induce water stress. A total of 838 genotypes were evaluated for root length in a hydroponic trial under PEG‐induced stress and non‐stress growing conditions. Augmented complete block design with seven blocks and six standard control varieties was used. Root length differences were highly significant (P < 0.01) under both stress and non‐stress growing conditions among genotypes. Osmotic stress has caused an average reduction of 54 % in root length. Among the genotypes, root length ranged from 1.4 to 13.3 cm under stress, and 4.4 to 23.3 cm under non‐stress conditions, respectively. The best control variety for drought resistance was significantly (P < 0.05) outperformed by four new entries namely Colotana 296‐52, Compare, Santa Elena and Tammarin Rock, while the shortest roots were measured on genotypes Aus 16356, Elia, Camm, Portugal 3, and Sentinel. Differences among ploidy levels, domesticated and wild forms were also significant (P < 0.05). Hexaploid wheat showed significantly longer roots in both growing conditions while wild tetraploids showed the shortest roots under stress. There was a change in the ranking of genotypes under the two water regimes, which indicates the difficulty of selecting drought resistant varieties under optimum environments.     

Relationship between Biomass Production and Nitrogen Fixation under Drought-Stress Conditions in Peanut Genotypes with Different Levels of Drought Resistance

The relationship between biomass production and N₂ fixation under drought‐stress conditions in peanut genotypes with different levels of drought resistance is not well understood. The objective of this study was to determine the effect of drought on biomass production and N₂ fixation by evaluating the relative values of these two traits under well watered and water‐stress conditions. Twelve peanut genotypes were tested under field conditions in the dry seasons of 2003/2004 and 2004/2005 in north‐east Thailand. A split‐plot design with four replications was used. Main‐plot treatments were three water regimes [field capacity (FC), 2/3 available soil water (AW) and 1/3 AW], and sub‐plot treatments were 12 peanut lines. Data were recorded on biomass production and N₂ fixation under well watered and water‐stress conditions. Genotypic variations in biomass production and N₂ fixation were found at all water regimes. Biomass production and N₂ fixation decreased with increasing levels of drought stress. Genotypes did not significantly differ in reductions for biomass production, but did differ for reductions in N₂ fixation. High biomass production under both mild and severe drought‐stress conditions was due largely to high potential biomass production under well‐watered conditions and, to a lesser extent, the ability to maintain high biomass production under drought‐stress conditions. High N₂ fixation under drought stress also was due largely to high N₂ fixation under well‐watered conditions with significant but lower contributions from the ability to maintain high nitrogen fixation under drought stress. N₂ fixation at FC was not correlated with the reduction in N₂ fixation at 2/3 AW and 1/3 AW. Positive relationships between N₂ fixed and biomass production of the tested peanut genotypes were found at both levels of drought stress, and the relationship was stronger the more severe the drought stress. These results suggested that the ability to maintain high N₂ fixation under drought stress could aid peanut genotypes in maintaining high yield under water‐limited conditions.     

Characterization of Drought‐Tolerance Traits in Nodulated Soya Beans: The Importance of Maintaining Photosynthesis and Shoot Biomass Under Drought‐Induced Limitations on Nitrogen Metabolism

Drought is the single most important factor limiting soya bean (Glycine max L. Merr.) yields in the field. The following study was therefore undertaken to identify phenotypic markers for enhanced drought tolerance in nodulated soya beans. Leaf and nodule parameters were compared in three genotypes: Prima 2000, glyphosate‐resistant A5409RG and Jackson, which had similar shoot biomass and photosynthesis rates at the third trifoliate leaf stage under water‐replete conditions. When water was withheld at the third trifoliate leaf stage, photosynthesis, nodule numbers, nodule biomass and symbiotic nitrogen fixation (SNF) were greatly decreased. Significant cultivar–drought interactions were observed with respect to photosynthesis, which also showed a strong positive correlation with nodule SNF, particularly under drought conditions. Prima leaves had high water‐use efficiencies, and they also maintained high photosynthetic electron transport efficiencies under long‐term drought. Moreover, Prima had the highest shoot biomass under both water‐replete and drought conditions. A‐5409RG was the most drought‐sensitive genotype showing early closure of stomata and rapid inhibition of photosynthesis in response to drought. In addition to classifying the genotypes in relation to drought tolerance, the results demonstrate that the ability to sustain shoot biomass under nitrogen limitation is an important parameter, which can be easily applied in germplasm screening for drought tolerance in soya bean.     

Spatial difference of drought effect on photosynthesis of leaf subtending to cotton boll and its relationship with boll biomass

The leaf subtending to a cotton boll (LSCB) is vital to boll development and biomass, but few studies have examined the effects of drought on the source capacity of LSCBs on different fruiting branches (FBs). To investigate the response of LSCB photosynthesis on different FBs and the relationship of boll biomass to drought, a drought experiment was performed with three treatments: well‐watered (WW, soil water relative content [SRWC] 75 ± 5%), mild drought (MD, SRWC 60 ± 5%), and severe drought (SD, SRWC 45 ± 5%). Despite photosynthetic active radiation increasing under drought conditions, the pre‐dawn leaf water potential, net photosynthesis rate (Pn), stomatal conductance (Gs), transpiration rate (Tr), and maximum quantum yield in PSII (Fv/Fm) under MD and SD significantly decreased when compared with WW, with a more pronounced decrease observed on upper FBs. Additionally, the maximum sucrose and hexose levels in LSCBs increased under drought conditions, whereas the maximum starch content decreased on FB_10–11, but showed a varied trend on FB_2–3 and FB_6–7. Although carbohydrate levels in the LSCBs increased, biomass per cotton boll decreased. More importantly, the ratio of cotton boll biomass was significantly correlated to the maximum sucrose content ratio on each FB, indicating that sucrose allocation was important to cotton boll biomass. Cotton boll biomass notably decreased on upper FBs, but was maintained on lower FBs, indicating that drought promoted carbon allocation in older bolls. Thus, LSCBs and cotton bolls on upper FBs were more affected under drought conditions due to decreased photosynthesis and carbohydrate allocation.     

Drought resistance of potato cultivars with contrasting canopy architecture

There has been little research in potatoes (Solanum tuberosum L.) to define the ideal canopy structure for obtaining high and stable tuber yields. Two field experiments were conducted on a loamy sand soil (Haplic Luvisol) near Braunschweig in the North German Plain. The eight medium late potato cultivars grown in the year 2000 under non-limiting conditions differed significantly (P < 0.05) for leaf and stem dry weight, leaf/stem mass ratio, leaf number, leaf area, and other canopy structure parameters. Genotypes characterised by a high leaf/stem ratio (leaf-types) produced a lower shoot biomass than those with a low leaf/stem ratio (stem-types). The cultivars Producent and Tomba, representing a leaf- and a stem-type, respectively, were chosen to study the relationship between shoot and tuber yield under rainfed and irrigated conditions during the years 2001–2003. Different seasonal rainfall together with varying levels of extra water from irrigation created a wide range of soil moisture levels. The detrimental effects of drought on light interception were much greater for the leaf-type than for the stem-type. Under rainfed conditions, the relative tuber dry weight of the stem-type as compared with the leaf-type amounted to 99% in the absence of drought (2002), 109% under moderate drought (2001), and 148% under severe drought (2003). Obviously, the ability of stem-types to form a greater aboveground biomass is especially advantageous under soil water deficit conditions. High availability of water under irrigation in the years 2002 and 2003 produced a canopy size in the stem-type in excess of that required for maximum light interception. Consequently, the tuber dry weight of the stem-type displayed an optimum relationship with the shoot dry weight whereas the tuber yield of the leaf-type increased linearly with the shoot yield.     

Forage legumes for future dry climates: Lower relative biomass losses of minor forage legumes compared to Trifolium repens under conditions of periodic drought stress

Dairy livestock production systems rely on high‐quality forage legumes, which are widely present in grassland swards all over Europe. A future climatic scenario with higher average annual temperatures and lower precipitation is expected to affect grassland productivity in general and the productivity of the most important forage legume species Trifolium repens in particular. One way to cope with such constraints is the adoption of currently underutilized minor legume species with a higher tolerance towards drought stress. Therefore, the present study investigated legume species with lower moisture requirements than T. repens, these are Lotus corniculatus, Medicago falcata, Medicago lupulina and Onobrychis viciifolia in comparison with T. repens. Legumes were grown in containers as monocultures in a roofed open‐sided greenhouse under conditions of optimal water supply or periodic drought stress. Generally, drought stress decreased the biomass production, but species differed in their reaction. Particularly, M. lupulina and L. corniculatus had lower relative biomass losses (?26%) compared to T. repens (?43%, as averaged over drought stress periods). However, in overall biomass production T. repens still was at one level with M. lupulina and L. corniculatus under drought stress. This was related to high stomata control as indicated by the intrinsic water‐use efficiency. We conclude that there are promising future options of forage legumes as alternatives to T. repens.     

Photosynthesis and Remobilization of Dry Matter in Wheat as Affected by Progressive Drought Stress at Stem Elongation Stage

With increasingly erratic rainfall patterns particularly in drought‐prone production systems, the capacity of plants to recover productively from drought spells becomes an important feature for yield stability in rainfed agriculture. Consequently, effects of water management at the stem elongation stage on partitioning and remobilization of dry matter, alteration in photosynthesis and water‐use efficiency (WUE), and yield components of wheat plants were studied in a glasshouse pot experiment. The plants were subjected to three soil moisture regimes: well watered during all phenological stages (WW), drought affected during stem elongation and post‐anthesis stages (DD) and drought affected during stem elongation and rewatered at post‐anthesis stage (DW). Total dry weight substantially decreased by both drought treatments. However, DD plants allocated relatively higher assimilates to roots whereas DW plants remobilized them to the grains. Drought applications resulted in a decrease of grain yield and thousand grain weight while reduction was more pronounced in DD treatment. Relative contribution of post‐anthesis photosynthesis to dry matter formation in grain was higher in WW treatment (72.6 %) than DD (68.5 %) and DW (68.2 %) treatments. Photosynthetic rate, gas exchange and transpiration decreased whereas leaf (photosynthetic) and plant level WUE increased with drought applications. However, all these parameters were rapidly and completely reversed by rewatering. Our findings showed that partitioning of dry weight to grain increases with rewatering of wheat plants subjected to drought during stem elongation phase, but the relative contributions of remobilization of stem reserves and post‐anthesis photosynthesis to grain did not change. Moreover, rewatering of plants at booting stage after a drought period lead to full recovery in photosynthesis and WUE, and a significant although partial recovery of yield components, such as grain yield, TGW and harvest index.     

The Response of the Leguminous Fodder Plant Bituminaria bituminosa to Water Stress

Abstract Bituminaria bituminosa (L.) C.H. Stirton (Fabaceae) is a biennial–perennial species, which grows throughout the Mediterranean basin and Macaronesia. It is cultivated to provide livestock fodder and shows promise as a source of furanocoumarins. This is the first report on its physiological and growth responses to water deprivation. We assessed these in a pot assay, in the field and in hydroponic culture, using two populations from southern Spain and two from the Canary Islands. Proline accumulation was much lower in the field than for pot‐grown plants, supporting recent indications that it is phytotoxic under combined drought and heat stress. In hydroponic culture, imposition of water stress by poly(ethylene glycol) increased the root/shoot ratio and decreased the root hydraulic conductivity. Overall, the results show B. bituminosa to be a species with high constitutive resistance to soil water deficit. For example, leaf turgor did not diminish, demonstrating its capacity for osmotic adjustment, and the specific leaf area in field conditions was similar to that of other species adapted to seasonal drought. Notwithstanding, the two Canarian populations (which complete their life cycles under very different conditions) maintained better their relative water content and water potential to avoid internal stress. Famara (Lanzarote, Canary Islands) is the most appropriate as a breeding line, which can maintain its shoot biomass under drought.     

Water Use Efficiency, Carbon Isotope Discrimination and Biomass Production of Two Sugar Beet Varieties Under Well-Watered and Dry Conditions

Two sugar beet (Beta vulgaris sp.) varieties, which were supposed to differ in drought tolerance, were exposed to drought stress in a growth chamber and a container experiment in field. The aim was to test for (i) differences between the varieties in water use efficiency (WUE), biomass production and distribution and (ii) the relationship between WUE and carbon isotope discrimination (Δ), and between biomass production and Δ. Significant differences in WUE were detected between plants of well‐watered and drought treatments in both experiments, but not between the varieties. Production losses due to drought were large for both varieties in both experiments. Losses in the growth chamber were up to 50 % of plant dry weight and the corresponding value in the field was 24 %, when plants were given 60 and 30 %, respectively, of the full‐watered treatments. Significant negative correlations between WUE and Δ were found, but not between biomass production and Δ, when both varieties were included. Negative correlations between WUE and Δ were also found for each variety separately. The results suggest that Δ estimates from leaf tissue of sugar beet may provide a useful tool for genetic selection of drought‐tolerant sugar beet varieties.     

Variance components and heritability of traits related to root: shoot biomass allocation and drought tolerance in wheat

Enhanced root growth in plants is fundamental to improve soil water exploration and drought tolerance. Understanding of the variance components and heritability of root biomass allocation is key to design suitable breeding strategies and to enhance the response to selection. This study aimed to determine variance components and heritability of biomass allocation and related traits in 99 genotypes of wheat (Triticum aestivum L.) and one triticale (X. Triticosecale Wittmack) under drought-stressed and non-stressed conditions in the field and greenhouse using a 10?×?10 alpha lattice design. Days to heading (DTH), days to maturity (DTM), number of tillers (NPT), plant height (PH), spike length (SL), shoot and root biomass (SB, RB), root to shoot ratio (RS), thousand kernel weight (TKW) and yield (GY) were recorded. Analyses of variance, variance components, heritability and genetic correlations were computed. Significant (p?<?0.05) genetic and environmental variation were observed for all the traits except for spike length. Drought stress decreased heritability of RS from 47 to 28% and GY from 55 to 17%. The correlations between RS with PH, NPT, SL, SB and GY were weaker under drought-stress (r?≤???0.50; p?<?0.05) compared to non-stressed conditions, suggesting that lower root biomass allocation under drought stress compromises wheat productivity. The negative association between GY and RS (r?=???0.41 and ??0.33; p?<?0.05), low heritability (<?42%) and high environmental variance (>?70%) for RS observed in this population constitute several bottlenecks for improving yield and root mass simultaneously. However, indirect selection for DTH, PH, RB, and TKW, could help optimize RS and simultaneously improve drought tolerance and yield under drought-stressed conditions.     

Screening Saccharum Barberi and Sinense Accessions for Flood Tolerance and Biomass Production

This study evaluated the biomass production potential of Saccharum barberi (Jeswiet) and Saccharum sinense (Roxb. Amend. Jeswiet) accessions under short‐term flooded conditions. Plots were arranged in a completely randomized design with 20 S. sinense and 29 S. barberi accessions, two flood durations with non‐flooded controls and three replications of each treatment. There were no significant flood effects. However, in two individual accessions, ‘China’ and ‘Lu Cane’, sucrose production increased with additional flooding. The plant cane produced larger plants with a greater percentage of fibre and sucrose. Higher Brix values were obtained with the ratoon crop. Brix and fibre were negatively correlated with stem diameter. Stem length in S. barberi was the only physical characteristic that was correlated with sugar factors Brix and optical rotation. S. barberi accessions had high loadings for variables associated with sugar production and stem length, and fibre had moderate loadings for factor 1. Factor 1 explained 35 % of variance in the data. The second principal factor revealed high loadings for variables associated with plant size. Factor 2 explained 30 % of the proportional and together with Factor 1 explained 65 % of the cumulative variance in the data. Several accessions with low sucrose, high plot weight and low fibre were identified. These accessions make attractive selections in breeding for biomass production.     

Growth and Physiological Responses of Quinoa to Drought and Temperature Stress

Quinoa (Chenopodium quinoa Willd.), traditionally called the mother of grains, has the potential to grow under high temperatures and drought, tolerating levels regarded as stresses in other crop species. A pot experiment was conducted in a climate chamber to investigate the potential of quinoa tolerance to increasing drought and temperature. Quinoa plants were subjected to three irrigation and two temperature regimes. At low temperature, the day/night climate chamber temperature was maintained at 18/8 °C and 25/20 °C for high temperature throughout the treatment period. The irrigation treatments were full irrigation (FI), deficit irrigation (DI) and alternate root‐zone drying (ARD). FI plants were irrigated daily to the level of the pot's water‐holding capacity. In DI and ARD, 70 % water of FI was applied either to the whole pot or to one side of the pot alternating, respectively. The results indicated that plant height and shoot dry weight significantly decreased by ARD and DI compared to FI treatment both at low and at high temperatures. However, plants in ARD treatment showed significantly higher plant height and shoot dry weight compared to DI especially at higher temperature, which is linked to increased xylem ion content. Higher quinoa plant growth in ARD was associated with increase in water‐use efficiency (WUE_i) due to higher abscisic acid concentration and higher nutrient contents compared to DI. From results, it can be concluded that quinoa plant growth is favoured by high temperature (25/20 °C) and ARD is an effective irrigation strategy to increase WUE in drought prone areas.     

水分胁迫下紫花苜蓿根系特征与ABA含量的变化

研究通过温室盆栽试验探讨了干旱胁迫对‘三得利’、‘敖汉’和‘中苜1 号’3 个紫花苜蓿品种根系ABA浓度和根系特征的影响。按照田间持水量的100%（对照）、85%（轻度干旱）、70%（中度干旱）和55%（重度干旱）设置4 个梯度的水分胁迫处理,分别对3 个紫花苜蓿品种进行处理,并对根系ABA含量和根系性状进行测量。结果显示：水分胁迫可以显著影响不同生长时期的紫花苜蓿根系ABA的含量。随着处理时间的延长,不同水分胁迫处理的紫花苜蓿根系ABA含量均呈先升高后下降再升高的趋势。在移栽后的第75 天,根系ABA含量达到首个峰值,然后开始下降,到第105 天的时候将至最低,然后开始回升直至处理结束。移栽105 天以后,4 个水分胁迫处理（W1、W2、W3 和W4）紫花苜蓿根系ABA含量分别为44、56.6、64.6、94.4 ng/g FW。同时,不同紫花苜蓿品种根系ABA含量存在差异。移栽105 天以后,‘敖汉’、‘三得利’和‘中苜1 号’根系ABA含量均达到最低,分别为83.2 ng/g FW、61.7 ng/g.FW 和49.9 ng/g FW;之后,根系ABA含量开始回升。与对照相比,重度水分胁迫使根系长度降低了20.92%,使侧根数降低了20.71%,使根鲜重降低了43.79%,使根干重降低了37.96%。重度水分胁迫下植株根冠比是对照的1.9倍,这说明水分胁迫对地上部茎叶的影响要大于地下部的根系。水分胁迫降低了紫花苜蓿根长、侧根数、根鲜重和根干重,增加了紫花苜蓿根冠比,促使根系ABA含量升高。不同紫花苜蓿品种根系ABA含量存在差异。