Editing Triticale (section)

== Biology and genetics ==
{{More citations needed section|date=June 2021}}
Earlier work with wheat-rye crosses was difficult due to low survival of the resulting hybrid [[embryo]] and spontaneous chromosome doubling. These two factors were difficult to predict and control. To improve the viability of the embryo and thus avoid its abortion, ''[[in vitro]]'' culture techniques were developed (Laibach, 1925).{{full citation needed|date=March 2017}} [[Colchicine]] was used as a chemical agent to double the chromosomes.<ref>{{cite journal|last1=Blakeslee|first1=Albert F.|last2=Avery|first2=Amos G.|title=Methods of Inducing Doubling of Chromosomes in Plants|journal=Journal of Heredity|date=December 1937|volume=28|issue=12|pages=393–411|doi=10.1093/oxfordjournals.jhered.a104294}}</ref> After these developments, a new era of triticale [[Artificial selection|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).{{full citation needed|date=March 2017}} 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.{{cn|date=September 2023}}

Triticale is essentially a self-fertilizing, or 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.{{cn|date=September 2023}}

''{{ Visible anchor | Sr27 }}'' is a [[stem rust]] resistance gene which is commonly found in triticale.<ref name="Sr27-GlobalRust">{{cite web | title=''Sr27'' | website=Borlaug Global Rust Initiative | url=http://globalrust.org/gene/sr27 | access-date=2021-07-24}}</ref> Originally from [[rye]]<ref name="Singh-et-al-2011">{{cite journal | last1=Singh | first1=Ravi P. | last2=Hodson | first2=David P. | last3=Huerta-Espino | first3=Julio | last4=Jin | first4=Yue | last5=Bhavani | first5=Sridhar | last6=Njau | first6=Peter | last7=Herrera-Foessel | first7=Sybil | last8=Singh | first8=Pawan K. | last9=Singh | first9=Sukhwinder | last10=Govindan | first10=Velu|display-authors=3 | title=The Emergence of Ug99 Races of the Stem Rust Fungus is a Threat to World Wheat Production | journal=Annual Review of Phytopathology| volume=49 | issue=1 | date=2011-09-08 | issn=0066-4286 | doi=10.1146/annurev-phyto-072910-095423 | pages=465–481| pmid=21568701 }}</ref> (Imperial rye),<ref name="Park-Wellings-2012">{{cite journal | last1=Park | first1=Robert F. | last2=Wellings | first2=Colin R. | title=Somatic Hybridization in the Uredinales | journal=Annual Review of Phytopathology | volume=50 | issue=1 | date=2012-09-08 | issn=0066-4286 | doi=10.1146/annurev-phyto-072910-095405 | pages=219–239| pmid=22920559 }}</ref> now ({{as of|2021|lc=yes}}) widely found in triticale.<ref name="Upadhyaya-et-al-2021">{{cite journal|last1=Upadhyaya|first1=Narayana M.|last2=Mago|first2=Rohit|last3=Panwar|first3=Vinay|last4=Hewitt|first4=Tim|last5=Luo|first5=Ming|last6=Chen|first6=Jian|last7=Sperschneider|first7=Jana|last8=Nguyen-Phuc|first8=Hoa|last9=Wang|first9=Aihua|last10=Ortiz|first10=Diana|last11=Hac|first11=Luch|last12=Bhatt|first12=Dhara|last13=Li|first13=Feng|last14=Zhang|first14=Jianping|last15=Ayliffe|first15=Michael|last16=Figueroa|first16=Melania|last17=Kanyuka|first17=Kostya|last18=Ellis|first18=Jeffrey G.|last19=Dodds|first19=Peter N.|display-authors=3 |title=Genomics accelerated isolation of a new stem rust avirulence gene–wheat resistance gene pair|journal=Nature Plants|year=2021|volume=7|issue=9|pages=1220–1228|issn=2055-0278|doi=10.1038/s41477-021-00971-5|pmid=34294906|s2cid=236199741|url=https://repository.rothamsted.ac.uk/download/911a82b1b12af18ce55d120f48f3568494a06549fc42318ed814d03d057c0e37/4800766/10378_1_supp_129049_q96vf9_convrt.pdf}}</ref> Located on the 3A chromosome arm,<ref name="Sr27-GlobalRust" /> originally from 3R.<ref name="McIntosh-et-al-1995">{{cite book | last1=McIntosh | first1=RA | last2=Wellings | first2=CR | last3=Park | first3=RF | title=Wheat Rusts - An Atlas of Resistance Genes | publisher=[[Springer Publishing|Springer]] | isbn=9789401040419 | date=1995}}</ref> Virulence has been observed in field by [[Stem rust|''Puccinia graminis'' f. sp. ''secalis'']] (''Pgs'') and in an artificial cross ''Pgs'' {{times}} [[Stem rust|''Puccinia graminis'' f. sp. ''tritici'']] (''Pgt'').<ref name="Park-Wellings-2012" /> When successful, ''Sr27'' is among the few ''Sr''s that does not even allow the underdeveloped [[uredinia]] and slight degree of sporulation commonly allowed by most ''Sr''s.<ref name="Singh-et-al-2011" /> Instead there are [[necrotic]] or [[chlorotic]] flecks.<ref name="Roelfs-1988">{{cite journal | last=Roelfs | first=A P | title=Genetic Control of Phenotypes in Wheat Stem Rust | journal=[[Annual Review of Phytopathology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=26 | issue=1 | year=1988 | issn=0066-4286 | doi=10.1146/annurev.py.26.090188.002031 | pages=351–367}}</ref> Deployment in triticale in [[New South Wales]] and [[Queensland]], Australia, however, rapidly showed virulence between 1982 and 1984 – the first virulence on this gene in the world.<ref name="McIntosh-Brown-1997">{{cite journal | last1=McIntosh | first1=R. A. | last2=Brown | first2=G. N. | title=Anticipatory Breeding for Resistance to Rust Diseases in Wheat | journal=[[Annual Review of Phytopathology]] | publisher=[[Annual Reviews (publisher)|Annual Reviews]] | volume=35 | issue=1 | year=1997 | issn=0066-4286 | doi=10.1146/annurev.phyto.35.1.311 | pages=311–326| pmid=15012526 }}</ref><ref name="Singh-et-al-2011" /><ref name="McIntosh-et-al-1995" /> (This was especially associated with the cultivar Coorong.)<ref name="McIntosh-Brown-1997" /><ref name="Johnson-1984">{{cite journal | last=Johnson | first=R | title=A Critical Analysis of Durable Resistance | journal=Annual Review of Phytopathology| volume=22 | issue=1 | year=1984 | issn=0066-4286 | doi=10.1146/annurev.py.22.090184.001521 | pages=309–330}}</ref> Therefore, the International Maize and Wheat Improvement Center's triticale offerings were tested and many were found to depend solely on ''Sr27''.<ref name="Johnson-1984" /><ref name="McIntosh-et-al-1995" /> Four years later, in 1988 virulence was found in [[South Africa]]. ''Sr27'' has become less common in CIMMYT triticales since the mid-'80s.<ref name="McIntosh-et-al-1995" />