Swedish Spring Wheat Varieties with the Rare High Grain Protein Allele of NAM-B1 Differ in Leaf Senescence and Grain Mineral Content

Abstract

Some Swedish spring wheat varieties have recently been shown to carry a rare wildtype (wt) allele of the gene NAM-B1, known to affect leaf senescence and nutrient retranslocation to the grain. The wt allele is believed to increase grain protein concentration and has attracted interest from breeders since it could contribute to higher grain quality and more nitrogen-efficient varieties. This study investigated whether Swedish varieties with the wt allele differ from varieties with one of the more common, non-functional alleles in order to examine the effect of the gene in a wide genetic background, and possibly explain why the allele has been retained in Swedish varieties. Forty varieties of spring wheat differing in NAM-B1 allele type were cultivated under controlled conditions. Senescence was monitored and grains were harvested and analyzed for mineral nutrient concentration. Varieties with the wt allele reached anthesis earlier and completed senescence faster than varieties with the non-functional allele. The wt varieties also had more ears, lighter grains and higher yields of P and K. Contrary to previous information on effects of the wt allele, our wt varieties did not have increased grain N concentration or grain N yield. In addition, temporal studies showed that straw length has decreased but grain N yield has remained unaffected over a century of Swedish spring wheat breeding. The faster development of wt varieties supports the hypothesis of NAM-B1 being preserved in Fennoscandia, with its short growing season, because of accelerated development conferred by the NAM-B1 wt allele. Although the possible effects of other gene actions were impossible to distinguish, the genetic resource of Fennoscandian spring wheats with the wt NAM-B1 allele is interesting to investigate further for breeding purposes.

Contrasting growth pattern and nitrogen economy in ancient and modern wheat varieties

“…The higher C N,g in ancient than modern genotypes in our study is in line with literature reporting higher protein content in ancient than in modern genotypes (Abdelaal et al 1995;Marconi et al 1999), and could be related to the action of a functional allele of the gene NAM-B1 often more present in ancient genotypes than modern breeds (Uauy et al 2006;Hagenblad et al 2012). The gene NAM-B1 is of interest for breeding purposes, but its effect across different genetic backgrounds and physical environments is still unclear (Asplund et al 2013). The association of high C N,g with low grain yield observed in ancient wheats grown in the lower fertilization treatment points to a low grain starch content, although this hypothesis cannot be verified as starch content was not assessed.…”

“…Of the three NUE components, the higher N uptake efficiency U N (and mean relative N accumulation rate, R N ) and grain N concentration (C N,g ) in the ancient genotypes could be of interest in the context of breeding for nutrient use efficiency. More specifically, breeding for increased C N,g is facilitated by the available knowledge on the link between grain nutrient concentration and the gene NAM-B1, but the relationship needs to be further investigated, especially with regard to the effects of NAM-B1 in the relevant genetic backgrounds and environments (Asplund et al 2013). It is also possible that the greater total leaf area in combination with more tillers of the ancient hulled wheat genotypes, also reported by Wacker et al (2002), is of some interest in terms of reduced requirement of weed control, although the greater leaf area we observed was caused by taller stature and thus enhanced risk of lodging (Ma et al 2012).…”

Detection of NAM-A1 Natural Variants in Bread Wheat Reveals Differences in Haplotype Distribution between a Worldwide Core Collection and European Elite Germplasm

“…Nevertheless, hexaploid wheats have five other NAM genes, three paralogous (on chromosomes 2A, 2B and 2D) and two homoeologous (on chromosomes 6A and 6D) of which NAM-A1 (6A) has the same role as NAM-B1 [4,8]. Most studies on NAM wheat genes used mutants [4,8], near isogenic lines [9][10][11][12] or RNAi lines [3,4] and few studies have focused on the cultivated diversity [6,13]. This paper aims to characterize natural variants of NAM-A1 in hexaploid bread wheat and to hypothesize on the biological mechanisms explaining their effects.…”

New genetic resources in wheat breeding for an increased grain protein content

“…В их число входят сорта Stanley к-22165 из Канады; Diamant к-25019 и Rubin к-38203 из Швеции; Ruskea к-25845, Sopu к-33949 и Luja к-57198 из Финляндии; Nora к-43714 и Lanor к-53573 из Норвегии и др. (Asplund et al, 2013).…”