Influence of nitrogen deficiency or excess on a root system structure of maize and triticale seedlings grown under low and high soil density

Responses of maize and triticale seedlings, differing in the susceptibility to soil density stress, and grown under low (L_D) or high (H_D) soil density and poor (P_N), high (H_N) or control (C_N) nitrogen content in soil were investigated in relation to changes in physiological parameters—dry matter of shoot (S), root (R), shoot to root ratio (S/R), relative growth ratio of shoot and root (RGR), chlorophyll content (SPAD), total roots number and length (TRN, TRL), root penetration ability (RPA) and ratio of deep rooting (RDR). The seedlings grown under high soil density (H_D) and control N‐soil content (C_N) in comparison with L_D and C_N treatments showed a decrease in all measured parameters. Under poor and high nitrogen content, changes in the traits were higher for triticale than for maize. Higher differences between resistant and sensitive genotypes in TRN, TRL, RPA and RDR were observed particularly in the seedlings grown under H_D treatment. Differences in parameters values between seedlings grown under control and nitrogen‐rich soil may be considered as a positive interaction between stresses. Our results suggest that the type of root structure (scattered, dimorphic) would be helpful in enhancing modelling and agronomic management for improved of plant stress tolerance.     

Effect of soil drought on growth and yield of maize (Zea mays L.) hybrids grown under compacted soil

In this study, we examined responses of maize hybrids differing in susceptibility to soil compaction and drought in the case of their separate or combined action. We ran field and greenhouse experiments and determined effects on grain yield, biomass, weight of 1000 grains, shoot and roots dry matter (DM), shoot-to-roots ratio, harvest index, plant height, emergence index, leaf area and greening and root number and length. Individual and combined effects of both stresses were observed in the field and greenhouse. Compared with plants growing in loose soil and optimal irrigation (LI), the resistant hybrids in treatments HI, LD and HD showed a smaller reduction in GY, BY, S, R, R_N and R_L than the sensitive. In both groups, stress influence on HA, W-1000, LA and SPAD was smaller and the differences were insignificant. Compared with LI treatment, the roots of LD, HI and HD increased their DM, number and length in the upper level of the soil profile and the number of roots developed at 0–30° and 30–60° in relation to the root main axis. Analysis of those traits in the hybrids resistant and sensitive to both stress factors enabled to explain a defence response. Our study demonstrated that soil compaction and soil drought, which usually occurs simultaneously, caused significant changes in components of plant yield and showed plant plasticity in response to environmental factors under natural conditions.     

Drought effects on yield and its components in Indian mustard (Brassica juncea L.)

Effects of drought on yield and yield components were investigated during the spring season 2000–2001 by growing 14 Indian mustard genotypes under irrigated and rain-fed conditions at Bharatpur and Jobner. A disease and pest management schedule was followed when required. The drought susceptibility index (DSI) for seed yield and component characteristics was calculated to characterize the relative tolerance of genotypes. Plant height, primary branches, secondary branches per plant, 1000-seed weight and seed yield were reduced under rain-fed conditions. The top five genotypes at Bharatpur that showed tolerance to moisture stress for seed yield, as indicated by their lowest DSI, were, in descending order PSR-20, PRO-97024, JMMWR-941, IS-1787 and PCR-7, whereas at Jobner these were JMMWR-941, RC-1446, PSR-20, RH-819 and 'Varuna'. Of these, PSR-20 and JMMWR-941 were among the top six at both locations. These genotypes also showed relatively low DSI for one or more characteristics, such as primary branches per plant, secondary branches per plant, harvest index and seed : husk ratio. Genotypes with the lowest DSI, particularly for seed yield at both locations, would serve as useful donors in the breeding programme for improving the drought tolerance of existing Indian mustard cultivars.     

Stress tolerance in hexaploid spring triticale under Mediterranean environment

The development of triticale (X Triticosecale Wittmack) cultivars which are tolerant to drought and heat stress is an objective in many breeding programmes, but so far success has been limited. This study was conducted to determine the susceptibility index (S) of triticale under stress conditions. Twenty genotypes were grown in replicated trials and evaluated for heat and drought tolerance under natural conditions at Adana, Turkey, from 1992 to 1996. Among the advanced lines of triticale, genetic variation for adaptation to heat and drought conditions—typical features of the Mediterranean environment—was determined. The best yielding lines under stress, hence having a low susceptibility index, were Lynx/Yogui and Zebra 31. The implications of these findings for triticale breeding in stress environments are discussed.     

花后干旱和渍水对冬小麦光合特性和物质运转的影响

在温室盆栽条件下，以黑小麦76、皖麦38、扬麦10号、扬麦9号4个蛋白质含量不同的冬小麦(Triticum aestivum L.) 基因型为材料，研究了花后土壤干旱（Soil relative water content, SRWC=45%～50%）、渍水和适宜水分条件（SRWC=75%～80%）下，小麦旗叶净光合速率和叶绿素含量的动态变化，营养器官花前贮藏同化物再运转，花后同     

Chemical priming with urea and KNO<Subscript>3</Subscript> enhances maize hybrids (<Emphasis Type="Italic">Zea mays</Emphasis> L.) seed viability under abiotic stress

Seed priming is a method to improve germination and seedling establishment under stress conditions. The effect of seed priming in chemical solutions such as urea and KNO₃, on protein and proline content, germination, and seedling growth responses of four maize (Zea mays L.) hybrids under drought and salt stress conditions was studied in a controlled environment in 2010. Treatments included stress type and intensity at five levels: moderate drought (MD), severe drought (SD), moderate salt (MS), severe salt (SS), and control (C1, without stress), three seed priming types including water (C2, as control), KNO₃, and urea (as chemical priming), and four maize hybrids including Maxima, SC704, Zola, and 307. The results showed that the highest germination percentage (Ger %), germination rate (GR), seedling length (SL), radical length (RL), and seedling to radical length ratio (S/R) were achieved in no stress treatments and most proline content in SD treatment. Urea priming led to more Ger%, GR, and SL compared to other primers and treatment under KNO₃ priming resulted in higher RL compared to other primers. Chemical priming had no effect on S/R and proline content. Also, in terms of most traits, no difference was found among the four hybrids. Results showed that salt stress could affect GR and RL more than the drought stress. Drought stress affected germination percentage and S/R more than the salt stress. Both stresses decreased all measured parameters, except protein and proline content which were increased remarkably, and more under drought compared to salt stress. Based on proline content, hybrid 304 appeared to be more resistant to stress than other hybrids. Generally, KNO₃ and urea alleviated effects of both stresses and led to increased germination and seedling growth as well as the root length. Therefore, priming could be recommended for enhancing maize growth responses under stressful conditions.     

S3307对始花期和始粒期淹水绿豆光合作用及产量的影响

淹水胁迫是作物生长发育过程中遭受的主要非生物胁迫之一,探究提高绿豆耐淹性的机制对绿豆抗涝栽培具有重要意义。本文在2017—2018年以耐淹性不同的绿豆品种绿丰2号和绿丰5号为试验材料,采用盆栽方式探究了烯效唑(S3307)对淹水胁迫下绿豆叶片生理、光合作用及产量的影响。结果表明,在不同生育时期淹水胁迫下,绿豆叶片的叶绿素含量(SPAD)及光合特性参数均显著下降,丙二醛(MDA)含量显著增加,始花期(R1期)淹水胁迫下绿豆的减产率为24.70%～33.63%,始粒期(R5期)减产率为18.07%～28.87%。2个绿豆品种均表现为R1期受淹水胁迫危害程度大于R5期,绿丰2号耐淹性强于绿丰5号。喷施S3307后显著提高淹水胁迫下绿豆叶片的SPAD、净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs),并显著降低了MDA含量。绿豆在R1期淹水胁迫下的缓解率为28.91%～52.34%,R5期缓解率为13.77%～27.36%。表明叶面喷施S3307可有效提高淹水胁迫下绿豆叶片的生理功能及光合能力,进而降低减产幅度,但不同淹水时期和绿豆品种对S3307的调控响应存在差异。     

花铃期不同钾效率基因型棉花对干旱和低钾胁迫的响应差异

以钾高效和钾低效基因型棉花(HEG和LEG)为试验材料,研究了最优水肥(W1K1),干旱胁迫(W2K1),低钾胁迫(W1K2),干旱、低钾胁迫(W2K2)对其光合作用及水分、钾素利用率的影响。结果表明:干旱显著降低花铃期2种基因型棉花叶片净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr),导致蕾铃脱落,钾素利用率(KUE)降低,造成棉花减产。施钾促进叶片Pn及水分利用率(WUE)的提高,但基因型间存在差异,LEG叶片WUE与施钾量成正比,HEG相反。低钾胁迫下HEG的Pn、Tr下降,但Pn下降幅度小于Tr,WUE增大。较高的WUE有利于提高棉花Pn,降低蕾铃脱落率,促进钾素的高效吸收和运输。     

Response of Sorghum to Abiotic Stresses: A Review

Sorghum [(Sorghum bicolor L.) Moench] is a highly productive crop plant, which can be used for alternative energy resource, human food, livestock feed or industrial purposes. The biomass of sorghum can be utilized as solid fuel via thermochemical routes or as a carbohydrate substrate via fermentation processes. The plant has a great adaptation potential to drought, high salinity and high temperature, which are important characteristics of genotypes growing in extreme environments. However, the climate change in the 21st century may bring about new challenges in the cultivated areas. In this review, we summarize the most recent literature about the responses of sorghum to the most important abiotic stresses: nutrient deficiency, aluminium stress, drought, high salinity, waterlogging or temperature stress the plants have to cope with during cultivation. The advanced molecular and system biological tools provide new opportunities for breeders to select stress‐tolerant and high‐yielding cultivars.     

How does water and salt stress affect the germination and initial growth of Brazilian soya bean cultivars?

The effects of water and salt stress on rate of germination and seedling growth were investigated under laboratory conditions in 46 soya bean genotypes from Central-West region of Brazil to verify how these stresses may limit crop establishment during the initial growth stage and also to identify the most tolerant genotypes to drought and salinity. Mild water and salt stresses were imposed by seed exposure to –0.20 MPa iso-osmotic solutions with polyethylene glycol—PEG 6000 (119.57 g/L) or NaCl (2.357 g/L) for 12 days at 25°C. The germination percentage, seedling length and seedling dry matter were measured, and then, salt or drought tolerance indexes were calculated. The “NS 5909 RG,” “NS 7000 IPRO,” “NS 7338IPRO,” “FPS Solimões RR,” “NS 5151 IPRO,” “SYN 13610 IPRO,” “LG 60177 IPRO,” “NS 6909 IPRO” and “BMX Desafio RR” were identified as the most drought-tolerant genotypes, whereas under salinity conditions, the genotypes “5D 615 RR,” “BMX Desafio RR,” “5D 6215 IPRO” and “BMX Ponta IPRO” were identified as tolerant. The “BMX Desafio RR” is the genotype most adapted to both stress conditions and, therefore, should be used under conditions of water shortage and excess salt in the soil at sowing time.     

Evaluation of Yield Criteria for Drought and Heat Resistance in Chickpea (Cicer arietinum L.)

The chickpea (Cicer arietinum L.) is usually grown under rainfed, rather than irrigated conditions, where drought accompanied by heat stress is a major growth constraint. The aim of this study was to select chickpea genotypes having resistance to drought/heat stress and to identify the most appropriate selection criteria for this. A total of 377 chickpea accessions were sown 2 months later than normal for the Antalya region (Turkey) to increase their exposure to the drought and high‐temperature conditions of a typical summer in this part of the world. Interspersed between every 10 test genotypes as benchmark genotypes, were plants of the two known genotypes ILC 3279 (drought‐susceptible) and ILC 8617 (drought‐susceptible), while ICC 4958 (known drought‐resistant) and ICCV 96029 (known very early, double‐podded) were also sown for confirmation. All plants were subsequently screened for drought and heat stress resistance. Soon after the two known susceptible genotypes had died, evaluations of the entire trial were made visually on a scale from ‘1’ (free from drought/heat damage) to ‘9’ (all plants died from drought/heat). Yield loss in many of the test genotypes and in the two known susceptible genotypes (ILC 3279 and ILC 8617) rose to 100 %. The desi chickpeas (smaller, dark seeds) were generally more drought‐ and heat‐resistant than the kabuli chickpeas (larger, pale seeds). Two desi chickpeas, ACC 316 and ACC 317, were selected for drought and heat (>40 °C) resistance under field conditions. Seed weight was the trait least affected by adverse environmental conditions and having the highest heritability, and it should be used in early breeding selections. When breeding drought‐ and heat‐resistant chickpeas, path and multivariate analyses showed that days to the first flowering and maturity to escape terminal drought and heat stresses should be evaluated ahead of many other phenological traits, and harvest index, biological yield and pods per plant for increased yield should also be considered.     

Screening for Drought Resistance: Evaluation of Drought Susceptibility Index of Legume Plants under Natural Growth Conditions

Eighteen cultivars of legume species (field bean, soybean, field pea, lupine) were screened for drought tolerance in 3 year-long field experiments. The aim of the investigations was to evaluate the generic variation of drought susceptibility of the tested varieties. The experimental plots were equipped with an installation which enabled the limitation of the water content in soil and soil irrigation. The applied drought susceptibility index (DSI) considered the relations between seed yield of plants under drought conditions (Y_D) and that under conditions of good soil watering (Y_IR) as well as their dependence on the drought severity index (D_S). The use of the index divided the cultivars into two groups of different drought tolerances. The group of drought resistant cultivars characterized by mean values of the DSI index < 0.31 comprised field bean cultivars Bourdon, Gobo and Nadwislanski, soybean cultivars Aldana, Polan and Progres, field pea cultivars Miko and Solara and lupine cultivars Popiel and Bac. To the drought sensitive cultivars with DSI > 0.44 belonged Victor and Bronto of field bean species, Bareness and Mige of field pea species and Emir of lupine species. In general, the resistant cultivars when compared with the susceptible ones were characterized by lesser yield of seeds, which, however, was more stable both under conditions of drought and moistured plots. Any dependence of the degree of drought tolerance on the duration of the particular periods of plant growth was not observed in the experiments, however, both in’ drought susceptible and drought resistant cultivars there appeared the tendency to shorten the development phases under drought and to prolong them under artificial irrigation. In general, based on the results obtained, it can be concluded that legume plants belong to the species sensitive to water supply. The observed decrease of plant seed yield under moderate natural soil dryness in the year 1993 differed only a little from that found in experiments in the years 1994 and 1995, when soil dryness was much more severe.     

小麦水分胁迫影响因子的定量研究 Ⅱ.模型的建立与测试

基于冬小麦水分生理生态关系，综合考虑土壤水分有效性、作物不同生育阶段对干旱或渍水胁迫的敏感性、作物主要生理过程（蒸腾、光合作用、干物质分配等）对干旱胁迫的差异性、渍水持续天数等确定了支持作物生长模拟的干旱和渍水胁迫影响因子的算法。用独立于建模的盆栽小麦水分试验观测资料对干旱和渍水胁迫影响因子的算法进     

Genetic parameters for agronomic traits of triticale and other small-grain cereals grown on aluminium-toxic soil in southern Brazil

Aluminium (Al) toxicity is a major limiting factor for plant production on acid soils. Breeding of adapted genotypes presents an alternative to corrective lime application. This study estimated genetic and non‐genetic components of variation, heritabilities, and trait correlations for 20 triticale (×Triticosecale Wittmack) genotypes grown for 2 years on naturally acidic, Al‐toxic (pH 4.4) and lime‐amended soils (pH 5.0 and 6.3). Eight traits were assessed. A 51% mean reduction in grain yield as a result of soil acidity was due to 27% fewer grains/spike, 11% fewer spikes/m² and 7% reduced 1000‐grain weight. Genotypes were the most important source of variation for nearly all traits in the combined analysis across years. Genotype × lime interaction was relevant only for certain traits in a particular year. Despite a substantial genotype × year interaction, the general ranking of genotypes for acid‐soil tolerance did not change across years. Genotypic variation was higher on acidic than on lime‐amended soil. Heritability estimates were similar at the two extreme pH levels. Results suggest that in triticale a wide variation for adaptation to soil acidity exists. Selection under stress appears more effective than under optimal conditions. A visual plant‐development‐stress‐symptom rating can be used to select indirectly for grain yield in a breeding programme.     

土壤水分对长柄扁桃生长特性及蒸散发的影响

以1年生长柄扁桃幼苗为材料,通过盆栽控水试验的方法,设置土壤含水量分别为田间持水量的50%~75%（轻度干旱胁迫）、75%~100%（对照）和100%~125%（水涝胁迫）,研究不同土壤水分胁迫对长柄扁桃幼苗生长特性及蒸散耗水规律的影响。结果表明,水分胁迫对长柄扁桃幼苗生长及蒸散耗水具有明显影响,长柄扁桃蒸散耗水量随水分胁迫程度的加剧呈下降趋势。轻度水分胁迫有利于长柄扁桃株高、基径、叶面积及新枝数的生长,但叶片衰老较快。水涝胁迫在一定程度上有利于长柄扁桃叶面积及基径的生长并能减缓叶片衰老,但不利于株高及新枝数的增加。综合分析认为,轻度水分胁迫是长柄扁桃幼苗生长的适宜土壤水分含量。     

In vitro screening and field evaluation of tissue-culture-regenerated sorghum (Sorghum bicolor (L.) Moench) for soil stress tolerance

Summary Sorghum bicolor (L.) Moench is generally quite sensitive to salt and acid (high aluminium) soil stresses, but quite tolerant of drought stress. As with any stress phenomenon, intra-specific variability exists within the genus. In vitro cell selection and somaclonal variation offer an alternative to traditional breeding methodology for generating improved breeding lines for hybrid development. A field selection protocol was developed for the three soil stresses and inter-stress evaluations were conducted in an effort to find multiple, stress-tolerant genotypes. The acid soil-drought stress, super-tolerant selections were located by the R₇ generation when exposed to a combined aluminium-drought stress field environment and when the regeneration population (number of regenerated lines from one callus source) was maintained at 15,000 plants or higher. A variant frequency of 0.1 to 0.2% for stress tolerance and acceptable agronomic traits among the surviving somaclones, provided an adequate number of phenotypes with desirable agronomic characteristics and a high level of soil stress tolerance. Subsequent research verified that the stress-tolerant regenerants had superior acid soil and drought stress tolerance to that of the donor parents, that their yield capabilities under stress were superior to their parents, and that their stress tolerance attributes were transferred in hybrid combinations. In vitro selection was not effective in increasing the number of field stress survivors. In fact, superior germplasms were developed from non-stressed callus or salt-stressed callus. In vitro selection reduced regeneration frequency and subsequent survival of plants under field stress. In vitro-stressed regenerants should be subjected only to non-stressed environments to maintain population numbers for field selection and thereafter should be subjected to stress environments during later (R₅₊) generations. The optimal strategy for the exploitation of somaclonal variation may be through short-term cell culture (< 12 months) with no attempt at in vitro selection.     

Comparison of yield based drought tolerance indices in improved varieties, genetic stocks and landraces of potato (Solanum tuberosum L.)

Drought strongly influences potato (Solanum tuberosum) production and quality. Potato being a drought susceptible crop, the development of varieties with enhanced tolerance to water stress could highly improve productivity in drought prone areas. The objective of this study was to evaluate the ability of several yield based indices to be used in large scale screening for drought tolerance. The experiment included improved varieties, genetic stocks and landraces potatoes grown under drought and irrigated conditions. A group of accessions with high yield under both conditions was identified. Mean productivity (MP), geometric mean productivity (GMP), tolerance (TOL), drought tolerance index (DTI), drought susceptible index (DSI) and yield stability index (YSI) were calculated from tuber yield under drought and irrigated conditions. The relationships between these indices and yield were analyzed. The Fleiss’ Kappa concordance test was used to analyze the correspondence between accessions previously identified as highly productive under both drought and irrigated conditions and accessions with optimal values for the different indices. MP, GMP and DTI allowed identifying genotypes combining high yield potential and high yield under drought within the three subsets of genotypes. Conversely, DSI, YSI and TOL showed low and variable concordance values across subsets, suggesting that their efficiency in screening genotypes highly depends on the nature of the tested genetic material.     

Varietal Differences of Wheat and Triticale to Water Stress

Six wheat ( Triticurn aestivum L.) and ten triticale (x Triticosecale Wittmack) cultivars were screened for water stress tolerance during germination and seedling stages in the laboratory and growth chamber, respectively. Germinating seeds and hydroponically-grown seedlings were subjected to osmotic stresses of –0.3 and –0.6 MPa using polyethylene glycol M. W. 8000. Both species and cultivar differences were found among the tested genotypes for all the parameters analyzed in both germination and seedling tests. Germination stress index was lower for seed exposed to -0.6 MPa than for -0.3 MPa osmotic stress. A significant relationship was found among plant height, fresh weight and dry weight stress indices evaluated during the seedling test. The cultivars that grew taller under stress conditions had greater dry matter accumulation, as well as higher germination and water uptake stress indices indicating the reliability of height to predict cultivar performance under such conditions. The cultivars Stacy (wheat) and Eu 14/15 (triticale) had higher dry matter accumulation, higher water uptake and leaf water potential, greater height and better germination under stress conditions than the other cultivars tested. Conversely, the cultivars GA 781014 (wheat) and Am 4147 (triticale) performed poorly with respect to all the parameters analyzed. Based on results from germination and seedling tests, the cultivars Stacy and Eu 14/15 were selected for more stress studies in the greenhouse and field.     

Comparison of Salt and Drought‐Stress Effects on Maize Growth and Yield Formation with Regard to Acid Invertase Activity in the Kernels

The long‐term effects of salt stress (11 dS m^?1) and drought stress (35 % WHC) were investigated for two maize genotypes, focusing on the relation between metabolic changes around the time of pollination and the impact on yield determinants at maturity. The relatively salt‐resistant hybrid Pioneer 3906 and the relatively drought‐resistant hybrid Fabregas were compared. The experiments were conducted in large plastic containers in a vegetation hall in two consecutive years (2011 and 2012). Plant height and leaf area were significantly reduced under both stress conditions. The transpiration rate was only slightly reduced under drought stress; but under salt stress, a significant reduction occurred 40–53 days after sowing. As a significant increase in sucrose concentrations was observed in the salt‐treated maize kernels 2 days after pollination, the availability of assimilates was not limiting and the plants could afford to save water by reduced stomatal opening. Although under both stress conditions the soluble acid invertase activity was reduced 2 days after pollination, concomitantly, an increase in hexose concentrations was observed. Thus, in these experiments, the delivery of hexoses by acid invertase activity did not limit kernel development. Differences in grain yield at maturity between salt and drought stress were most likely caused by salt‐specific effects (Na⁺ toxicity), Fabregas being more affected than Pioneer 3906.     

Evaluation of drought and heat tolerance in wheat based on seedling traits and molecular analysis

Polyethylene glycol and cell membrane stability (CMS) assay were used to evaluate drought and heat tolerance, respectively, among 14 wheat lines based on seedling traits and molecular analysis. Significant variation was evidenced for all the investigated seedling traits. Different levels of heritability and genetic advance were found among the tested traits, indicating whether the trait is controlled by additive or non-additive gene action. Drought caused a significant reduction in root and shoot lengths. However, root/shoot ratio under drought stress was increased. Root length showed a highly significant negative correlation with drought susceptibility index (DSI) under drought conditions. Cluster analysis based on seedling traits separated lines mainly by DSI and CMS. Some lines showed drought and heat tolerance by exhibiting a low DSI with high CMS. Sequence-related amplified polymorphism (SRAP) generated a total of 135 bands, with a level of polymorphism ranging from 30 to 86% among the tested lines. SRAP showed its efficiency in discriminating wheat genotypes by gathering all high-DSIlines in one sub-cluster and generating 10 and 3 unique and specific bands for high-DSI-lines and low-DSI-lines, respectively. These bands could be used for further work as SRAP markers associated with drought tolerance in wheat.