Preliminary Exploration of the Source, Spread, and Distribution of Rht24 Reducing Height in Bread Wheat

Abstract

Rht24 is a major dwarfing allele that not only reduces plant height but also increases grain weight. The objective of this study was to trace the source, spread, and distribution of Rht24 and determine its frequency in conjunction with other important dwarfing alleles for Rht1 (Rht‐B1b), Rht2 (Rht‐D1b), and Rht8. Allele‐specific cleaved amplified polymorphic sequence (CAPS) markers were developed for accurate and effective genotyping of Rht1 and Rht2, and closely linked flanking markers were used for genotyping of Rht8 and Rht24. Marker analysis showed that Rht24 occurs at a higher frequency (84.2%) than other important dwarfing alleles in elite wheat (Triticum aestivum L.) varieties and usually couples with Rht2 or Rht8. Genotyping of old varieties and landraces showed that Rht24 was widely used in wheat breeding before the Green Revolution (GR). ‘Akakomugi’ and ‘Norin 10’, the donors of Rht8 and GR genes Rht1 and Rht2, respectively, harbored Rht24, so Rht24 likely followed the transfer routes of GR genes and Rht8 to spread worldwide. Pedigree analysis showed that many Chinese elite lines and backbone parents were derived from Akakomugi, contributing to the high frequency of Rht24 in Chinese varieties. Additionally, Norin 10‐derived semidwarf varieties from the CIMMYT were widely used in Chinese wheat breeding. Finally, Rht24 was also detected in 30 old Chinese varieties and landraces. Overall, these findings show that the presence of Rht24 in modern Chinese elite varieties originated from Akakomugi, Norin 10, or Chinese landraces. Thus, Rht24 was introgressed early, spread widely, and became genetically fixed in a wide range of modern Chinese wheat germplasm.

Green revolution ‘stumbles’ in a dry environment: Dwarf wheat with Rht genes fails to produce higher grain yield than taller plants under drought

“…The dwarfing genes Rht24 and Rht25 generate a reduction in plant height of about 8-12%, which is less than half that of the Rht-B1b and Rht-D1b alleles (20 and 25%, respectively). Potentially, this also provides a useful alternative dwarfing genotype for drought-affected environments, with better growth, biomass and yield in dry conditions Tian et al, 2017Tian et al, , 2019Würschum et al, 2017).…”

Agronomic and Physiological Traits, and Associated Quantitative Trait Loci (QTL) Affecting Yield Response in Wheat (Triticum aestivum L.): A Review

“…Additive gene action was reported between Rht12 and Ppd-D1 such that incorporation of Ppd-D1a enhanced flowering, and improved yield and yield-related traits of Rht12 dwarf plants, suggesting that the combination of Rht12 and Ppd-D1a may increase use of Rht12 in wheat breeding (Chen et al, 2018b). Tian et al (2019) showed that a combination of diverse height reducing genes have already been incorporated in elite Chinese wheat genotypes. For instance, combinations of Rht24+Rht1, Rht24+Rht2, Rht24+Rht8, Rht1+Rht8, Rht2+Rht8, Rht24+Rht1+Rht8, Rht24+Rht2+Rht8 occurred at frequencies of 86, 117, 137, 56, 77, 47, and 70%, respectively in Chinese wheat genotypes.…”

“…Rht4 , Rht5 , Rht8 , Rht11 , Rht12 , Rht13 , Rht24 , and Rht25 ) have negligible effects on biomass production, whereas some (i.e. Rht4 , Rht12 ; Rht13 ; Rht24 ) can increase above-ground biomass, kernel weight, and grain yield (Rebetzke et al, 2012a; Rebetzke et al, 2012b; Yang et al, 2015; Würschum et al, 2017; Tian et al, 2019). The Rht24b allele is already used in combination with the two Rht‐1b semi‐dwarfing genes in wheat breeding (Würschum et al, 2017; Tian et al, 2019).…”

“…Rht4 , Rht12 ; Rht13 ; Rht24 ) can increase above-ground biomass, kernel weight, and grain yield (Rebetzke et al, 2012a; Rebetzke et al, 2012b; Yang et al, 2015; Würschum et al, 2017; Tian et al, 2019). The Rht24b allele is already used in combination with the two Rht‐1b semi‐dwarfing genes in wheat breeding (Würschum et al, 2017; Tian et al, 2019). As a result, Rht24 utilization has increased in European countries, China and the USA, indicating that wheat breeders have actively selected for this locus for cultivar development to improve lodging resistance and grain yield potential (Würschum et al, 2017; Tian et al, 2019).…”

“…The Rht24b allele is already used in combination with the two Rht‐1b semi‐dwarfing genes in wheat breeding (Würschum et al, 2017; Tian et al, 2019). As a result, Rht24 utilization has increased in European countries, China and the USA, indicating that wheat breeders have actively selected for this locus for cultivar development to improve lodging resistance and grain yield potential (Würschum et al, 2017; Tian et al, 2019). Rht24 occurs at a frequency of about 84.2% than other important dwarfing alleles in elite wheat varieties in China and usually couples with Rht2 or Rht8 (Tian et al, 2019).…”