Identification and characterization of Rht25, a locus on chromosome arm 6AS affecting wheat plant height, heading time, and spike development

Abstract

This study identified Rht25, a new plant height locus on wheat chromosome arm 6AS, and characterized its pleiotropic effects on important agronomic traits. Understanding genes regulating wheat plant height is important to optimize harvest index and maximize grain yield. In modern wheat varieties grown under high-input conditions, the gibberellin-insensitive semi-dwarfing alleles Rht-B1b and Rht-D1b have been used extensively to confer lodging tolerance and improve harvest index. However, negative pleiotropic effects of these alleles (e.g., poor seedling emergence and reduced biomass) can cause yield losses in hot and dry environments. As part of current efforts to diversify the dwarfing alleles used in wheat breeding, we identified a quantitative trait locus (QHt.ucw-6AS) affecting plant height in the proximal region of chromosome arm 6AS (< 0.4 cM from the centromere). Using a large segregating population (~ 2800 gametes) and extensive progeny tests (70-93 plants per recombinant family), we mapped QHt.ucw-6AS as a Mendelian locus to a 0.2 cM interval (144.0-148.3 Mb, IWGSC Ref Seq v1.0) and show that it is different from Rht18. QHt.ucw-6AS is officially designated as Rht25, with Rht25a representing the height-increasing allele and Rht25b the dwarfing allele. The average dwarfing effect of Rht25b was found to be approximately half of the effect observed for Rht-B1b and Rht-D1b, and the effect is greater in the presence of the height-increasing Rht-B1a and Rht-D1a alleles than in the presence of the dwarfing alleles. Rht25b is gibberellin-sensitive and shows significant pleiotropic effects on coleoptile length, heading date, spike length, spikelet number, spikelet density, and grain weight. Rht25 represents a new alternative dwarfing locus that should be evaluated for its potential to improve wheat yield in different environments.

Mining the stable quantitative trait loci for agronomic traits in wheat (Triticum aestivum L.) based on an introgression line population

“…To date, the dwarf genes identified on chromosome 6A include: Rht14, Rht16, Rht18, Rht24, and Rht25. The Rht24 locus is located between the Xbarc103 and Xwmc256 markers [16] and the remaining four genes are close to the Xbarc3 marker [17][18][19][20]. Haque et al [17] thought Rht14 was allelic to Rht16 and Rht18 and linked to SSR marker Xbarc3 on chromosome 6AS.…”

A wheat dominant dwarfing line with Rht12, which reduces stem cell length and affects gibberellic acid synthesis, is a 5AL terminal deletion line

“…Recently, GA‐responsive dwarfing gene Rht18 was found to reduce GA 1 content by upregulating TaGA2oxA9 which encodes GA metabolic enzyme GA 2‐oxidase (GA2ox) that metabolizes GA biosynthetic intermediate GA 12 into inactive product GA 110 (Ford et al ., ). Rht24 and Rht25 , two newly discovered GA‐responsive genes, were reported in common wheat; however, the mechanisms remain unclear and the genes have yet to be cloned (Mo et al ., ; Würschum et al . ).…”

EFFECTS OF DWARFING WHEAT (Triticum aestivum L.) AND RYE (Secale cereale L.) GENES IN SPRING TRITICALE SEGREGATING POPULATION AS STUDIED IN POT TRIALS

“…Наибольшее распространение в коммерческих сортах пшеницы получили гены Rht-B1b (=Rht1), Rht-D1b (=Rht2), Rht-8c, Rht-B1e (=Rht11). Они действуют даже при высоких дозах удобрений и обладают плейотропным эффектом в отношении множества хозяйственно ценных признаков (11)(12)(13). У растений пшеницы в присутствии нечувствительных к гиббереллину генов короткостебельности Rht-B1b, Rht-D1b, Rht-B1e высота снижается в среднем на 10-15 % по сравнению с таковой у носителей аллеля дикого типа Rht-B1a (14)(15)(16).…”