Marker-assisted introgression of genes into rye translocation leads to the improvement in bread making quality of wheat (Triticum aestivum L.)

Abstract

Introgression of genes from related species can be a powerful way to genetically improve crop yields, but selection for one trait can come at the cost to others. Wheat varieties with translocation of the short arm of chromosome 1 from the B genome of wheat (1BS) with the short arm of chromosome 1 from rye (1RS) are popular globally for their positive effect on yield and stress resistance. Unfortunately, this translocation (1BL.1RS) is also associated with poor bread making quality, mainly due to the presence of Sec-1 on its proximal end, encoding secalin proteins, and the absence of Glu-B3/Gli-B1-linked loci on its distal end, encoding low molecular weight glutenin subunits (LMW-GS). The present study aims to replace these two important loci on the 1RS arm with the wheat 1BS loci, in two popular Indian wheat varieties, PBW550 and DBW17, to improve their bread-making quality. Two donor lines in the cultivar Pavon background with absence of the Sec-1 locus and presence of the Glu-B3/Gli-B1 locus, respectively, were crossed and backcrossed with these two selected wheat varieties. In the advancing generations, marker assisted foreground selection was done for Sec-1^- and Glu-B3/Gli-B1⁺ loci while recurrent parent recovery was done with the help of SSR markers. BC₂F₅ and BC₂F₆ near isosgenic lines (NILs) with absence of Sec-1 and presence of Glu-B3/Gli-B1 loci were evaluated for two years in replicated yield trials. As a result of this selection, thirty promising lines were generated that demonstrated improved bread making quality but also balanced with improved yield-related traits compared to the parental strains. The study demonstrates the benefits of using marker-assisted selection to replace a few loci with negative effects within larger alien translocations for crop improvement.

Fig. 1. Gene transfer through marker assisted selection.

Schematic representation of the breeding scheme for marker assisted transfer of two loci Sec-1⁻ and GluB3/Gli-B1 in two wheat lines PBW550 and DBW17 carrying the stripe rust resistance gene Yr5.

Fig. 2. Pairwise correlation analysis.

Correlation coefficient of different yield-related traits in near isogenic lines (NILs) across two generations, BC₂F₅ and BC₂F₆. PH-Plant height, SL-Spike length, SN- Spikelet number/spike, TNpM-Tillers number per meter, TGW-Thousand grain weight, YD-Total Yield, HI-Harvest Index.

Fig. 3. Multivariate analysis.

a Principal component analysis, and (b) Multivariate analysis by structural equation modeling among different yield-related traits in near isogenic lines (NILs) across two generations, BC₂F₅ andBC₂F₆. †Red and blue colour represents eigen vectors in season 2018–19, and 2019–20, respectively, for (a) ††Red, and blue colour represents negative, and positive contributions, respectively, for (b) †††PH-Plant height, SL-Spike length, SN- Spikelet number/spike, TNpM-Tillers number per meter, TGW-Thousand grain weight, YD-Total Yield, HI-Harvest Index.

Fig. 4. Presence or absence of the Glu-B3 locus encoded 42–50 kDa proteins in the parental lines and BC₂F₆ near isogenic lines (NILs), resolved on 10% polyacrylamide gel.

P1-Pavon40:9, P2-Pavon44:38, P3-PBW550+Yr5, P4-DBW17+Yr5 and 1 to 8- NILs derived from cross Pavon40:9XPBW550/DBW17; Arrows represent the presence of the Glu-B3 locus encoded 42–50kDa proteins.

Fig. 5. Presence or absence of the Sec-1 locus encoded 42–55 KDa proteins in the parental lines and BC₂F₆ near isogenic lines (NILs) resolved on 15% polyacrylamide gel. C- negative control (Chinese spring), P1-Pavon44:38, P2-PBW550+Yr5, and 1 to 10 - NILs derived from cross Pavon44:38XPBW550/DW17.

White arrow represents the presence of the Sec-1 locus encoded protein in P2 and black arrow represents absence of the Sec-1 locus encoded proteins in NILs.