Editing Triticale (section)

== Conventional breeding approaches ==
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The aim of a triticale breeding programme is mainly focused on the improvement of quantitative [[trait (biology)|trait]]s, such as grain yield, nutritional quality and plant height, as well as traits which are more difficult to improve, such as earlier maturity and improved test weight (a measure of bulk density). These traits are controlled by more than one [[gene]].<ref name="Manual">
{{cite web
|url=http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/fcd10535
|title=Triticale Production Manual
|publisher= Alberta Agriculture and Food and Development, Government of Alberta, Agricultural and Rural Development
|access-date=2009-06-23}}</ref> Problems arise, however, 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 International Maize and Wheat Improvement Center triticale breeding programme in 1964, the improvement in realised grain yield has been remarkable. In 1968, at [[Ciudad Obregón]], Sonora, 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.<ref name="Hede">{{cite web |url=http://repository.cimmyt.org/xmlui/bitstream/handle/10883/632/74311.pdf?sequence=1 |publisher=Corporate Communications, International Maize and Wheat Improvement Center |title=A New Approach to Triticale Improvement |work=Research Highlights of the CIMMYT Wheat Program 1999–2000 |location=Mexico, D. F. |year=2001 |author=A. R. Hede |pages=21–26 |access-date=18 July 2013 |archive-date=4 March 2016 |archive-url=https://web.archive.org/web/20160304071638/http://repository.cimmyt.org/xmlui/bitstream/handle/10883/632/74311.pdf?sequence=1 |url-status=dead }}</ref>

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 to evaluate [[heterosis]] in [[hexaploid]] triticale hybrids. To select the most promising parents for hybrid production, test crosses conducted in various environments are required, because the variance of their specific combining ability 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 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.{{Citation needed|date=June 2021}}

Triticale is useful as an animal feed [[grain]]. However, it is necessary to improve its milling and bread-making quality aspects to increase its potential for human consumption. The relationship between the constituent wheat and rye [[genomes]] were noted to produce meiotic irregularities, and genome instability and incompatibility presented numerous problems when attempts were made to improve triticale. This led to two alternative methods to study and improve its reproductive performance, namely, the improvement of the number of grains per floral spikelet 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)<ref name="Gallais">{{cite conference | first=A. | last=Gallais | title=Use of Indirect Selection in Plant Breeding |editor=Hogenboon, N. G. |display-editors=etal | book-title=Efficiency In Plant Breeding, Proc. 10th Congress Eucarpia | pages=45–60 | date=19–24 June 1983 | location=Pudoc, Wageningen, The Netherlands}}</ref>

Lodging (the toppling over of the plant stem, especially under windy conditions) resistance is a [[polygenic]]ally inherited (expression is controlled by many genes) trait, and has thus been an important breeding aim in the past.<ref name="Tikhnenko">{{cite journal | first=N. D. | last=Tikhnenko |author2=Tsvetkova, N. V. |author3=Voylokov, A. V. | title=The Effect of Parental Genotypes of Rye Lines on the Development of Quantitative Traits in Primary Octoploid Triticale: Plant Height | journal=[[Russian Journal of Genetics]] | volume=31 | issue=1 | pages=52–56 | date=23 August 2002 | doi=10.1023/A:1022070810919| s2cid=2659383 }}</ref> 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 {{ Convert | 20 | cm }} in plant height without causing any adverse effects.{{Citation needed|date=June 2021}}

A 2013 study found that hybrids have better yield stability under [[yield stress]] than do [[inbred line]]s.<ref name = "Stability" >{{ Cite journal
 | year = 2016
 | issue = 5
 | volume = 35
 | first5 = Narendra
 | first4 = Deepak
 | first3 = Premkumar
 | first2 = Uday
 | first1 = Abhishek
 | last5 = Singh
 | last4 = Bisht
 | last3 = Adhimoolam
 | last2 = Jha
 | last1 = Bohra
 | pages = 967–993
 | journal = Plant Cell Reports
 | issn = 0721-7714
 | eissn = 1432-203X
 | s2cid = 15935454
 | pmid = 26905724
 | doi = 10.1007/s00299-016-1949-3
 | title = Cytoplasmic male sterility (CMS) in hybrid breeding in field crops
 }}</ref><ref>{{ Cite journal
 | issue = 2
 | year = 2013
 | first5 = Jochen
 | first4 = Horst
 | first3 = Hans
 | first2 = Hans
 | first1 = Jonathan
 | last5 = Reif
 | last4 = Longin
 | last3 = Maurer
 | last2 = Piepho
 | last1 = Muhleisen
 | volume = 127
 | pages = 309–316
 | journal = Theoretical and Applied Genetics
 | issn = 0040-5752
 | eissn = 1432-2242
 | s2cid = 18542402
 | pmid = 24162154
 | doi = 10.1007/s00122-013-2219-1
 | title = Yield stability of hybrids versus lines in wheat, barley, and triticale
 }}</ref>