Influence of Soil Water Regimes on VA Mycorrhiza IV. Effect on Root Growth and Water Relations of Sorghum bicolor

In a greenhouse trial, non-mycorrhizal and mycorrhizal plants of Sorghum bicolor were grown at three water regimes. The root length and root morphology of Sorghum bicolor was monitored in two soils during 34 days. From 29 days on, total root length of mycorrhizal sorghum was greater than of non-mycorrhizal sorghum in moderate and high water stress conditions. In soil A, at all water regimes a lower percentage of coarse roots and smaller root length per leaf area were found with mycorrhizal plants; in soil B, this was only the case in well watered conditions. In general, all root and water relation parameters were less affected by water stress when plants were mycorrhizal; this less sensitivity of mycorrhizal sorghum may increase the tolerance of the plant to drought. However, water relations of plants were indirectly enhanced by mycorrhiza via increased P uptake.     

Hybrid performance of sorghum and its relationship to morphological and physiological traits under variable drought stress in Kenya

Sorghum, Sorghum bicolor L. Moench, is grown mostly in semi-arid climates where unpredictable drought stress constitutes a major production constraint. To investigate hybrid performance at different levels of drought stress, 12 single-cross hybrids of grain sorghum and their 24 parent lines were grown in eight site-season combinations in a semi-arid area of Kenya. In addition, a subset of 20 genotypes was evaluated at the seedling stage under polyethylene glycol (PEG)-induced drought stress. Environmental means for grain yield ranged from 47 to 584 g/m²reflecting the following situations: two non-stress, one moderate pre-flowering, four moderate terminal and one extreme drought stress. Mean hybrid superiority over mid-parent values was 54% for grain yield and 35% for above-ground biomass. Across environments, hybrids out-yielded two local varieties by 12%. Differences in yield potential contributed to grain yield differences in all stress environments. Early anthesis was most important for specific adaptation to extreme drought. Field performance was not related to growth reduction and osmotic adjustment under PEG-induced drought stress. In conclusion, exploitation of hybrid vigour could improve the productivity of sorghum in semi-arid areas.     

Effect of Drought Stress on Yield and Quality of Maize/Sunflower and Maize/Sorghum Intercrops for Biogas Production

Intercropping represents an alternative to maize (Zea mays L.) monoculture to provide substrate for agricultural biogas production. Maize was intercropped with either sunflower (Helianthus annuus L.) or forage sorghum [Sorghum bicolor (L.) Moench] to determine the effect of seasonal water supply on yield and quality of the above‐ground biomass as a fermentation substrate. The two intercrop partners were grown in alternating double rows at plant available soil water levels of 60–80 %, 40–50 % and 15–30 % under a foil tunnel during the years 2006 and 2007 at Braunschweig, Germany. Although the intercrop dry matter yields in each year increased with increasing soil moisture, the partner crops responded quite differently. While maize produced significantly greater biomass under high rather than low water supply in each year, forage sorghum exhibited a significant yield response only in 2006, and sunflower in none of the 2 years. Despite greatly different soil moisture contents, the contribution of sorghum to the intercrop dry matter yield was similar, averaging 43 % in 2006 and 40 % in 2007. Under conditions of moderate and no drought stress, sunflower had a dry matter yield proportion of roughly one‐third in both years. In the severe drought treatment, however, sunflower contributed 37 % in 2006 and 54 % in 2007 to the total intercrop dry matter yield. The comparatively good performance of sunflower under conditions of low water supply is attributable to a fast early growth, which allows this crop to exploit the residual winter soil moisture. While the calculated methane‐producing potential of the maize/sorghum intercrop was not affected by the level of water supply, the maize/sunflower intercrop in 2006 had a higher theoretically attainable specific methane yield under low and medium than under high water supply. Nevertheless, the effect of water regime on substrate composition within the intercrops was small in comparison with the large differences between the intercrops.     

Fluorimetric Determination of the Genetic Variability Existing for Chilling Tolerance in Sweet Sorghum and Sudan Grass

Chilling temperatures drastically inhibited the photochemical quenching of chlorophyll fluorescence (q_Q) measured in intact leaves photosynthesizing under steady-state conditions. This effect appeared, however, to be characteristic of chilling-susceptible plant species and was not observed in plants which are known to be chilling-tolerant, indicating that the measurement of q_Q can serve in practice to estimate rapidly the relative chilling tolerance of crop plants. A large number (28) of sweet sorghum (Sorghum bicolor) and Sudan grass (Sorghum sudanense) genotypes were screened for chilling tolerance using this rapid q_Q method. Although sweet sorghum and sudan grass obviously behaved as chilling-sensitive plants, a considerable variation for chilling susceptibility was observed among the different genotypes tested. Some sweet sorghum varieties, such as ‘Dale’ and ‘Keller’, and most of the sudan grass varieties appeared to possess a certain degree of resistance towards low temperature stress, indicating the existence of useful germplasms in Sorghum for improving stress tolerance.     

Towards Enhancement of Early‐Stage Chilling Tolerance and Root Development in Sorghum F1 Hybrids

Sorghum (Sorghum bicolor L. Moench) is regarded a drought‐tolerant alternative to maize as a bioenergy and fodder crop, but its early‐stage chilling sensitivity is obstructing a successful implementation in temperate areas. While several studies have identified quantitative trait loci (QTL) underlying chilling tolerance‐related traits in sorghum lines, little is known about the inheritance of these traits in F₁ hybrids. We have conducted a comprehensive approach to analyse heterosis, combining ability and the relation between line per se and hybrid performance for emergence and early shoot and root development comprising both field trials and controlled environment experiments including chilling tests. To our best knowledge, this is the first study analysing heterosis for sorghum root parameters under chilling. Our results show that most traits are heterotic and that the mid‐parent values are rather poor predictors of hybrid performance. Hybrid breeding programmes should focus on efficient GCA tests and the establishment of genetically diverse pools to maximise heterosis rather than on a too strict selection among lines based on their per se performance. The medium‐to‐high heritabilities estimated for seedling emergence and juvenile biomass suggest that a robust breeding progress for these complex traits is feasible.     

Sorghum bicolor prioritizes the recovery of its photosynthetic activity when re-watered after severe drought stress,while manages to preserve it under elevated CO2 and drought

Understanding plant response and resilience to drought under a high CO₂ environment will be crucial to ensure crop production in the future. Sorghum bicolor is a C₄ plant that resists drought better than other crops, which could make it a good alternative to be grown under future climatic conditions. Here, we analyse the physiological response of sorghum under 350 ppm CO₂ (aCO₂) or 700 ppm CO₂ (eCO₂) with drought (D) or without drought (WW) for 9, 13 and 16 days; as well as its resilience under long (R1: 9D + 7R) or short (R2: 13D + 3R) recovery treatments. Sorghum showed elevated rates of gs under aCO₂ and WW, which resulted in a significant decrease in Ψ_w, gs, E, Φ_PSII, F_v’/F_m′ when exposed to drought. Consequently, A was greatly decreased. When re-watered, both re-watering treatments prioritized A recovery by restoring photosynthetic machinery under aCO₂, whereas under eCO₂ plants required little recovery since plant were hardly affected by drought. However, sorghum growth rate for aboveground organs did not reach control values, indicating a slower long-term recovery. Overall, these results provide information about the resilience of sorghum and its utility as a suitable candidate for the drought episodes of the future.     

Comparison of Drought Tolerance of Maize,Sweet Sorghum and Sorghum‐Sudangrass Hybrids

In drought‐prone environments, sweet sorghum and sorghum‐sudangrass hybrids are considered worthy alternatives to maize for biogas production. The biomass productivity of the three crops was compared by growing them side‐by‐side in a rain‐out shelter under different levels of plant available soil water (PASW) during the growing periods of 2008 to 2010 at Braunschweig, Germany. All crops were established under high levels of soil water. Thereafter, the crops either remained at the wet level (60–80 % PASW) or were subjected to moderate (40–50 % PASW) and severe drought stress (15–25 % PASW). While the above‐ground dry weight (ADW) of sweet sorghum and maize was insignificantly different under well‐watered conditions, sweet sorghum under severe drought stress produced 27 % more ADW than maize. The ADW of sorghum‐sudangrass hybrids significantly lagged behind sweet sorghum at all levels of water supply. The three crops differed markedly in their susceptibility to water shortage. Severe drought stress reduced the ADW of maize by 51 %, but only by 37 % for sweet sorghum and 35 % for sorghum‐sudangrass hybrids. The post‐harvest root dry weight (RDW) in the 0–100 cm soil layer for maize, sweet sorghum and sorghum‐sudangrass hybrids averaged 4.4, 6.1 and 2.9 t ha^?1 under wet and 1.9, 5.7 and 2.4 t ha^?1 under severe drought stress. Under these most dry conditions, the sorghum crops had relatively higher RDW and root length density (RLD) in the deeper soil layers than maize. The subsoil RDW proportion (20–100 vs. 0–20 cm) for maize, sweet sorghum and sorghum‐sudangrass hybrids amounted to 6 %, 10 % and 20 %. The higher ADM of sweet sorghum compared with maize under dry conditions is most likely attributable to the deep root penetration and high proportion of roots in the subsoil, which confers the sorghum crop a high water uptake capacity.     

Comparative Effects of Salt and Water Stress on Seed Germination and Early Embryo Growth in Two Cultivars of Sweet Sorghum

In semiarid regions of the Mediterranean basin, water and salinity stresses restrict crop establishment. The effects of salt and water stress on seed germination and early embryo growth (radicle and shoot growth) were investigated in laboratory in two cultivars of sweet sorghum [Sorghum bicolor (L.) Moench] – cv. ‘90‐5‐2′ and cv. ‘Keller’ – to verify how these stresses may limit crop growth during the very early stages of growing season. Six water potentials (ψ) of the imbibition solution (from 0 to ?1.0 MPa) in NaCl or polyethylene glycol (PEG) for salt and water stress tests, respectively, were studied. Daily germination was recorded, and radicle and shoot lengths and dry weights (DWs) were measured 2 days after initial germination. Seed germination was reduced (8–30% lower than control) by water stress at ψ 相似文献   

Independent and Combined Effects of High Temperature and Drought Stress During Grain Filling on Plant Yield and Chloroplast EF‐Tu Expression in Spring Wheat

High temperature and drought stress are among the two most important environmental factors influencing crop growth, development and yield processes. These two stresses commonly occur in combination. Objectives of this research were to investigate the independent and combined effects of high temperature and drought stress during grain filling on physiological, vegetative and yield traits and expression of a chloroplast protein synthesis elongation factor (EF‐Tu) of wheat (Triticum aestivum L.). Two spring wheat cultivars (Pavon‐76 and Seri‐82) were grown at control temperatures (CT; day/night, 24/14 °C; 16/8 h photo/dark period) from sowing to heading. Thereafter, one half of the plants were exposed to high temperature stress (HT; 31/18 °C in Exp. 1 and 34/22 °C in Exp. 2), drought stress (withholding water), or a combination of both HT and drought stress. There were significant influences of HT and/or drought stress on physiological, growth and yield traits. There was no cultivar or cultivar by temperature or cultivar by drought interaction effects on most traits. The decreases in leaf photosynthesis were greater at HT compared with drought alone throughout the stress period, and the combination of HT and drought had the lowest leaf photosynthetic rates. Overall, HT or drought had similar effects (about 48–56 % decrease) on spikelet fertility, grain numbers and grain yield. High temperature decreased grain numbers (by 56 % averaged across both experiments) and individual grain weight (by 25 %), while, respective decreases due to drought were 48 % and 35 %. This suggests that the grain numbers were more sensitive to HT and grain weights to drought for the range of temperatures tested in this research. The interaction between HT and drought stress was significant for total dry weights, harvest index and spikelet fertility, particularly when HT stress was severe (34/22 °C). The combined effects of HT and drought were greater than additive effects of HT or drought alone for leaf chlorophyll content, grain numbers and harvest index. High temperature stress and the combination of HT and drought stress but not drought stress alone resulted in the overexpression of EF‐Tu in both spring wheat cultivars.     

植物非生物胁迫中蛋白质磷酸化的研究进展

作为固着生物,外界生物胁迫和非生物胁迫极大地影响植物的正常生长发育。可逆的蛋白磷酸化作为真核生物体内最普遍的翻译后修饰之一,在植物抵御外界胁迫过程中起着最主要的作用。本综述重点总结了近年来植物在低温、盐渍和干旱等胁迫响应中的蛋白磷酸化研究进展,分析与讨论了其中重要的激酶和磷酸酶的作用,并对此方面的研究热点做了展望。深入了解蛋白磷酸化修饰在植物应对非生物胁迫信号通路中的重要作用及意义,有助于耐胁迫作物的选育。     

Stay green trait in grain sorghum: relationship between visual rating and leaf chlorophyll concentration

Post‐flowering drought tolerance is referred to as the stay green trait in sorghum. Plants with stay green resist drought‐induced premature plant senescence. In breeding programmes, stay green is evaluated under limited irrigation, post‐flowering moisture‐stress field conditions and visually scored at or soon after physiological grain maturity. The objective of this study was to investigate the relationship between the stay green rating and total leaf chlorophyll content. The parents B35 and Tx7000, and their 98 F, recombinant inbred lines were evaluated in replicated field trials under limited (post‐flowering stress) and full‐irrigation (non‐stress) conditions. After scoring the stay green trait of stressed plants, total leaf chlorophyll contents were measured with a chlorophyll meter (SPAD values) and a spectrophotometer method. The SPAD value had a significant linear relationship with total leaf chlorophyll (R²= 0.91) and with visual stay green rating (with R²= 0.82). Relative water content in top leaves of the stay green lines was about 81%, much higher than non‐stay green lines (38%), indicating that the stay green lines kept the stalk transporting system functioning under severe drought conditions, The results indicate that visual stay green ratings were a reliable indicator of leaf senescence an should be useful to sorghum breeders in evaluating progeny when breeding for drought tolerance.     

Respiration and Growth of Sorghum and Sunflower under Predicted Increased Night Temperatures1

Little information exists concerning how crops will respond to the predicted increased night temperatures. The objective of this work was to determine if respiration and growth of sorghum [Sorghum bicolor (L.) Moench], a C, plant, and sunflower (Helianthus annuus L.), a C₃ plant, are affected when the night temperature is increased by 5°C compared to the long-term (19 year) average night temperature in June in Kansas. Sorghum and sunflower were grown in two walk-in growth chambers with either the ambient night temperature (21C) or a high night temperature (26C). Day temperature was the same for all plants (27C). Both sunflower and sorghum had higher respiration rates under the elevated night temperature than under the ambient temperature. The average respiration rate of sunflower grown under elevated night temperature increased by 19% (0.89 vs. 0.75 μmol m^?2 s^?1) and that of sorghum by 44 % (0.52 vs. 0.36μmol m^?2s^?1). After 74 days, sunflower plants grown under the ambient night temperature were 30.2 cm taller than sunflower plants grown under the elevated night temperature; sorghum plants under the ambient temperature were 24.8 cm taller. Sunflower plants grown under the elevated night temperature formed flowers one week earlier than those grown under the ambient temperature. Sorghum formed no flowers by 74 days. Results suggest that, if climate change does increase night temperature, respiration will be increased more in C₄, than C₃ plants.     

Salicylic Acid and Abiotic Stress Responses in Rice

Among plant species rice (Oryza sativa L.) leaves can be characterised with a very high level of salicylic acid content; however, its exact role is still poorly understood. In the present work, rice genotypes with different levels of drought tolerance have been subjected to PEG‐induced drought or cold stress at 10 °C in order to find relationship between the salicylic acid metabolism and the level of stress tolerance; and between the salicylic acid level and other protective mechanisms. Although the drought‐sensitive genotypes usually contained slightly higher amount of salicylic acid than the tolerant ones, there was no strong correlation between the salicylic acid contents and the degree of drought tolerance. Because the expression pattern of the chorismate synthase and isochorismate synthase genes did not correlate with the level of salicylic acid, but there was a correlation between the levels of salicylic acid and ortho‐hydroxy‐cinnamic, it is assumed that the salicylic acid synthesis via ortho‐hydroxy‐cinnamic acid may play a more decisive role than the chorismate–isochorismate–salicylic acid pathway in rice. While the activity of the glutathione reductase enzyme did not show correlation with drought tolerance, the glutathione S‐transferase activities were usually higher in the leaves of the drought‐tolerant varieties than in the sensitive ones. The salicylic acid contents in the leaves were not substantially affected by the applied stress conditions; however, other stress‐related compounds polyamines showed marked, stress‐specific responses. Correlation data suggest that there is no direct link between the abiotic stress‐induced polyamine changes and the salicylic acid metabolism in rice.     

Yield enhancement by short‐term imposition of severe water deficit in the vegetative growth stage of grain sorghum

Water deficit is generally thought to negatively impact crop yields, including grain sorghum (Sorghum bicolor L.), but a small body of literature reports changes in crop physiology and growth in plants with short‐term imposition of water deficit during vegetative development that could lead to increased yield. In a replicated and repeated pot experiment in which water deficit was imposed for 10‐day periods in grain sorghum plants that were otherwise well‐watered, we tested the hypothesis that relatively severe, short‐term water deficit imposed during early vegetative development could enhance grain sorghum yield. The results showed that severe water deficit (~30% of control ET) imposed during two vegetative periods enhanced grain yield compared to continuously well‐watered plants by 21% (p = .0356). Grain yield was correlated with average grain weight, grain number per head and shoot‐to‐root ratio. Yield enhancement was associated with a substantial shift in resource partitioning, as water deficit reduced root mass (p = .0032), stem/leaf mass (p < .0001) and total biomass (p = .0005), resulting in a 60% increase in harvest index. Imposition of water stress during vegetative growth in sorghum can increase grain yield.     

野生大豆S-腺苷甲硫氨酸合成酶基因的克隆及功能分析

干旱、盐碱和低温等非生物逆境是危害作物诸多因素中最为严重的自然灾害, 它可以使作物减产, 甚至死亡。目前通过生物技术手段获得可利用的抗性基因是提高植物抗性的重要途径。东北野生大豆具有丰富的基因资源, 是基因克隆的理想材料。从低温(4℃)、干旱(30%PEG)及盐胁迫(200 mmol L^-1NaCl)处理的东北野生大豆幼苗叶片中提取总RNA, 经反转录合成cDNA第一链, 并以此链为模板, 从已构建的盐胁迫全长cDNA文库和东北野生大豆盐胁迫EST数据库中筛选出与渗透胁迫直接相关的EST序列, 根据该序列设计一对PCR引物扩增S-腺苷甲硫氨酸(SAM)合成酶基因的全长序列, 经Blast比较分析, 确定所获得的SAMS基因全长序列。构建以pBI121为基础的CaMV35S启动子调控的植物表达载体; 利用农杆菌介导法将其导入烟草, 获得了180株转基因烟草, 并进行了低温、干旱和盐胁迫处理, 通过测定在不同胁迫处理下的生理指标, 分析了基因的功能。野生大豆的SAMS基因在烟草中的超量表达提高了转基因烟草的抗低温、干旱和耐盐能力。     

Effects of free‐air CO2 enrichment and drought on root growth of field grown maize and sorghum

Increasing CO₂ concentration ([CO₂]) is thought to induce climate change and thereby increase air temperatures and the risk of drought stress, the latter impairing crop growth. The objective of this study was to investigate the effects of elevated [CO₂] and drought stress on root growth of one maize genotype (Zea mays cv. Simao) and two sorghum genotypes (Sorghum bicolor cv. Bulldozer and Sorghum bicolor × Sorghum sudanense cv. Inka) under the cool moderate climate of Central Europe. It was hypothesized that root growth stimulation due to elevated [CO₂] compensates for a reduced root growth under drought stress. Therefore, we established an experiment within a f ree‐a ir c arbon dioxide e nrichment system (FACE) in 2010 and 2011. Sorghum and maize genotypes were grown under ambient [CO₂] (385 ppm CO₂) and elevated [CO₂] (600 ppm CO₂) and in combination with restricted and sufficient water supply. Elevated [CO₂] decreased root length density (RLD) in the upper soil layers for all genotypes, but increased it in deeper layers. Higher [CO₂] enhanced specific root length (SRL) of “Simao” and “Bulldozer,” however, did not affect that of “Inka.” “Simao” achieved a higher SRL than the sorghum genotypes, indicating an efficient investment in root dry matter. Although elevated [CO₂] affected the root growth, no interaction with the water treatment and, consequently, no compensatory effect of elevated [CO₂] could be identified.     

含ACC脱氨酶的PGPR在植物抗非生物胁迫中的作用研究进展

用含ACC脱氨酶的PGPR接种植物,可降低乙烯含量,从而减轻非生物胁迫对植物生长和发育产生的影响。归纳了水、盐碱、温度、污染物胁迫下含ACC脱氨酶的PGPR对植物的接种效应,得出PGPR可提高植物对干旱、水涝、盐碱胁迫及温度的抗性和耐受性,同时还可促进植物修复土壤污染。最后提出了展望。     

Drought Tolerance and Water Use of Cereal Crops: A Focus on Sorghum as a Food Security Crop in Sub‐Saharan Africa

Sub‐Saharan Africa (SSA) faces twin challenges of water stress and food insecurity – challenges that are already pressing and are projected to grow. Sub‐Saharan Africa comprises 43 % arid and semi‐arid area, which is projected to increase due to climate change. Small‐scale, rainfed agriculture is the main livelihood source in arid and semi‐arid areas of SSA. Because rainfed agriculture constitutes more than 95 % of agricultural land use, water scarcity is a major limitation to production. Crop production, specifically staple cereal crop production, will have to adapt to water scarcity and improved water productivity (output per water input) to meet food requirements. We propose inclusion and promotion of drought‐tolerant cereal crops in arid and semi‐arid agro‐ecological zones of SSA where water scarcity is a major limitation to cereal production. Sorghum uniquely fits production in such regions, due to high and stable water‐use efficiency, drought and heat tolerance, high germplasm variability, comparative nutritional value and existing food value chain in SSA. However, sorghum is socio‐economically and geographically underutilized in parts of SSA. Sorghum inclusion and/or promotion in arid and semi‐arid areas of SSA, especially among subsistence farmers, will improve water productivity and food security.     

Breeding Strategies for Adaptation of Pearl Millet and Sorghum to Climate Variability and Change in West Africa

Semi‐arid and subhumid West Africa is characterized by high inter‐annual rainfall variability, with variable onset of the rainy season, somewhat more predictable endings, and drought or excess water occurrence at any time during the growing season. Climate change is predicted to increase this variability. This article summarizes options for plant breeders to enhance the adaptation of pearl millet (Pennisetum glaucum [L.] R. Br.) and sorghum (Sorghum bicolor [L.] Moench) to climate variability in West Africa. Developing variety types with high degrees of heterozygosity and genetic heterogeneity for adaptation traits helps achieving better individual and population buffering capacity. Traits that potentially enhance adaptive phenotypic plasticity or yield stability in variable climates include photoperiod‐sensitive flowering, plastic tillering, flooding tolerance, seedling heat tolerance and phosphorus efficiency. Farmer‐participatory dynamic gene pool management using broad‐based populations and diverse selection environments is useful to develop new diverse germplasm adapted to specific production constraints including climate variability. For sustainable productivity increase, improved cultivars should respond to farmer‐adoptable soil fertility management and water harvesting techniques. Larger‐scale, on‐farm participatory testing will enable assessments of varietal performance under evolving climatic variability, provide perspective on needs and opportunities and enhance adoption. Strengthening seed systems will be required to achieve sustainable impacts.