Barley mutants with increased tolerance to aluminium toxicity

Acid soil and associated aluminium toxicity are considered as the number one abiotic factor limiting crop production. Over 2 billion hectares of acid soils exist world-wide, both in tropical and moderate climatic zones. In Poland acid soils represent up to60% of arable land. At soil pH < 5.0 Al ions become soluble in water and toxic to plants. Genetic improvement of Al tolerance in crops is the only alternative to soil liming, a traditional but short term and expensive agricultural cure to raise soil pH. Of the various cereals, barley is the most sensitive to Al toxicity. The known sources of Al tolerance in barley are limited to old cultivars and landraces. While they represent multiple alleles of a single locus, there is no potential to improve Al tolerance through recombination of non-allelic additive genes. In the Department of Genetics, Silesian University we have employed induced mutations for rapid creation of variability for Al tolerance in barley. Thirteen mutants with increased levels of tolerance to Al toxicity have been selected in M₃ generation after mutagenic treatment of four barley varieties with N-methyl-N-nitroso urea (MNH) and sodium azide. Six further Al tolerant mutants were identified in the collection of semi-dwarf mutants of the Department. All selected mutants confirmed Al tolerance with the use of three different methods of screening, i.e., root re-growth, root tolerance index and hematoxylin staining. Fourteen mutants exhibited significant root re-growth after 48 hour incubation with 3 ppm Al⁺³ and two of them, namely RL819/2 and RL820/6 were tolerant even to 6 ppm Al⁺³. Crosses of two selected mutants with their respective parent varieties indicated that Al tolerance in each mutant was controlled by a single recessive gene. Out of three methods tested, the root re-growth method facilitated by hematoxylin staining proved to be the most reliable technique for large scale testing. Double treatment with MNH or combined treatment with sodium azide and MNH and 6hinter-incubation germination between treatments were the most successful treatment combinations for induction of aluminium tolerance in barley. This revised version was published online in August 2006 with corrections to the Cover Date.     

Determination of the rate of 18F-labeled water movement to the leaf and its association with water relations in acid soil-tolerant rice varieties

The visual symptoms of damage by acid sulfate soil look quite similar to those due to soil moisture deficit. The present paper is to confirm if acid soil-tolerance is associated with drought tolerance in terms of leaf water potential, transpiration, and dry matter production. Seedlings of seven acid soil-tolerant (acid-tolerant), and three acid soil-intolerant varieties (acid-intolerant) were subjected to low pH conditions (pH 3.8) for 48 hours. The rate of water uptake was determined continuously by measuring radioactivity in the collar part (target area) of rice leaves exposed to ¹⁸F-labeled water (¹⁸F-water) using a Positron Emitting Tracer Imaging System (PETIS). The PETIS measurement showed that the radioactivity in the target position of leaves of acid-tolerant varieties increased faster than that of the intolerant varieties after the ¹⁸F-water was applied into the vial. In the plants subjected to low pH conditions, the transpiration rate (Tr) and leaf water potential (Ψ) decreased in both acid-tolerant and intolerant varieties. However, the extent of reduction was less in the acid-tolerant varieties than in the intolerant ones. Moreover, the dry matter production rate of the acid-tolerant varieties was significantly higher than that of the acid-intolerant ones in the low pH conditions. This study clearly shows that ¹⁸F-water uptake in a leaf was higher, and water relations were also better maintained in the acid-tolerant varieties compared with intolerant ones, resulting in higher growth rate in the acid-tolerant varieties, when plants were exposed to the acid solution conditions. We conclude that acid soil-tolerance is closely associated with leaf water relations in rice plants.     

Assessment of varietal reaction and breeding for resistance to the yellow-dwarf virus in barley

A series of barley varieties of practical interest in Britain and Western Europe were assessed for reaction to the barley yellow-dwarf virus (BYDV). All proved to be highly susceptible. Fourteen barley selections found to be tolerant to BYDV in the United States were also tested. Although all were tolerant to BYDV when tested in the glasshouse, only two were tolerant under British field conditions. One selection was slightly less tolerant of one virus isolate than it was of another isolate.In progeny from crosses of tolerant and susceptible genotypes, the inheritance of BYDV tolerance was conditioned by a single major gene which showed little or no dominance. Results of preliminary work to introduce BYDV tolerance into the new high yielding European commercial barley varieties, using the backcross method, are reported. Following two or three successive generations of backcrossing, the selection of plants containing the tolerance gene in the heterozygous condition became impossible and the homozygous tolerant genotypes had to be reconstituted to facilitate the selection of plants for further breeding.     

Comparative Growth Responses and Ionic Relations of Four Cereals during Salt Stress

Four varieties, one each of triticale, wheat, rye and barley were grown in nutrient solution without and with the addition of 75 and 150 mM NaCl. Plants were exposed to salinity for two weeks and growth and ionic relations of plants were measured. Growth of four cereals varieties was affected to different degrees with salinity and shoot fresh weight/dry weight ratios decreased with increase in salt concentration in root medium. Shoots of barley variety accumulated high content of Na and Cl which were primarily due to higher rates of net ion transport from root to shoot. Higher accumulation of Na and Cl in barley variety shoot accompanied by better relative growth rates indicated plant's ability to compartmentalize ions in vacuoles.     

Antioxidant Activity in Salt‐Stressed Barley Leaves: Evaluating Time‐ and Age‐Dependence and Suitability for the Use as a Biochemical Marker in Breeding Programs

Soil salinity disturbs the equilibrium between reactive oxygen species (ROS) production and removal, leading to a dramatic increase in ROS concentration and oxidative damage. Enzymatic scavenging is one of the two main mechanisms involved in ROS detoxification in plants. This study has investigated the role of major antioxidant (AO) enzymes in mitigating salinity‐induced oxidative stress in plant shoots. Firstly, two barley varieties were used to evaluate the activity of major AO enzymes in different leaves and at different times after salt treatment. Our results showed that AO enzyme activities had strong tissue and time specificity. A further study was conducted using six barley varieties contrasting in salinity tolerance. AO enzyme activities and proline contents were measured in the third leaves of seedlings after plants were treated with 240 mm NaCl for 10 days. No significant correlation was revealed between leaf AO activity and either plant grain yield or plant survival rate under salt stress. In contrast, a significant increase in leaf proline content under salt stress was found in all sensitive varieties, while in most tolerant varieties, salt stress did not change leaf proline level. It is concluded that although salinity induces changes in leaf AO enzyme activities, the changes cannot be used as biochemical indicators in breeding for salinity tolerance.     

盐碱胁迫对不同水稻材料苗期生长特性的影响

【研究目的】为探明水稻苗期耐盐碱特性的生理机制,建立适合江苏滩涂地区简易有效耐盐碱鉴定方法;【方法】以18个不同的粳稻、籼稻以及杂交稻材料作为供试材料,研究人工盐碱处理下,水稻的发芽率、苗高、苗的干物质重以及主根和侧根等生长特性;【结果】研究表明：盐碱处理下,供试水稻品种的生理指标存在显著差异。与粳型水稻材料相比,在盐碱处理下,籼型水稻材料的发芽率低,干物质累积少,主根生长受抑制,而且侧根发根也较少,表现为对盐碱胁迫更为敏感。而杂交稻材料表现则不一致,杂交稻汕优63和两优培九的耐盐碱特性表现处于籼稻和粳稻之间,而杂交稻粤优938的盐碱特性则比籼型水稻材料更为敏感。【结论】经显著性分析,在盐碱处理下,不同水稻品种的发芽率和侧根数目分别在0.01和0.05差异水平,可作为苗期水稻盐碱特性鉴定的重要生理指标。     

大麦耐铝毒机制的研究进展

铝离子对根系的毒害是酸性土壤中农作物生产的主要限制因子。大麦在所有禾本科农作物中对铝离子毒害最为敏感。耐铝毒性在大麦品种间存在变异,遗传分析表明在大麦第4染色体长臂上有一个主效基因（Alp）控制大麦对铝毒的抗性。本文总结了最近几年关于大麦耐铝毒机理的研究进展,特别是大麦耐铝毒基因Alp的克隆及其功能分析,并对禾本科其它农作物中相关耐铝毒基因的研究进行了比较。     

直播早籼稻品种芽期耐冷性鉴定研究

低温胁迫是水稻生产面临的重要非生物胁迫之一,鉴定水稻种质资源芽期耐冷性,筛选耐冷品种对水稻生产具有重要意义。以江西地区主推的33份早籼杂交稻品种和8份常规稻为试验材料,设置12个芽期低温胁迫处理,以死苗率为指标探讨了早籼稻芽期耐冷性的适宜鉴定方法。同时在8℃低温处理10d,恢复生长后调查其成苗率、苗高、根长、根数、地上部生物量、根系生物量和根冠比。运用主成分分析、模糊隶属函数法和聚类分析法来探讨直播早稻芽期的耐冷性评价方法及筛选耐冷品种。结果表明,8℃低温处理10d,直播早籼稻品种死苗率的方差和变异幅度大,能较好地鉴别品种间耐冷性差异,是直播早籼稻芽期耐冷性鉴定的最合理方式;杂交稻品种的耐冷性强于常规稻;低温胁迫后成苗率、苗高、根长、根数、地上部生物量、根系生物量和根冠比基本低于25℃对照处理;利用主成分分析将7个单项指标转化为3个独立的综合指标（CI₁、CI₂、CI₃）,主成分分析表明,根系生物量和地上部生物量最能代表直播早籼稻对低温胁迫后的响应情况,可作为芽期耐冷性鉴定的评价指标。通过聚类分析,将41份早籼稻品种划分为3类,筛选出陵两优7108、两优287、锦两优816等9份强耐冷品种,株两优1号、潭两优83、株两优22等15份中度耐冷品种,温229、中早33、五丰优157等17份冷敏感品种。这些品种可以进一步为耐冷育种和生产服务。     

Morphological and Physiological Studies Concerning the Drought Tolerance of the Secale cereale × Secale montanum Cross Permontra

The root morphology, drought tolerance and heat tolerance of the S. cereale × S. montanum cross Permontra , six cultured S. cereale varieties and the wild rye S. montanum were investigated and the use of membrane stability tests as a selection tool for drought and heat tolerance in rye evaluated.
Root length, surface area and lateral density were measured on plants at the three leaf stage. Tolerance to drought, acute heat and chronic heat stress heat was assessed in culture chamber tests on control and drought or heat conditioned potted plants and membrane stability assessed by measuring electrolytic leakage.
Permontra had the most extensive root system and was the most drought tolerant variety measured. Permontra was also the most tolerant of the varieties to chronic, though not to acute, heat stress. There was no correlation between drought tolerance in potted plants and membrane stability following either heat or dehydration stress.     

Tolerance to high soil acidity in wheat related species,rye and triticale

Summary Several varieties of each of a number of wheat related species and triticale have been tested for tolerance to high soil acidity. The tests were carried out in a laboratory method with a 3:1 mixture of acid soil and peat, to which sulfuric acid is added to create two levels of differentiation for differential tolerance to high soil acidity, the wheat- and barley-differentiating medium resp. It is concluded that the A-genome of Triticum species contributes to tolerance, which becomes manifest in the barley medium only but not in the wheat-differentiating medium. In addition the D-genome attributes to tolerance, differentiating hexaploid wheats from barley, wild and cultivated einkorn and emmer. It is suggested that the contribution of the D-genome in tolerance to high soil acidity, in itself a reflection of soil conditions in the distribution centre of Ae. squarrosa, has in turn attributed to the increased adaptation of hexaploid wheats as compared with tetraploid wild and cultivated wheats. A further contribution to adaptation to adverse soil conditions as found in varieties of triticale might explain partially their ability to be cultivated in areas less well suited for cultivation of breadwheat.     

Differences in Root and Shoot Response to Limited N-supply in Oat and Spring Barley

Oat and spring barley cultivars, varying in origin and date of release, were examined in soil boxes with sloped glass-face. Considerable genotypic differences were found in shoot and root response to high and low nitrogen supply. Oat cultivars, representing a wider germplasm collection, exhibited a stronger and partially different shoot and root response to applied N-levels than barley cultivars. Cultivar-fertilization interaction effects were significant for seminal and adventitious root variation. Genotypic specificity (plasticity) in root response, as revealed in some oat and barley cultivars with a deeper penetration and more vigorous root growth under the low N-supply, was recognized to be a valuable adaptive characteristic for breeding plants on light-textured soils.     

Comparison of European with West Asian and North African winter barleys in tolerance to boron toxicity

Three plastic-house experiments were conducted to compare the tolerance of European with West Asian and North African (WANA) winter barleys to boron (B) toxicity. Experiment I screened 24 winter barley entries with diverse origins. Experiment III tested 420 random accessions from seven European and seven WANA countries. Plants were screened in a soil mixed with boric acid (50 mg B/kg) and foliar B-toxicity symptom scores were recorded. Lower scores indicated higher B-toxicity tolerance. In Experiment II, five lines/varieties from each of the European and WANA groups were grown in pots with two soil B levels (0 and 25 mg B/kg). The West Asian landrace barleys had a lower mean B-toxicity symptom score than the European ones. The Syrian landrace variety normally grown in drier areas had a lower score than the Syrian landrace variety grown in wetter areas. Dry weights of the European and WANA groups were not different without adding B, but dry weight under 25 mg B/kg was lower for the European group than the WANA group. European accessions had a higher mean B-toxicity symptom score than the WANA accessions. Iranian and Afghan accessions had the lowest mean scores among countries. These results support the hypothesis that European winter barley varieties and accessions are less tolerant to B toxicity than those WANA accessions and varieties developed from local landraces. The lower B-toxicity tolerance could be a factor adversely affecting the performance of European winter barley varieties in the highlands of WANA. This revised version was published online in July 2006 with corrections to the Cover Date.     

Identification and crop performance of acid sulfate soil-tolerant rice varieties

The present study aims to: 1) identify acid sulfate soil (ASS)-tolerant rice varieties from the genetic stock of Korean rice (Oryza sativa L.) varieties under ASS conditions; 2) to evaluate their yield performance, and elucidate the physiological mechanism for ASS tolerance with the identified tolerant varieties. Two hundred sixty-six rice varieties were screened for ASS tolerance, and we identified two japonica-indica hybrid varieties, Geumgang (GG) and Pungsan (PS), as having high tolerance under ASS paddy conditions (pH 3). We first conducted a yield trial of GG and PS grown in Wagner pots to determine their potential yields under ASS conditions. A yield trial under paddy field condition followed. In the pot experiment, the ASS-tolerant varieties, GG and PS, showed significantly higher yields than PT-1, which is a local reference variety in mildly improved soil pH conditions (pH 4.1–4.6). Al and Fe content in GG and PS were significantly lower than that of PT-1, so there might be some mechanism that inhibits the absorption of toxic metal ions in the tolerant varieties. In the paddy conditions, the grain yields more than 5 t ha⁻¹ of the two tolerant varieties under mildly improved soil pH condition were significantly higher than PT-1. Dry matter weights of above ground parts also showed the same trend as grain yield. The study demonstrated that the ASS-tolerant japonica-indica rice varieties with high yielding potential could contribute to the improvement of rice yield in ASS regions, and will be good materials for the development of acid soil-tolerant rice varieties.     

Screening soya beans [Glycine max (L.) Merill] for calcium efficiency by root growth in low-Ca nutrient solution

There are severe soil constraints for agriculture in many tropical regions of the world. Acidity and low levels of calcium are examples of them in the Brazilian Cerrados (Savannahs). They may prevent deep root growth of cultivated plants, exposing them to moisture stress during dry spells. This study aimed to develop a technique for screening soya bean varieties tolerant to low calcium based on root growth in nutrient solution. The results have shown varietal differences for tolerance to low-Ca stress. The method of screening for response to low-Ca is quick, non-destructive and can be employed in genetic studies and breeding programmes for efficient calcium utilisation by soya beans. It is expected that improved varieties for this character will lead to yield stability and contribute to develop sustainable farming systems in the savannahs. This revised version was published online in July 2006 with corrections to the Cover Date.     

Selection of young barley plants for tolerance to high soil acidity in relation with some agronomic characteristics of mature plants

Summary In four segregating populations of barley, grown in a naturally highly acid soil good plants and less vigorous ones were marked in a 3–4 leaf stage of development.Some agronomic characters of mature plants were studied in relation with the level of tolerance to high soil acidity of their progenies when tested in a seedling stage in a laboratory method.As compared with the good groups the reductions proved highly significant viz. 60% for mean number of tillers per plant, 25% for average culm length, 35% for mean number of kernels per spike and about 12% for 1000-grain weight.On the average more than 95% of the good plants showed a high level of tolerance to high soil acidity, indicating a close correlation between low-pH tolerance and agronomic performance.Although a rather high percentage (40%) of the progenies among the plants marked as bad was found to be tolerant, those lines showed a poor general performance.This goes to show that selection for tolerance to high soil acidity before flowering is an advisable procedure, without the risk of including sensitive lines or losing otherwise valuable genotypes.This study was carried out during a fellowship of the Spanish Ministry of Agriculture.     

Fungal Endophytes Enhance Agronomically Important Traits in Severely Drought‐Stressed Barley

Crops often face severe and damaging local drought events, and in some regions, these episodes are predicted to become more frequent due to climate change. Some micro‐organisms have been shown to improve drought tolerance and improve yield in crop plants. Here, we show that fungal root endophytes isolated from a wild barley species (Hordeum murinum subsp. murinum) induced significant improvements in agronomic traits for a severely drought‐stressed barley cultivar grown in a controlled environment, including number of tillers, grain yield and shoot biomass. Five endophyte strains were tested, and the trait that showed the greatest significant difference in the drought‐stressed plants was the number of tillers, where all of the endophyte treatments induced a greater number of tillers per plant. However, except in one case, the mean dry root weight for all plants was greater in the control plants, indicating preferential allocation of resources to aboveground parts in the endophyte treatments. Results were not consistent across all endophyte treatments, with some endophytes performing much better than others. As these growth studies were conducted using soil‐based compost, the results may translate to the field and suggest that some of these endophytes have potential as barley inoculants in arid growing conditions.     

Multivariate analysis of traits determining adaptation in cultivated barley

Thirty‐nine barley varieties of different origin, representing different growth types, were included in a series of experiments aimed at analysing the variability in vernalization response, photoperiod sensitivity and earliness per se and establishing the types of ecoclimatic adaptability using multivariate analysis. In the case of spring barley varieties there was no correlation between any of the three traits. For winter barleys, a negative correlation was found between photoperiod sensitivity and vernalization response and between photoperiod sensitivity and earliness per se. Vernalization response and earliness per se showed a positive correlation. Among the winter barley varieties large variations were apparent in photoperiod sensitivity, vernalization response and earliness per se, which resulted in a tremendous variation in flowering patterns and frost tolerance. Between the spring barley varieties only wider variations in photoperiod sensitivity were detected. Based on the cluster analysis, the 39 varieties could be separated into seven groups. The spring barley varieties were placed in two groups, and the winter barleys in five groups representing different adaptational types. Among these five groups two represented the two opposing extreme combinations of photoperiod sensitivity and vernalization response. The combination of large photoperiod sensitivity and no vernalization response resulted in better frost tolerance than did the combination of photoperiod insensitivity and large vernalization response.     

外源水杨酸对NaCl胁迫下黄瓜种子萌发和幼苗根系生长的影响

为了研究外源水杨酸(Salicylic acid,SA)对NaCl胁迫下黄瓜(Cucumis sativus L.)种子萌发特性和幼苗根系生长的影响,以2个黄瓜品种（‘津春五号’、‘世纪春秀’）为材料,以浓度(150 mmol/L)的NaCl溶液结合外源水杨酸SA(0~1.0 mmol/L)处理黄瓜种子并进行发芽试验,观察了黄瓜种子的发芽情况及幼根生长特性。结果表明：在150 mmol/L NaCl胁迫下,黄瓜种子发芽和幼苗根系生长均受到抑制,对黄瓜幼苗根伸长的抑制比茎更明显;外源SA能显著改善NaCl胁迫下黄瓜种子发芽特性,促进幼苗根系的生长,缓解盐胁迫对黄瓜发芽和根系生长的伤害,并以0.25 mmol/L的SA溶液处理对盐胁迫伤害的缓解效果最好。NaCl胁迫下不同品种的耐盐性和外源SA的缓解效应存在差异,‘津春五号’的耐盐性和外源SA的缓解效应高于‘世纪春秀’品种。     

Effect of terminal water stress on leaf epicuticular wax load,residual transpiration and grain yield in barley

The effect of drought on barley leaf epicuticular wax load (EWL), residual transpiration rates (RTR) and grain yield was examined by subjecting 12 barley genotypes to controlled irrigation and terminal water stress conditions. The mean leaf epicuticular wax load was found to be 9% greater in the plants subjected to terminal water stress than in those provided irrigation, while the mean residual transpiration rate of the irrigated plants was 20% higher than in those subjected to water stress. Under these stress conditions, the correlation between grain yield and the epicuticular wax load was positive (P < 0.01), while that between the grain yield and the residual transpiration rate was negative (P < 0.05). Under the water stress conditions, the breeding lines studied showed a greater mean epicuticular wax load than the commercial varieties, while the residual transpiration rate was greater in these varieties than in the breeding lines. The greater epicuticular wax load of the breeding lines favoured their tolerance of drought, improving their yields over those of the commercial varieties.