A rapid method for screening barley for aluminium tolerance

Summary A method for rapid screening of large numbers of barley genotypes for aluminium tolerance is described, and the results of a small scale screening of composite cross CC XXX-C given.     

Aluminum tolerance in barley: Methods for screening and genetic analysis

Aluminum (Al) tolerance in roots of two cultivars of barley was studied using hematoxylin staining and root re-growth procedures. This study was performed in two F₂ segregating populations originated from crosses between the tolerant FM-404 and sensitive Harrington cultivars. The F₂ progeny analysed with hematoxylin staining revealed a segregation ratio of 3 tolerant: 1 sensitive, showing that the Al tolerance is controlled by a single gene with complete dominance for tolerance. The root re-growth measures do not confirm the 3:1 ratio. This last result can be explained due to the occurrence of genes that affect root growth rate or to the difficulties found in the evaluation of root re-growth. Barley has a complex root system, which makes it difficult to measure root re-growth after an extended period in nutrient solution. Due to the simplicity, reliability and better precision, the hematoxylin staining is the best procedure to determine the Al tolerance and its inheritance in barley. This revised version was published online in August 2006 with corrections to the Cover Date.     

Tolerance to paraquat is correlated with the traits associated with water stress tolerance in segregating F2 populations of barley and wheat

To identify scorable marker traits that can be used in cereal breeding programs for selecting drought tolerant individuals, we investigated the correlation among the drought-associated traits in two F₂ populations derived from the crosses made between drought tolerant and sensitive barley and wheat parental genotypes. The parental genotypes of these crosses also differed by at least three other traits – paraquat tolerance, leaf size, and the relative water content. These three traits were scored in two F₂populations of 80 individuals for each barley and wheat cross. Analysis of results indicated that the enhanced tolerance to paraquat was correlated with reduced leaf size and increased relative water content, two traits associated with water stress phenotypes of the drought tolerant barley and wheat parents. Our results suggested that the selection based on paraquat tolerance istechnically less demanding and thus useful for rapid screening of individuals for enhanced drought tolerance in segregating populations. This revised version was published online in August 2006 with corrections to the Cover Date.     

Aluminium uptake by roots of rye seedlings of differing tolerance to aluminium toxicity

Summary The aluminium accumulation pattern was studied in roots and root tips of rye seedlings from two inbred lines, differing in Al-tolerance and their F₁ hybrid.This investigations were undertaken in order to find whether the mechanism preventing root tips from to high Al-accumulation and damage to apical meristem observed in Al-tolerant isoline of wheat is also operating in rye. Al-uptake into the root tissue was studied in nutrient solution experiments during 24 h of incubation in solution containing aluminium. After Al-incubation roots were harvested, separated into root tips and basal parts, and aluminium content in root tissue was determined after wet digestion using catechol violet colorimetric method. It was found, that at low external Al-concentration in rye roots the mechanism preventing root tips from Al-accumulation and Al-damage operates, similarly as in Al-tolerant wheat isoline. But contrary to wheat in rye seedlings functioning of this mechanism was observed in both Al-tolerant and Al-sensitive lines. It is concluded that observed mechanism of the inhibition of Al-accumulation in apical part of roots plays much more important role in Al-tolerance mechanism in wheat than in rye.Abbreviations EDTA ethylenediaminetetraacetic acid - NIL near-isogenic line     

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.     

Studies for assessing the influence of hardening on cold tolerance of barley genotypes

Summary Frost tolerance of 30 barley (Hordeum vulgare L.) cultivars have been field evaluated in North Italy during the 1990/1991 winter season that was characterized by exceptionally low temperatures without snow cover. The results showed a significant correlation between cold injury and grain yield loss (r=0.61^**). Five cultivars chosen for their varying degree of frost tolerance were further evaluated using laboratory tests. Measurements of survival rate and membrane damage were used to assess the influence of hardening on frost resistance. The reliability of the tests is shown by the high correlation to the field data. For both the laboratory temperature regimes and field conditions, the tested cultivars showed the same order of classification. The effect of a rise in temperature at the end of the hardening treatment on frost tolerance is also reported. The laboratory tests here proposed can be integrated in a breeding programme for improving frost tolerance in barley.     

Diallel analysis of tolerance to aluminium in alfalfa

Summary Acid soils having high levels of aluminium (Al) can drastically reduce yields in alfalfa and the most economically viable solution to the problem appears to be the development of Al-tolerant cultivars. To assist with the choice of a breeding method, a six-parent alfalfa diallel (crosses and reciprocals included but not parents) was evaluated in Al-toxic nutrient solution in terms of height (HT) and dry weight (DW). General combining ability was significant for both traits and constituted the majority of the genetic variation. Specific combining ability was significant only for HT and reciprocal effects were significant only for DW. Tolerance appeared to be at least partially dominant to sensitivity. Results indicate that a mass selection scheme, such as recurrent phenotypic selection, may be effective in increasing levels of tolerance in at least some alfalfa populations and that minor grains may also be achieved through exploiting non-additive genetic variation.     

Salt stress tolerance in heterogeneous populations of barley

Summary Four highly heterogeneous populations of barley were assayed for salt stress tolerance at the time of seed germination. Three of these, Davis, Dryland and Irrigated, were derived originally from a population called Composite Cross XXI and propagated until F₁₇ under contrasting conditions. The fourth, Composite Cross XXX-C, was of relatively recent (F₅) origin. This population showed the highest germinability in nutrient solution salinated with sodium chloride. Davis was poorer in salt tolerance than CC XXX-C but better than Dryland and Irrigated. Dryland and Irrigated, propagated for 14 successive genrations under contrasting levels of soil moisture, showed no significant difference in salt stress tolerance. In several hundred random samples of lines developed from these two populations, ear row number, lemma awn texture, seed weight and yield showed non-random associations with salt tolerance. These associations might be gainfully utilized in barley breeding for salt stress tolerance.     

Variation in utilization efficiency and tolerance to reduced water and nitrogen supply among wild and cultivated barleys

Broad genotypic variation in the response to low soilmoisture and reduced nitrogen supply was found amongthe wild Hordeum spontaneum accessions and thelandraces and modern cultivars of H. vulgare ofdifferent geographic origin. Measurements at the endof vegetative growth in plants grown in soil culturesrevealed genotypically specific responses to the usedenvironmental factors. Cultivars and breeding linesfrom Syria and Ethiopian landraces combined bothdrought resistance and tolerance to low nitrogen. TheSyrian barleys were also distinguished by a highnitrogen utilization efficiency (NUE) under low Nnutrition. European cultivars indicated a pooradaptation to N shortage, but some of them wereresistant to soil drought. No stress resistant barleyswere found among the wild accessions and Sardinianlandraces. Genotypic differences in the relativevalues of NUE and water use efficiency were associatedwith low N-tolerance. Some Syrian selections,Ethiopian landraces and the modern German cv. Maresiwere found to be most drought resistant. Maintenanceof a relatively high photosynthetic activity of theuppermost leaves was associated with droughtresistance. As far as concerning with the vegetativegrowth phase, the modern Syrian germplasm andEthiopian landraces may be recommended as donors ofadaptative characters for local barley breeding.     

A proposal for increased research on chemical induction of fertility in genetic male-sterile barley

Summary We propose that research be increased on chemical restoration of fertility to the genetic male steriles of barley. Seed harvested from male-sterile plants restored to fertility can then be planted as the female for hybrid barley production. Male fertility has been resotred in male-sterile or gynoecious plants by chemicals in many species, but a satisfactory method has not been developed in barley. Male-sterile mutants that self and mutant-chemical combinations with fertility persisting into the second generation should be avoided.Published with the approval of the Director of the Montana Agricultural Experiment Station as Journal series No. 753.     

Genotypic differences in wheat Al tolerance

Summary Aluminium tolerance of 83 genotypes from Croatian and Yugoslav Triticum aestivum germplasm was evaluated in nutrient solutions having Al³⁺ activities of 0, 12.5 and 25 M. Relative root length (25 M Al³⁺/0 Al) of various genotypes ranged from 2 to 97% (from very sensitive to tolerant to Al). No genotype with Al tolerance close to that of very tolerant cultivar Atlas-66 was found. Soil, climatic, fertilization, and liming effects that wheat plants giving seeds for the nutrient solution Al-tolerance screening had been subjected to during their growth cycle did not influence the Al-tolerance ranking. Significant correlation was found between screening wheat for Al tolerance in nutrient solutions and in acid Pseudogley soil amended with five rates of limestone in a greenhouse experiment. Seed protein concentration was significantly related to the Al-tolerance ranking (r² = 0.962). Such a significant correlation was not obtained in a case of rheological and other quality characteristics of seeds. Al-tolerant wheat genotypes identified in this study will be used in breeding for improved Al tolerance.Abbreviations HSD Tukey's Honestly Significant Difference - RRL-2 relative root length, in % (12.5 M Al³⁺/0 Al) - RRL-4 relative root length, in % (25 M Al³/0 Al)     

Genetic relationships among cold, salt and drought tolerance during seed germination in an interspecific cross of tomato

Seed of BC₁ progeny of an interspecific cross between a slow germinating Lycopersicon esculentum breeding line(NC84173; maternal and recurrent parent) and a fast germinating L.pimpinellifolium accession (LA722) were evaluated for germination under cold stress, salt stress and drought stress, and in each treatment the most rapidly germinating seeds (first 2%) were selected. Selected individuals were grown to maturity and self-pollinated to produce BC₁S₁ progeny families. The selected BC₁S₁ progeny from each experiment were evaluated for germination rate in each of a non stress (control),cold-, salt- and drought-stress treatment, and their performances were compared with those of a non selected BC₁S₁population in the same treatments. Results indicated that selection for rapid seed germination in each of the three stress treatments was effective and significantly improved progeny germination rate under all three stress conditions. The results support the suggestion that same genes might control the rate of seed germination under cold, salt and drought stress. Furthermore, selection in each of the three stress treatments resulted in improved progeny seed germination rate under nonstress conditions, suggesting that genetic mechanisms that facilitate rapid seed germination under stress conditions might also contribute to rapid germination under nonstress conditions. In practice, therefore, selection for rapid seed germination under a single stress environment may result in progeny with improved seed germination under a wide range of environmental conditions. Furthermore, to improve germination rate under nonstress conditions, it might be more efficient to make selections under stress conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

Analysis of genetic relationships among 22 European barley varieties based on two PCR markers

Two long primers of 19 (F17) and 20 (F13) nucleotides, respectively,were used in polymerase chain reactions to amplify DNA from differentcultivated barley accessions. These primers can distinguish closely relatedvarieties and, with a unique primer, all the barley accessions analysedshowed a characteristic fingerprint. Sixty per cent and 76% of thefragments generated using F13 and F17, respectively, were polymorphic.The genetic similarity values between accessions were estimated from F13and F17 data. The dendrogram and principal coordinate analysis performedwith F13 data revealed a clear separation of these varieties in accord withtheir pedigree relationships.     

Evaluation of barley yellow dwarf tolerance from plant traits in two winter × spring barley crosses

Summary Winter-type experimental lines from crosses of two winter-type barley cultivars with a spring-type, barley yellow dwarf (BYD) tolerant cultivar were compared in inoculated and uninoculated hill plots. Mature plants traits-winter survival, height, number of spike-bearing tillers, and biomass-were examined. The experimental lines could not be compared with the BYD tolerant parent using these diagnostic symptoms since the spring-type parent would be winterkilled. Two criteria were used to rate experimental lines for BYD tolerance: (1) nonsignificant difference between BYD-inoculated and BYD-uninoculated treatments for all traits, and (2) a BYD injury score obtained by averaging percent reduction from BYD infection for each trait.Missouri Agricultural Experiment Station Journal Paper No. 10059. This research supported in part by Anheuser-Busch, Inc, St. Louis, MO, USA.     

Detection of tolerance of barley cultivars to infection by powdery mildew (Erysiphe graminis f.sp. hordei)

Summary Barley genotypes representing a wide range of resistance expressions and origins, from major resistance genes in modern cultivars to field resistances in landraces, were assessed for tolerance to disease under glasshouse and field conditions. A few genotypes were picked out as showing less yield loss than would be expected from the level of mildew infection. Genotypes showing more than the expected yield loss were also found. The potential use of tolerance as a breeding character is discussed.     

Stable resistance in barley to Pyrenophora teres f. teres isolates from the Nordic-Baltic region after increase on standard host genotypes

Results from tests of a mixture of Finnish net blotch, Pyrenophora teres Drechs. f. teres Smedeg., isolates on a differential series of barley seedlings, comprising 17genotypes, indicated that patterns of infection response (IR)and percentage leaf area damaged (PLAD) were unaffected by differences in seedling size. Variation of the concentration of inoculum between 1,250 conidia ml^-1 and 20,000 conidia ml^-1 produced similar patterns of IR and PLAD on the differential series. IR and PLAD scored on the second seedling leaf differentiated resistance to P. teres f. teresamong the genotypes better than on the first seedling leaf. Ina second experiment, 120 single-spore P. teres f. teres isolates from Finland, Sweden, Norway, Latvia, Estonia and Ireland were used in tests conducted in the greenhouse to differentiate them in terms of virulence reaction on seedlings of six differential barley genotypes. Each isolate was tested directly following isolation from the leaf material and after having passaged each through barley cvs. Arve or Pohto, to produce 360 isolates in total. Virulence of the isolates differed significantly on the members of the differential series, but differences associated with country of origin and passaging, and interactions, were small. It is concluded that little variation between virulence of P. teres f. teres isolates is evident over a large geographic area, incorporating Nordic and Baltic countries, and Ireland. Barley genotype response to P. teres f. teres appeared to be of more significance than relative virulence of the pathogen isolates. This could simplify breeding barley for improved resistance to this phytopathogen. This revised version was published online in August 2006 with corrections to the Cover Date.     

Analysis of the yield potential and yield components of F1 and F2 hybrids of crosses between wheat (Triticum aestivum L.) and spelt (Triticum spelta L.)

Summary Crosses of wild barley (Hordeum vulgare ssp. spontaneum and Hordeum vulgare ssp. agriocrithon) with Hordeum vulgare ssp. vulgare were used to select high yielding grain types under dryland Mediterranean conditions. No special difficulties were faced in making the crosses, in eliminating the brittle rachis genes from the grain types or in selecting 6-rowed types in crosses between 2-rowed wild barley and 6-rowed ssp. vulgare varieties. Brittle rachis genotypes, present in the segregating populations were used in developing self-reseeding permanent pastures for dry areas. The best selections were tested in seven trials during 1989–92 and some of them outyielded their parents and also the best improved check variety by 13–22%. Indications for transgressive segregation were obtained for grain yield, straw yield, total biological yield, harvest index and volume weight. The crude protein content of some of the selections was significantly higher than that of the checks. For breeding programs aiming at large seeds, special ssp. spontaneum lines should be used as parents. High grain yield was positively correlated with high straw yield, total biological yield, earliness in heading date, high harvest index and negatively with volume weight. It was concluded that unexploited useful genes, even when not directly observed in wild barley, could be transfered easily into high yielding genotypes by breeding.     

Exploitable genetic variation in a composite bulk population of barley

Summary Advanced agricultures are characterized by a great increase in the adoptation of uniform crop cultivars associated with a drastic reduction in locally adapted variation, the plant breeders should also examine means of creating and conserving genetic resources. Composite cross breeding is a technique that creates and preserves genetic variation in an exploitable form. The merits and problems of this method were discussed. using data obtained from barley Composite Cross XXI.     

Molecular mapping of quantitative trait loci (QTLs) controlling aluminium tolerance in bread wheat

Aluminium (Al) toxicity is a major constraint to crop productivity in acidic soils. A quantitative trait locus (QTL) analysis was performed to identify the genetic basis of Al tolerance in the wheat cultivar ‘Chinese Spring’. A nutrient solution culture approach was undertaken with the root tolerance index (RTI) and hematoxylin staining method as parameters to assess the Al tolerance. Using a set of D genome introgression lines, a major Al tolerance QTL was located on chromosome arm 4DL, explaining 31% of the phenotypic variance present in the population. A doubled haploid population was used to map a second major Al tolerance QTL to chromosome arm 3BL. This major QTL (Qalt _CS .ipk-3B) in ‘Chinese Spring’ accounted for 49% of the phenotypic variation. Linkage of this latter QTL to SSR markers opens the possibility to apply marker-assisted selection (MAS) and pyramiding of this new QTL to improve the Al tolerance of wheat cultivars in breeding programmes.