Identification, distribution and effects on agronomic traits of the semi-dwarfing Rht alleles in Bulgarian common wheat cultivars

Abstract

Bulgarian common wheat cultivars released in the period 1925-2003 were studied using the gibberellic acid (GA) test and microsatellite analysis of the Xgwm261 locus on chromosome 2DS to identify the semi-dwarfing (Rht) genes. The old cultivars, isolated through selection from landraces, carried rare alleles (211-and 215-bp) at Xgwm261 locus, and those developed by hybridisation to foreign cultivars, carried the 165-and 174-bp alleles. Forty-two (55.3%) of 76 modern cultivars were GA-responsive. The 192-bp allele, diagnostic for Rht8, was observed in 64 (84.2%) modern cultivars, of which 37 carry Rht8 alone, and 27 possess a combination of Rht8 and a GA-insensitive allele viz. Rht-B1d (17); Rht-D1b (6) and Rht-B1b (4). The 174-bp allele is present in seven cultivars, only one of which is photoperiod-sensitive, and the rest are day-length insensitive. The 203-bp allele was found in six modern cultivars. Cultivars carrying the Rht8 allele are the most widespread and some of them have been cultivated for a long period. Cultivars with the 'Saitama 27' allele (Rht-B1d) are the most productive and are second in distribution in the country. The recently observed trend for increasing the proportion of cultivars with GA-insensitive Rht genes is probably due to their combination with the 192-bp allele of Xgwm261 locus tightly linked to the Ppd-D1, to the break of the link between the 174-bp allele and ppd-D1, and to the introduction of other genes influencing flowering time.

Coleoptile length and plant height of modern tall and semi-dwarf European winter wheat varieties

“…Winter wheat varieties from Central European countries exerted the main negative effect on this correlation. Pobeda, the only variety out of 14 Central European varieties was investigated for Rht genes and possessed Rht8 [21]. No evidence on the rest of the varieties was found.…”

“…However, involvement of exotic germplasm with a complex of undesirable agronomic traits can impede breeding. Many Southern and Central European varieties possess Rht8 alone or in combinations with Rht-D1 or Rht-B1 [5,21]. Probably, some of them possess long coleoptiles.…”

Impact of Growth Habit and Architecture Genes on Adaptation and Performance of Bread Wheat

“…Wheat genotypes with only one copy allele are photoperiod-sensitive whereas an increased copy number (2-4 copies) results in a day-neutral, early flowering phenotype. A complementary study [100] confirmed that wheat genotypes with the three-copy allele (termed Ppd-B1a) and the four-copy allele (termed Ppd-B1c) exhibit reduced days to heading as compared to the onecopy allele (termed Ppd-B1b) whereas the two-copy allele (termed Ppd-B1d) displays increased days to heading (late flowering). These results indicate that the CNV at the Ppd-B1 locus contributes in fine-tuning the adaptation of wheat to local climatic conditions, in addition to the major effect of Ppd-D1.…”

“…Therefore, breeding for wheat cultivars with flexible response in different environments and that exhibit superior performance under extreme conditions, such as hot and dry environments, should become a priority. Photoperiod insensitivity is usually an advantage in most regions [100]. Therefore, selecting for the trait and incorporating genes for other complementary traits, such as preharvest sprouting resistance into the advanced lines, could be an added advantage in addition to significant yield improvement.…”

“…This allows the transfer of genotypes between regions with different climatic conditions but still maintains their level of agronomic performance [5]. The Ppd-D1a allele has been selected for by plant breeders in different countries for several decades to enhance yield in certain climatic conditions [10,46,100]. Selecting for favorable alleles also allows the development of allele-specific DNA markers for efficient detection of extensive allelic variation among genes controlling traits of agronomic importance [35,46,95].…”