Inheritance and genetic mapping of the reduced height (Rht18) gene in wheat

Authors: GRANT, NATHAN - Washington State University; MOHAN, AMITA - Washington State University; Sandhu, Devinder; GILL, KULVINDER - Washington State University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/11/2018
Publication Date: 7/15/2018
Publication URL: http://handle.nal.usda.gov/10113/6481475
Citation: Grant, N., Mohan, A., Sandhu, D., Gill, K.S. 2018. Inheritance and genetic mapping of the reduced height (Rht18) gene in wheat. Plants. 7(3):58. https://doi.org/10.3390/plants7030058.
DOI: https://doi.org/10.3390/plants7030058

Interpretive Summary: The introduction of semi-dwarf varieties that are more responsive to changing agriculture practices was pivotal in bringing green revolution by increasing crop production particularly in developing countries. The development of semi-dwarf cultivars in wheat can be attributed to a shorter yet stronger stem that accommodates high yields and prevents lodging. Of the 21 reduced height genes reported in wheat, only a few have been characterized in detail and only three have been utilized in breeding programs. Association of some negative effects with the common reduced height genes and the limited genetic variability in dwarf lines, are becoming bottlenecks for future wheat improvement. The objectives of this investigation were to characterize a reduced height gene (Rht18), genetically map it to a wheat chromosome and identify suitable semi-dwarf lines with a potential to be used in a wheat breeding program. Inheritance studies indicate that the dwarf phenotype due to Rht18 is semi-dominant over tall and in addition to Rht18, there may be some modifier genes playing role in regulation plant height. We have mapped Rht18 to chromosome 6A and identified DNA markers associated with the gene. Due to the complexity of the height trait and effect of environmental conditions on the trait, identification of markers closer to the Rht18 gene may assist wheat breeders in early identification of dwarfing lines for breeding populations. Further, conducting the genomic and agronomic characterization of this mutant gene may become instrumental in developing a better dwarfing system in wheat. Additionally, we have identified a semi-dwarf line with superior agronomic characters that might have potential to be used in wheat breeding.

Technical Abstract: Short statured plants revolutionized agriculture during 1960’s due to their ability to resist lodging, increased response to fertilizers and improved partitioning of assimilates which led to yield gains. Of more than 21 reduced height (Rht) genes reported in wheat, only three, Rht-B1b and Rht-D1b and Rht8 were extensively used in wheat breeding programs. The remaining reduced height mutants have not been utilized in breeding programs due to the lack of characterization. In the present study, we determined inheritance of Rht18 and developed a genetic linkage map of the region containing Rht18. The height distribution of the F2 population was skewed towards the mutant parent, indicating that the dwarf allele (Rht18) is semi-dominant over the tall allele (rht18). Rht18 was mapped on chromosome 6A between marker barc146 and cfd190 with a genetic distance of 26.2 and 17.3 cM, respectively. In addition to plant height, agronomically important traits like awns and tiller numbers were also studied in the bi-parental population. Although, average tiller number was very similar in both parents, the F2 population displayed a normal distribution for tiller number with the majority of plants having phenotype similar to the parents. Transgressive segregation was observed for plant height and tiller number in F2 population. This study enabled us to select a semi-dwarf line with superior agronomic characteristics that could be utilized in a breeding program. The identification of SSRs associated with Rht18 may improve breeders’ effectiveness in selecting desired semi-dwarf lines for developing new wheat cultivars.