Pseudo-backcrossing design for rapidly pyramiding multiple traits into a preferential rice variety

Abstract

BackgroundPyramiding multiple genes into a desirable genetic background can take years to accomplish. In this paper, a pseudo-backcrossing scheme was designed to shorten the backcrossing cycle needed. PinK3, an aromatic and potentially high-yielding rice variety—although one that is intolerant to flash flooding (Sub) and susceptible to bacterial leaf blight (BB), leaf-neck blast (BL) and the brown planthopper (BPH)—was used as a genetic basis for significant improvements through gene pyramiding.ResultsFour resistance donors with five target genes (Sub1A-C, xa5, Xa21, TPS and SSIIa) and three QTLs (qBph3, qBL1 and qBL11) were backcrossed individually using markers into the pseudo-recurrent parent ‘PinK3’ via one cycle of backcrossing followed by two cycles of pseudo-backcrossing and three selfings with rigorous foreground marker-assisted selection. In total, 29 pseudo-backcross inbred lines (BILs) were developed. Genome composition was surveyed using 61 simple sequence repeats (SSRs), 35 of which were located on six carrier chromosomes, with the remainder located on six non-carrier chromosomes. The recurrent genome content (%RGC) and donor genome content (%DGC), which were based on the physical positions of BC1F2, ranged from 69.99 to 88.98% and 11.02 to 30.01%, respectively. For the pseudo-BC3F3BILs, the %RGC and %DGC ranged from 74.50 to 81.30% and 18.70 to 25.50%, respectively. These results indicated that without direct background selection, no further increases in %RGC were obtained during pseudo-backcrossing, whereas rigorous foreground marker-assisted selection tended to reduce linkage drag during pseudo-backcrossing. The evaluation of new traits in selected pseudo-BC3F3BILs indicated significant improvements in resistance to BB, BL, BPH and Sub compared with PinK3, as well as significant improvements in grain yield (21-68%) over the donors, although yield was 7-26% lower than in ‘PinK3’. All pyramided lines were aromatic and exhibited improved starch profiles, rendering them suitable for industrial food applications.ConclusionsResults show that our new pyramiding platform, which is based on marker-assisted pseudo-backcrossing, can fix five target genes and three QTLs into a high-yielding pseudo-recurrent background within seven breeding cycles in four years. This multiple pseudo-backcrossing platform decreases the time required to generate new rice varieties exhibiting complex, durable resistance to biotic and abiotic stresses in backgrounds with desirable qualities.Electronic supplementary materialThe online version of this article (doi:10.1186/s12284-014-0035-0) contains supplementary material, which is available to authorized users.

Genome Wide Single Locus Single Trait, Multi-Locus and Multi-Trait Association Mapping for Some Important Agronomic Traits in Common Wheat (T. aestivum L.)

“…This should allow selection of genotypes with superior alleles for main effect as well as epistatic QTL. Alternatively, desirable alleles available in the above eight genotypes may be introgressed and rapidly pyramided into the currently grown wheat cultivars to develop superior wheat genotype following pseudo-backcrossing as done in rice recently [ 65 ]. These improved genotype(s) may result into cultivars with improved agronomic performance and grain quality or may constitute important genetic resource for future wheat breeding programmes.…”

Pyramiding Bacterial Blight Resistance Genes in Tainung82 for Broad-Spectrum Resistance Using Marker-Assisted Selection

“…The four BC 2 F 2 plants carrying five positive homozygous alleles of the donor genes, including Xa4, xa5, Xa7, xa13 and Xa21, were screened from 5012 BC 2 F 2 plants. Four BC 2 F 2 plants showed recurrent genome content of TNG82 with %RPG of 92.05% (29), 84.3% (18), 83.1% (5) and 79.4% (43), with an average of 84.71% (Table S1). In the BC 2 F 3 generation, 17 plants containing different BB resistance genes were used to confirm resistance reaction by inoculation with Xoo isolate XF89-b and evaluated for agronomic performance.…”

“…Recently, xa5, xa13 and Xa21 genes were introgressed into the hybrid rice maintainer lines CO2B, BO23B and CO24B through MAS, which can form the basis to develop new, widely adaptable heterotic hybrids possessing resistance against the destructive diseases to which rice is vulnerable [17]. In addition, there have been several examples of MAS being utilized to successfully incorporate different genes which provide higher resistance to various biotic and abiotic stresses (for example, the pyramiding of QTLs of submergence tolerance (Sub1A), leaf/neck blast (qBL1 and qBL11), brown planthopper (Bph3) and BB (xa5 and Xa21) in high-yielding and aromatic rice variety 'Pink3 [18]).…”

Identification of novel major and minor QTLs associated with Xanthomonas oryzae pv. oryzae (African strains) resistance in rice (Oryza sativa L.)

“…Most of the BB R genes provide complete race-specific resistance to Xoo strains. Different combinations of Xa4, xa5, Xa7, xa13 and Xa21 have been incorporated in popular rice commercial varieties in different countries in Asia (Century et al 1999 ; Singh et al 2006 ; Swamy et al 2006 ; Perez et al 2008 ; Sundaram et al 2009 , Shanti 2010 ; Suh et al 2013 ; Ruengphayak et al 2015 ). Few examples indicate that some R genes used for controlling BB disease are overcome by virulent strains as shown in Korea with the resistant gene Xa21 (Lee et al 1999 ; Zhang et al 2006 ).…”