Envoy at 09:55, 17 July 2007

2007-07-17T09:55:07Z

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[[Image:Triticale.jpg|left|thumb|Triticale]] '''Triticale''' (x ''Triticosecale'') is an artificial or man-made [[hybrid]] of [[rye]] and [[wheat]] first [[plant breeding|bred]] in laboratories during the late [[19th century]]. The grain was originally bred in [[Scotland]] and [[Sweden]]. Commercially available triticale is almost always a 2nd generation hybrid, i.e. a cross between two kinds of triticale (primary triticales). As a rule, triticale combines the high yield potential and good [[grain]] quality of [[wheat]] with the disease and environmental tolerance (including soil conditions) of [[rye]]. Only recently has it been developed into a commercially viable crop. Depending on the [[cultivar]], triticale can more or less resemble either of its parents. It is grown mostly for [[forage]] or animal [[feed]] although some triticale-based foods can be purchased at [[health food]] stores or are to be found in some breakfast [[cereals]].

The word 'triticale' is a [[portmanteau|fusion]] of the [[latin]] words ''triticum'' (or wheat) and ''secale'' (rye). When crossing [[wheat]] and [[rye]], [[wheat]] is used as the female parent and [[rye]] as the male parent (pollen donor). The resulting hybrid is [[infertility|sterile]] and thus has to be treated with the [[alkaloid]] chemical [[colchicine]] to make it fertile and thus able to reproduce itself.

{{Agricultural production box
|plant=Triticale
|year=2005
|country1={{POL}}
|amount1=3.7
|country2={{GER}}
|amount2=2.7
|country3={{FRA}}
|amount3=1.8
|country4={{CHN}}
|amount4=1.3
|country5={{BEL}}
|amount5=1.1
|country6={{AUS}}
|amount6=0.6
|country7={{HUN}}
|amount7=0.6
|country8={{CZE}}
|amount8=0.3
|country9={{SWE}}
|amount9=0.3
|country10={{DEN}}
|amount10=0.2
|world=13.5
}}

The primary producers of triticale are [[Germany]], [[France]], [[Poland]], [[Australia]], [[China]] and [[Belarus]]. In 2005, according to the [[Food and Agriculture Organization]] (FAO), 13.5 million tons were harvested in 28 countries across the world.

The triticale hybrids are all [[amphidiploid]], which means the plant is [[diploid]] for two [[genomes]] derived from different [[species]], in other words triticale is an [[allotetraploid]]. In earlier years most work was done on octoploid triticale. Different [[ploidy]] levels have been created and evaluated over time. The tetraploids showed little promise, but hexaploid triticale was successful enough to find commercial application. (Oetler 2005)

The [[CIMMYT]] triticale improvement program wanted to improve food production and nutrition in [[developing countries]]. According to Villegas (1973) triticale has potential in the production of bread and other food products such as [[pasta]] and breakfast [[cereals]]. The [[protein]] content is higher than that of [[wheat]] although the [[glutenin]] fraction is less. Assuming increased acceptance, the [[milling]] industry will have to adapt to triticale, as [[milling]] techniques used for [[wheat]] don't suit triticale. Sell ''et al.'' (1962) delivered reports of triticale suitability as a [[grain]] [[feed]] and it is a better [[ruminant]] [[feed]] than other [[cereals]] due to its high [[starch]] digestibility. (Bird ''et al.'' 1999) As a [[feed]] [[grain]] triticale is already well established and of high economic importance. Triticale has received attention as a potential [[energy crop]] and research is currently being conducted on the use of the crops [[biomass]] in [[bioethanol]] production.

==Biology and genetics==
[[Image:Wheat ry triticale.JPG|280px|right|thumb|The grain of [[wheat]], [[rye]] and triticale - triticale [[grain]] is significantly larger than that of [[wheat]].]]
Earlier work with [[wheat]]-[[rye]] crosses was difficult due to low survival of the resulting hybrid [[embryo]] and spontaneous [[chromosome]] doubling. (Oetler, 2005). These two factors were difficult to predict and control. It was necessary to find ways to alter or control these factors. To improve the viability of the [[embryo]] and thus avoid its abortion, [[in vitro]] culture techniques were developed. (Laibach, 925) [[Colchicine]] was used as a chemical agent to double the [[chromosomes]]. (Blakeslee & Avery 1937) After these developments a new era of triticale [[breeding]] was introduced. Earlier triticale hybrids had four reproductive disorders namely, [[meiotic]] instability, high [[aneuploid]] frequency, low [[fertility]] and shriveled [[seed]]. (Muntzing 1939; Krolow 1966). Cytogenetical studies were encouraged and well funded to overcome these problems.

It is especially difficult to see the expression of [[rye]] [[genes]] in the background of [[wheat]] [[cytoplasm]] and the predominant [[wheat]] nuclear [[genome]]. This makes it difficult to realise the potential of [[rye]] in disease resistance and ecological adaptation. One of the ways to relieve this problem was to produce secalotricum in which [[rye]] [[cytoplasm]] was used instead of that from [[wheat]].

Triticale is essentially a self-fertilizing (naturally [[inbred]]) crop. This mode of reproduction results in a more [[homozygous]] [[genome]]. The crop is however adapted to this form of reproduction from an evolutionary point of view. Cross-fertilization is also possible, but it is not the primary form of reproduction.

==Conventional breeding approaches==

The aim of a triticale [[breeding]] programme mainly focuses on the improvement of quantitative [[traits]] such as [[grain]] yield, nutritional quality, plant height, as well as [[traits]] which are more difficult to improve such as earlier maturity and improved test weight. (A measure of yield) These [[traits]] are controlled by more than one [[gene]]. (Triticale Production and Utilization Manual 2005) However, problems arise because such [[polygenic]] [[traits]] involve the integration of several physiological processes in their expression. Thus the lack of single-[[gene]] control (or simple inheritance) results in low [[trait]] heritability. (Zumelzú ''et al.'' 1998)

Since the induction of the [[CIMMYT]] triticale [[breeding]] programme in 1964, improvement in realized [[grain]] yield has been remarkable. In 1968, at Ciudad Obregon, Sonora State in Northwest [[Mexico]], the highest yielding triticale line produced 2.4 t/ha. Today, [[CIMMYT]] has released high yielding spring triticale lines (e.g. Pollmer-2) which have surpassed the 10 t/ha yield barrier under optimum production conditions. (Hede 2000)

Based on the commercial success of other hybrid crops, the use of hybrid triticales as a strategy for enhancing yield in favourable as well as marginal environments has proven successful over time. Earlier research conducted by [[CIMMYT]] made use of a chemical hybridising agent in order to evaluate [[heterosis]] in [[hexaploid]] triticale hybrids. To select the most promising parents for hybrid production, testcrosses conducted in various environments are required. This is because the variance of their specific combining ability (sca) under differing environmental conditions is the most important component in evaluating their potential as parents to produce promising hybrids. The prediction of general combining ability (gca) of any triticale plant from the performance of its parents is only moderate with respect to [[grain]] yield. Commercially exploitable yield advantages of hybrid triticale [[cultivars]] is dependent on improving parent [[heterosis]] and on advances in [[inbred]]-line development.

Triticale is useful as an animal [[feed]] [[grain]]. However, it is necessary to improve its [[milling]] and bread-making quality aspects in order to increase its potential for human consumption. It was initially noted that the relationship between the constituent [[wheat]] and [[rye]] [[genomes]] produced meiotic irregularities and that [[genome]] instability and incompatibility presented numerous problems when attempts were made to improve triticale. This led to two alternative methods to study and improve the crops reproductive performance, namely the improvement of the number of [[grains]] per floral spi
kelet and its meiotic behaviour. The number of [[grains]] per spikelet has an associated low [[heritability]] value. [de Zumelzú et al. 1998] In improving yield, indirect selection (the selection of correlated/related [[traits]] other than that to be improved) is not necessarily as effective as direct selection. (Gallais 1984)

Lodging (the toppling over of the plant stem especially under windy conditions) resistance is a complexly inherited (expression is controlled by many [[genes]]) [[trait]] and has thus been an important [[breeding]] aim in the past. (Tikhnenko ''et al.'' 2002) The use of dwarfing [[genes]] (known as ''Rht'' [[genes]]) which have been incorporated from both ''Triticum'' and ''Secale'' has resulted in a decrease of up to 20cm in plant height without causing any adverse side effects.

==Application of newer techniques==

Abundant information exists concerning disease resistance (R) [[genes]] for [[wheat]] and a continuously updated on-line catalogue (Catalogue of Gene Symbols) of these [[genes]] can be found at http://wheat.pw.usda.gov/ggpages/wgc/98/. Another on-line database of [[cereal]] rust resistance [[genes]] is available at http://www.cdl.umn.edu/res_gene/res_gene.html. Unfortunately less is known about [[rye]] and particularly triticale R-[[genes]]. Many R-[[genes]] have been transferred to [[wheat]] from its wild relatives and appear in the catalogue and are thus available to triticale [[breeding]]. The two mentioned databases are significant contributors to improving the genetic variability of the triticale [[gene pool]] through [[gene]] (or more specifically, allele) provision. Genetic variability is essential for progress in [[breeding]]. In addition, genetic variability can also be achieved by producing new primary triticales (i.e. the reconstitution of triticale), the development of various hybrids involving triticale such as triticale-[[rye]] hybrids. In this way some [[chromosomes]] from the R [[genome]] have been replaced by some from the D [[genome]]. The resulting so-called substitution and translocation triticale facilitates the transfer of R-[[genes]].

===Introgression===
Introgression involves the crossing of closely related plant relatives and results in the transfer of ‘blocks’ of [[genes]], i.e. larger segments of [[chromosomes]] compared to single [[genes]]. R-[[genes]] are generally introduced within such blocks, which are usually incorporated/translocated/introgressed into the distal (extreme) regions of [[chromosomes]] of the crop being introgressed. [[Genes]] located in the proximal areas of [[chromosomes]] may be completely linked (very closely spaced) thus preventing or severely hampering [[genetic recombination]] which is necessary to incorporate such blocks. (Chelkowski & Tyrka 2004) Molecular markers (small lengths of [[DNA]] of a characterized/known sequence) are used to ‘tag’ and thus track such translocations. A weak [[colchicine]] chemical solution has been employed to increase the probability of [[recombination]] in the proximal [[chromosome]] regions and thus the introduction of the translocation to that region. The resultant translocation of smaller blocks that indeed carry the R-[[gene]]/s of interest has decreased the probability of introducing unwanted [[genes]]. (Lukaszewski 1995)

===Production of doubled haploids===
Doubled [[haploid]] (DH) plants have the potential to save much time in the development of [[inbred]] lines. This is achieved in a single generation as opposed to many which would otherwise occupy much physical space/facilities. DHs also express deleterious recessive [[alleles]] that are otherwise masked by dominance effects in a [[genome]] containing more than one copy of each [[chromosome]]. (And thus more than one copy of each [[gene]]) Various techniques exist to create DHs. The [[in-vitro]] culture of [[anthers]] and [[microspore]]s is most often used in [[cereals]] including triticale. (Bernard & Charmet 1984; González and Jouve 2000; González ''et al.'' 1997) These two techniques are referred to as androgenesis, which ref
ers to the development of [[pollen]]. Many plant species and [[cultivars]] within species including triticale are recalcitrant in that the success rate of achieving whole newly generated (diploid) plants is very low. GenotypeXculture medium interaction is responsible for varying success rates, as is a high degree of [[microspore]] abortion during culturing. (Gonzalez & Jouve 2005; Johansson ''et al.'' 2000) It is known that the response of parental triticale lines to [[anther]] culture is correlated (related) to the response of their progeny. (Anderson ''et al.'' 1989; Gonzalez ''et al.'' 1997; Konzak & Zhou 1992)

[[Chromosome]] elimination is another method of producing DHs and involves [[hybrid|hybridisation]] of [[wheat]] with [[maize]] (''Zea mays'' L.) followed by [[auxin]] treatment and the artificial rescue of the resultant [[haploid]] [[embryos]] before they naturally abort. This technique is applied rather extensively to [[wheat]]. (Bennet ''et al.'' 1990) Its success is in large part due to the insensitivity of [[maize]] [[pollen]] to the crossability inhibitor [[genes]] known as Kr1 and Kr2 that are expressed in the floral [[style]] of many [[wheat]] [[cultivars]]. (Bennett & Laurie 1987) The technique is unfortunately less successful in triticale. (Marcinska ''et al.'' 1998) However, ''[[Imperata cylindrica]]'' (a grass) was found to be just as effective as [[maize]] with respect to the production of DHs in both [[wheat]] and triticale. (Chaudhary ''et al.'' 2005)

===Application of molecular markers===
An important advantage of [[biotechnology]] applied to plant [[breeding]] is the speeding up of [[cultivar]] release that would otherwise take 8-12 years. It is the process of [[selection]] that is actually enhanced, i.e. retaining that which is desirable or promising and ridding that which is not. This carries with it the aim of changing the [[Genetics|genetic]] structure of the plant population. The website http://maswheat.ucdavis.edu/protocols/protocols.htm is a valuable resource for [[MAS]] (Marker Assisted [[Selection]]) protocols relating to R-[[genes]] in [[wheat]]. MAS is a form of indirect [[selection]]. The Catalogue of [[Gene]] Symbols mentioned earlier is an additional source of [[molecular]] and morphological markers. Again, triticale has not been well characterized with respect to [[molecular]] markers although an abundance of [[rye]] [[molecular]] markers makes it possible to track [[rye]] [[chromosomes]] and segments thereof within a triticale background.

Yield improvements of up to 20% have been achieved in hybrid triticale [[cultivars]] due to a phenomenon described as [[heterosis]]. (Becker ''et al.'' 2001; Burger ''et al.'' 2003; Góral 2002; Góral ''et al.'' 1999) This raises the question of what [[inbred]] lines should be crossed (to produce hybrids) with each other as parents in order to maximize yield in their hybrid progeny. This is termed the ‘combining ability’ of the parental lines. The identification of good combining ability at an early stage in the [[breeding]] program can reduce the costs associated with ‘carrying’ a large number of plants (literally thousands) through the program and thus forms part of efficient [[selection]]. Combining ability is assessed by taking into consideration all available information on [[descent]] ([[Genetics|genetic]] relatedness), [[Morphology (biology)|morphology]], qualitative (simply inherited) [[traits]] and [[biochemical]] and [[molecular]] markers. There exists exceptionally little information on the use of [[molecular]] markers to predict [[heterosis]] in triticale. (Góral ''et al.'' 2005) It is generally accepted that [[molecular]] markers are better predictors than morphological markers ([[agronomy|agronomic]] [[traits]]) due to their insensitivity to variation in environmental conditions.

A useful [[molecular]] marker known as a SSR (Simple Sequence Repeat) is used in [[breeding]] with respect to [[selection]]. SSRs are [[DNA]] fragments containing tandem repeats of a short sequence of [[nucleotides]], actually 2–6. They are popular tools in [[genetics]] and [[breeding]] because of their relative abundance compared to other [[molecular]] marker types, high degree of polymorphism (number of variants) and easy assaying through co-dominance and PCR. ([[Polymerase Chain Reaction]]) However, they are expensive to develop/identify. Comparative [[genome]] mapping has revealed a high degree of similarity in terms of sequence co-linearity between closely related crop [[species]]. This allows the exchange of such markers within a group of related [[species]] such as [[wheat]], [[rye]] and triticale. One study established a 58% and 39% transferability rate to triticale from [[wheat]] and [[rye]] respectively. (Baenziger ''et al.'' 2004) ‘Transferability’ refers to the phenomenon where the sequence of [[DNA]] [[nucleotides]] flanking the SSR loci (position on the [[chromosome]]) is sufficiently homologous (similar) between [[genomes]] of closely related [[species]]. Thus [[DNA]] primers (a generally short sequence of [[nucleotides]] literally used to ‘prime’ a copying reaction during PCR) designed for one [[species]] can be used to detect SSRs in related [[species]]. SSR markers are available in [[wheat]] and [[rye]] but very few if any are available for triticale. (Baenziger ''et al.'' 2004)

===Genetic transformation===
The [[genetic transformation]] of crops involves the incorporation of ‘foreign’ [[genes]] or rather, very small [[DNA]] fragments compared to introgression discussed earlier. Amongst other uses [[genetic transformation|transformation]] is a useful tool to introduce new [[traits]]/characteristics into the transformed crop. Two methods are commonly employed, i.e infectious [[bacteria]] ([[Agrobacterium]]) -mediated and [[biolistics]] with the last-mentioned being most commonly applied to [[allopolyploid]] [[cereals]] such as triticale. [[Agrobacterium]]-mediated [[genetic transformation|transformation]] however holds several advantages such as a low level of [[transgenic]] [[DNA]] rearrangement, low number of introduced copies of the transforming [[DNA]], stable integration of a priory characterized T-[[DNA]] fragment (containing the [[DNA]] expressing the [[trait]] of interest) and an expected higher level of [[transgene]] expression. Triticale has until recently only been transformed via [[biolistics]] with a 3.3% success rate. (Becker ''et al.'' 1995) Little has been documented on [[Agrobacterium]]-mediated transformation of [[wheat]] while nothing exists with respect to triticale until a recent study by Binka ''et al.'' (2005) in which the success rate was nevertheless low.

==Conclusion==

Triticale holds much promise as a commercial crop as it goes a long way toward addressing specific problems within the [[cereal]] industry. Research of a high standard is currently being conducted worldwide such as that at [[Stellenbosch University]] in [[South Africa]].

Conventional [[breeding]] has helped establish triticale as a valuable crop and more particularly where conditions are less favourable for [[wheat]] cultivation. Notwithstanding the fact that triticale is a man-synthesized [[grain]], many initial limitations such as an inability to reproduce due to [[infertility]] and [[seed]] shrivelling, low yield and poor nutritional value have greatly been eliminated.

[[Tissue culture]] techniques with respect to [[wheat]] and triticale are continuously improving and the isolation and culturing of individual [[microspore]]s seems to hold the most promise. Many [[molecular]] markers can be applied to [[MAS|marker-assisted]] [[gene]] transfer, but the expression of R-[[genes]] in the new [[Genetics|genetic]] background of triticale remains to be investigated. (Baenziger ''et al.'' 2004) More than 750 [[wheat]] [[DNA|microsatellite]] primer pairs are available in public [[wheat]] [[breeding]] programs and could be exploited in the development of SSRs in triticale. (Baenziger ''et al.'' 2004) Another type of [[molecular]] marker known as a SNP (Single [[Nucleotide]] Polymorphism) is likely to have a significant impact on the future of triticale [[breed
ing]].

== Trivia ==
The popular TV series [[Star Trek]] and more specifically the episode [[The Trouble with Tribbles]] revolved around the protection of a grain developed from triticale, i.e. 'quadrotriticale'. A later episode (in the animated series) dealt with 'quintotriticale'. These two grains exist only in the realm of [[Star Trek]]. In addition, the video game [[Metroid Prime]] makes referral to 'deca-triticale'. (There is an inexplicit link within these names to the crops ploidy level, i.e. a specific characteristic of the [[genome]].)

==External links==
{{Memoryalpha|Quadrotriticale}}

==References==

*Andersen, S. B. (1989) Nuclear Genes Affecting Albinism in Wheat (''Triticum aestivum'' L.) Anther Culture. ''Theor. Appl. Genet''., '''78''', 879-883.
*Baenziger, P. S. ''et al.'' (2004) Transferability of SSR Markers Among Wheat, Rye, and Triticale. ''Theor. Appl. Genet''., '''108''', 1147-1150.
*Becker, D. ''et al.'' (1995) Fertile, Transgenic Triticale (x''Triticosecale'' Wittmack). ''Mol. Breed''., '''1''', 155-164.
*Becker, H.C. ''et al.'' (2001) Heterosis for Yield and Other Agronomic Traits of Winter Triticale F1 and F2 Hybrids. ''Plant Breeding'', '''120''', 351-353.
*Bennett, M. D. & Laurie, D. A. (1987) The Effect of Crossability Loci Kr1 and Kr2 on Fertilization Frequency in Haploid Wheat x Maize Crosses. ''Theor. Appl. Genet''., '''73''', 403-409.
*Bennet, M. D. ''et al.'' (1990) Wheat x Maize and Other Wide Sexual Hybrids: Their Potential for Genetic Manipulation and Crop Improvement. Gene Manipulation in Plant Improvement II: Proceedings of the 19th Stadler Genetics Symposium, 13-15. March 1989. Columbia, MO, USA, 95-126. Plenum Press, New York.
*Bernard, S. & Charmet, G. (1984) Diallel Analysis of Androgenetic Plant Production in Hexaploid Triticale (x ''Triticosecale'', Wittmack). ''Theor. appl. Genet''., '''69''', 55-61.
*Binka, A. ''et al.'' Efficient Method of Agrobacterium–mediated Transformation for Triticale (x ''Tritosecale'' Wittmack) ''Journal of Plant Growth Regulation''. Published online 28 July 2005. http://www.springerlink.com/content/g1214467t838p117/fulltext.html#CR6
*Burger, H. ''et al.'' (2003) Heterosis and Combining Ability for Grain Yield and Other Agronomic Traits in Winter Triticale. ''Plant Breeding'', '''122''', 318-321.
*Cavaleri, P. (2002) Selection Responses for Some Agronomic Traits in Hexaploid Triticale. ''Agriscientia'', '''XIX''', 45-50.
*Chaudhary, H. K. ''et al.'' (2005) Relative Efficiency of Different Gramineae Genera for Haploid Induction in Triticale and Triticale x Wheat Hybrids Through the Chromosome Elimination Technique. ''Plant Breeding'', '''124''', 147-153.
*Chelkowski, J. & Tyrka, M. (2004) Enhancing the Resistance of Triticale by Using Genes From Wheat and Rye. ''J. Appl. Genet''., '''45'''(3), 283-295.
*Gallais, A. (1984) Use of Indirect Selection in Plant Breeding. In: Hogenboon, N.G.(ed) ''et al.'' Efficiency In Plant Breeding, Proc. 10th Congress Eucarpia, Pudoc, Wageningen, 45-60.
*González, J.M., Jouve, N. (2000) Improvement of Anther Culture Media for Haploid Production in Triticale. ''Cereal Res. Commun''., '''28''', 65-72.
*Gonzalez, J.M. & Jouve, N. (2005) Microspore Development During ''in vitro'' Androgenesis in Triticale. Biologia Plantarum, 49 (1), 23-28.
*González, J.M. ''et al.'' (1997) Analysis of Anther Culture Response in Hexaploid Triticale. ''Plant Breeding'', '''116''', 302-304.
*Góral, H. (2002) Biological-breeding Aspects of Utilization of Heterosis in Triticale (x ''Triticosecale'', Wittmack) ''Zesz Nauk Akademii Rolniczejw Krakowie'', '''283''', 1-116.
*Góral, H. ''et al.'' (1999) Heterosis and Combining Ability in Spring Triticale (x ''Triticosecale'', Wittm.). ''Plant Breed. Seed Sci''., '''43''', 25-34.
*Góral, H. ''et al.'' (2005) Assessing Genetic Variation to Predict the Breeding Value of Winter Triticale Cultivars and Lines. ''J. Appl. Genet''., '''46'''(2), 125-131.
*Hede, A.R. (2000) A New Approach to Triticale Improvement. http://www.cimmyt.org
*Johansson, N. ''et al.'' (2000) Large-scale Production of Wheat and Triticale Double Haploids Through the Use of a Single-anther Culture Method. ''Plant Breeding'', '''119''', 455-459.
*Konzak, C. F. & Zhou, H. (1992) Genetic Control of Green Plant Regeneration From Anther Culture of Wheat. ''Genome'', '''35''', 957-961.
*Lukaszewski A. (1990) Frequency of 1RS.1AL and 1RS.1BL Translocations in United States Wheats. ''Crop Sci''., '''30''', 1151-1153.
*Marcinska, M. I. ''et al.'' (1998) Production of Doubled Haploids in Triticale (x ''Titicosecale'' Wittm.) by Means of Crosses with Maize (''Zea mays'' L.) Using Picloram and Dicamba. ''Plant Breeding'', '''117''', 211-215.
*Tikhnenko N. D. ''et al.'' (2002) The Effect of Parental Genotypes of Rye Lines on the Development of Quantitative Traits in Primary Octoploid Triticale: Plant Height. ''Russian Journal of Genetics'', '''39'''(1), 52–56.
*Triticale Production and Utilization Manual (2005) Copies available from bill.chapman@gov.ab.ca http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/fcd10535

{{Cereals}}
[[Category:Cereals]]
[[Category:Grasses]]
[[Category:Underutilized crops]]

Triticale - Revision history

Envoy at 09:55, 17 July 2007