Figure 1.
Computer simulations to optimize MABS approach in wheat.
(A–C) Plabsim results for RPG recovery at different Q-values including the minimum and maximum value using 110 (A), 208 (B) and 320 (C) markers for two-stage (red line), three-stage (green line) and four-stage (blue line) selection. (D–E) Represents %RPG recovered with increasing BC generation at constant population size of 100 per BC (D), and with constant increase in population size (E), using 110 (red line), 208 (blue lines) and 320 (pink lines) markers and four-stage selection strategy. Solid lines corresponds to Qmax values, whereas dotted lines represents Qmin values. (F–H) Corresponds to the number of MDP required in each generation using two- (red line), three- (green line) and four-stage (blue line) selection strategy for 208 (F), 110 (G) and 320 (H) markers. (I–K) Represents the Qmax (shaded bars) and Qmin values (solid bars) of RPG recovery in BC1 (green bars) and BC2 (red bars) generation using variable population size per BC and four-stage selection, and for 110 (I), 208 (J) and 320 (K) markers. Blue dots correspond to the number of MDPs required.
Figure 2.
Schematic representation of introgression of stripe rust resistance gene Yr15 into the cultivar ‘Zak’ using MABS.
Table 1.
Polymorphism survey of ‘Zak’ and the Yr15 gene donor line using SSR markers.
Table 2.
Recurrent parent genome (RPG) recovery by MABS.
Figure 3.
Comparison of cultivar ‘Zak’ derivatives carrying stripe rust resistance gene Yr15 developed with (WA8059) and without (WA8046) MABS.
(A) Graphical genotypes, showing parental derivation with green bars representing the homozygous RP alleles, red bars indicate the marker allele homozygous for DP, and heterozygous loci were marked with half green and half red bars. Orange star represents the carrier chromosome, with red arrow corresponding to the approximate position of the target gene (Yr15) on the carrier chromosome and blue dots denotes relative position of the SSR markers used for the comparison. (B) Comparison of various parameters recorded during field evaluation and quality analysis of these three lines done at different locations.
Table 3.
Number of plants required to recover single and/or double recombinant (Rec.) with desired physical size.
Table 4.
Physical Locations of Genes/Markers, recombination (Rec.) in GRRs in Wheat Genome.
Figure 4.
Proposed MABS strategy in wheat for introgressing a target gene while recovering 97% or more RPG in just two BCs.
Figure 5.
Strategy for selection of markers for marker-assisted backcross breeding program.
Example is given for consensus chromosome of group 1. Names of the GRRs are provided on the right side of a consensus chromosome. In the nomenclature of GRRs (e.g. ‘1S0.8’), the first digit represents wheat homoeologous group followed by the arm location either as short arm (S) or long arm (L). The last two numeral numbers represent GRR location as fraction length (FL) of the chromosome (e.g. 0.8 for ‘1S0.8’). Along with GRRs the recombination in cM observed for particular GRRs is also given. On the left side of the consensus chromosome, * denotes the number of markers selected for a particular GRR region. Number of markers selected for each GRR was variable. For example the regions showing high recombination, like GRR 1L0.9, three markers were selected, two flanking and one from the middle of the GRR, whereas in the case of a GRR like 1S0.4, only two markers flanking the GRR was selected.