Quality traits. Semolina Color
References
1. Spectrophotometric determination of yellow pigment content and evaluation of carotenoids by high-performance liquid chromatography in durum wheat grain. Hentschel V, Kranl K, Hollmann J, Lindhauer MG, Bohm V, Bitsch R. In: Journal of Agricultural & Food Chemistry, 2002, 50(23):6663-6668.
The so-called "yellow pigment" content of durum wheat has been used for a long time as an indicator of the color quality of durum wheat and pasta products. For decades the chemical nature of these pigments has been assigned to carotenoids, mainly to the xanthophyll lutein and its fatty acid esters. The chemical composition of the yellow pigments of eight German durum wheat cultivars was studied. Grains were milled on a laboratory mill. Pigment extraction of millstream fractions was performed according to the optimized ICC standard method 152 procedure, and the chemical composition of the extract was analyzed by isocratic reversed phase high-performance liquid chromatography. all-trans-Lutein ranged from 1.5 to 4 mg kg(-1), and zeaxanthin was found in traces. No lutein esters and carotenes were detected. Surprisingly, the fraction of carotenoids of the complete yellow pigment content amounted to only 30-50% of the yellow pigment quantities, so there are still compounds in durum wheat not yet identified that contribute considerably to the yellow color of the grain extracts. The isolation and chemical identification of those pigments are under investigation.
2. Identification of a microsatellite on chromosome 7B showing a strong linkage with yellow pigment in durum wheat (Triticum turgidum L. var. durum). Elouafi I, Nachit MM, Martin LM, In: Hereditas, 2001, 135(2-3):255-261.
The objective of this study is to identify QTLs linked to yellow pigment content in durum wheat. A durum-dicoccoides genetic linkage map was constructed using 124 microsatellites, 149 amplified fragment length polymorphism (AFLPs), and six seed storage proteins (SSP) in a population of 114 recombinant inbred lines (178). The population has been obtained from a cross between a durum cultivar Omrabi5 and Triticum dicoccoides 600545 and backcrossed to Omrabi5. The map consists of 14-durum chromosomes plus an unknown group; and shows a good synteny to the previously published wheat maps. Yellow pigment was measured in the population in three different locations during 3 seasons. Analysis of QTLs was based on simple and simplified composite interval mapping (SIM and sCIM). Three QTLs for yellow pigment were detected on the chromosomal group 7 (7AL and 7BL telomeres) explaining 62% of the total variation. On 7BL, a major microsatellite (Xgwm 344) explained by itself 53%, whereas on 7AL, the other two QTLs have contributed 13 and 6%. All determined QTLs showed a strong genetic effect and a weak QTL x E effect. The QTLs effect was consistent across all environments and showed a large effect. Consequently, promising QTLs will be used in the marker assisted breeding program to enhance the selection efficiency for yellow pigment.
3. Association of a lipoxygenase locus, Lpx-B1, with variation in lipoxygenase activity in durum wheat seeds. Hessler TG, Thomson MJ, Benscher D, Nachit MM, Sorrells ME. In: Crop Science, 2002, 42(5):1695-1700, 2002.
Lipoxygenases constitute a family of enzymes that catalyze the breakdown of lipids, resulting in products that may have undesirable effects. These enzymes can affect pasta color and cause off-flavors. The purpose of this study was to map the loci associated with lipoxygenase activity in seeds of a durum wheat (Triticum turgidum ssp. durum) population to determine if lipoxygenase activity is associated with flour color. Seed of the parents, Jennah Khetifa and Cham 1, and the recombinant inbred population consisting of 113 progeny lines were used to assay lipoxygenase activity and flour color. A saturated molecular-marker linkage map for this population was previously constructed. Allele specific primers targeting the wheat homolog to barley LoxA were designed, and a fragment length polymorphism resulting from a miniature inverted-repeat transposable element (MITE) insertion in an intron of the durum wheat LoxA homolog allowed mapping of the locus to chromosome 4BS. To measure lipoxygenase activity, spectrophotometric changes were recorded. Chain I had a change in absorbance of 0.284 units of absorbance over I min compared with 0.752 units for Jennah Khetifa. Quantitative trait locus analysis of these data indicated that most of the lipoxygenase activity was associated with the wheat lipoxygenase gene (Lpx) on chromosome 4BS. A quantitative trait locus, for vitreous appearance of seeds also was associated with this locus. Flour color was not correlated with lipoxygenase activity in this population. With this knowledge, marker-assisted selection can be used to select genotypes with lower lipoxygenase activity in durum wheat populations.
4. Mapping components of flour and noodle colour in Australian wheat. Mares DJ, Campbell AW. In: Australian Journal of Agricultural Research, 2001, 52(11-12):1297-1309.
Flour and noodle colour influence the value of wheat (Triticum aestivum L.) and are obvious targets for breeders seeking to improve quality, end-product range, and marketability of wheat. The objective of this investigation was to identify quantitative trait loci (QTLs) associated with flour and noodle colour traits and with individual components of colour. One hundred and sixty-three doubled haploid lines derived from Sunco x Tas man, white-grained, prime hard, and hard wheats adapted to the north-eastern region of Australia were used for the bulk of this study and were supplemented by doubled haploid populations derived from CD87 x Katepwa and Cranbrook x Halberd for comparisons of flour colour. Samples of Sunco x Tasman, together with parental lines, were grown at Narrabri, NSW, in 1998 and 1999 and at Roma, Qld, in 1998 and used for visible light reflectance measurements of flour brightness (CIE L*) and yellowness (CIE b*), and white salted noodle (WSN) and yellow alkaline noodle (YAN) brightness, yellowness, and colour stability. Xanthophyll content and polyphenol oxidase (PPO) activity were measured spectrophotometrically.
No consistent QTLs were identified for flour L* or initial L* of WSN and YAN. Xanthophyll content was very strongly associated with QTLs located on chromosomes 3B and 7A and these QTLs also had a major influence on flour b*, WSN b*, and YAN b*. Noodle brightness at 2, 24, and 48 h and the magnitude of change in noodle L* and b* with time were affected by QTLs on 2D, contributed by Tasman, and, to a lesser degree, 2A. The QTL on 2D was clearly associated with control of grain PPO, an enzyme implicated in darkening of Asian style noodles. QTLs located on 2B, 4B, and 5B and associated with control of grain size or flour protein content also appeared to influence a number of colour traits.
5. Mapping Loci Associated with Flour Colour in Wheat (Triticum Aestivum L.) . Parker GD, Chalmers KJ, Rathjen AJ, Langridge P. In: Theoretical & Applied Genetics, 1998, 97(1-2):238-245.
An RFLP map constructed using 150 single seed descent (SSD) lines from a cross between two hexaploid wheat varieties ('Schomburgk' x 'Yarralinka') was used to identify loci controlling flour colour. Flour colour data were obtained from field trials conducted over two seasons at different sites. The estimated heritability of this trait was calculated as 0.67. Two regions identified in the preliminary analysis on chromosomes 3A and 7A, accounted for 13% and 60% of the genetic variation respectively. A detailed analysis of the major locus on 7A was conducted through fine mapping of AFLP markers identified using bulked segregant analysis (BSA). Seven additional markers were identified by the BSA and mapped to the region of the 7A locus. The applicability of these markers to identify wheat lines with enhanced flour colour is discussed.
6. Development of a STS marker linked to a major locus controlling flour colour in wheat (Triticum aestivum L.). Parker GD, Langridge P. In: Molecular Breeding, 2000, 6(2):169-174.
Flour colour is an important quality trait in the production of bread, noodles and other related end products. Current screening for flour colour in breeding programs requires several grams of flour to be milled. In order to screen large numbers of plants, a rapid PCR-based assay is required. We report here the conversion of a codominant AFLP marker linked to a major locus controlling flour colour in hexaploid wheat, to a sequence tagged site (STS) marker for use in marker-assisted selection (MAS). The two-allelic AFLP bands were cloned and sequenced to allow specific primers to be designed. The primers amplified bands of the expected size in the parental varieties and co-segregated with the original AFLP marker in the mapping population. The primers also amplified alleles of the expected size from the DNA of parental lines of two other related mapping populations. Cultivars that contributed to the pedigree of the original parent 'Schomburgk' used to generate the mapping population were also screened to determine the origin of the 'yellow' allele.
7. AFLP and STS tagging of Lr19, a gene conferring resistance to leaf rust in wheat Prins R, Groenewald JZ, Marais GF, Snape JW, Koebner RMD. In: Theoretical & Applied Genetics, 2001, 103(4):618-624.
Amplified fragment length polymorphism (A-FLP) markers were used to enrich the map of the wheat chromosomal region containing the Thinopyrum-derived Lr19 leaf rust resistance gene. The region closest to Lr19 was targeted through the use of deletion and recombinant lines of the translocated segment. One of the AFLP bands thus identified was converted into a sequence-tagged-site (STS) marker. This assay generated a 130-bp PCR fragment in all Lr19-carrying lines tested, except for one deletion mutant, while non-carrier template failed to amplify any product. This sequence represents the first marker to map on the distal side of Lr19 on chromosome 7el(1). The conversion process of AFLP fragments to STS markers was technically difficult, mainly because of the presence of contaminating fragments. Various approaches were taken to reduce the frequency of false positives and to identify the correct clone. We were able to formulate a general verification strategy prior to clone sequencing. Various other factors causing problems with converting AFLP bands to an STS assays are also discussed.
8. Occurrence and impact of a new leaf rust race on durum wheat in northwestern Mexico from 2001 to 2003. Singh RP, Huerta-Espino J, Pfeiffer W, Figueroa-Lopez P In: Plant Disease, 2004, 88:703-–708.
Durum wheat (Triticum turgidum var. durum) is the main irrigated winter crop in northwestern Mexico. Historically, leaf rust, caused by Puccinia triticina, had not induced significant losses to durum production in the area until 2001. That year, a new race, designated as BBG/BN, was detected that caused the most widely grown cultivar, Altar C84, which had remained resistant for 16 years, to become susceptible. Other recommended cultivars also became either moderately susceptible or susceptible. Detailed characterization of avirulence/virulence characteristics on Lr genes indicated that this race possibly did not evolve from the older races, but may have been introduced. Rust epidemics during the 2000-–2001, 2001-–2002, and 2002-–2003 crop seasons have caused estimated losses of at least US$32 million. Although a majority of cultivars from 31 different countries, including the United States and Canada, and most of CIMMYT's durum wheat germ plasm were highly susceptible, diversity for both race-specific resistance and moderate levels of slow rusting resistance were identified. Jupare C2001, a resistant cultivar released in 2001, showed high levels of resistance and negligible losses in grain yield in a trial where Altar C84 suffered over 27% losses. Additional keywords: brown rust.
9. First report of virulence to wheat with leaf rust resistance gene Lr19 in Mexico Huerta-Espino J, Singh RP. In: Plant Disease, 1994, 78:640.
10. Molecular characterization of durum and common wheat recombinant lines carrying leaf rust resistance (Lr19) and yellow pigment (Y) genes from Lophopyrum ponticum. Zhang W, Soria MA, Goyal S, Dubcovsky J, Lukaszewski AJ, Kolmer J. In: Theoretical and Applied Genetics, 2005, 111: 573-582. On-line link: http://dx.doi.org/10.1007/s00122-005-2048-y
Chromosome 7E from Lophopyrum ponticum carries a valuable leaf rust resistant gene designated Lr19. This gene has not been widely used in common wheat breeding because of linkage with the yellow pigment gene Y. This gene tints flour yellow, reducing its appeal in bread making. However, a high level of yellow pigment is desirable in durum wheat breeding. We produced 97 recombinant chromosomes between L. ponticum transfer 7D.7E#1 and its wheat homoeologues, using the ph1b mutation that promotes homoeologous pairing. We characterized a subset of 37 of these lines with 11 molecular markers and evaluated their resistance to leaf rust and the abundance of yellow pigment. The Lr19 gene was mapped between loci Xwg420 and Xmwg2062, whereas Y was mapped distal to Xpsr687, the most distal marker on the long arm of chromosome 7. A short terminal 7EL segment translocated to 7A, including Lr19 and Y (line 1-23), has been transferred to durum wheat by backcrossing. The presence of this alien segment significantly increased the abundance of yellow pigment. The Lr19 also conferred resistance to a new durum leaf rust race from California and Mexico that is virulent on most durum wheat cultivars. The new durum lines with the recombinant 7E segment will be useful parents to increase yellow pigment and leaf rust resistance in durum wheat breeding programs. For the common wheat breeding programs, we selected the recombinant line 1-96, which has an interstitial 7E segment carrying Lr19 but not Y. This recombinant line can be used to improve leaf rust resistance without affecting flour color. The 7EL/7DL 1-96 recombinant chromosome did not show the meiotic self-elimination previously reported for a 7EL/7BL translocation.