Marker-assisted backcrossing: a useful method for rice improvement

Abstract

The world's population is increasing very rapidly, reducing the cultivable land of rice, decreasing table water, emerging new diseases and pests, and the climate changes are major issues that must be addressed to researchers to develop sustainable crop varieties with resistance to biotic and abiotic stresses. However, recent scientific discoveries and advances particularly in genetics, genomics and crop physiology have opened up new opportunities to reduce the impact of these stresses which would have been difficult if not impossible as recently as the turn of the century. Marker assisted backcrossing (MABC) is one of the most promising approaches is the use of molecular markers to identify and select genes controlling resistance to those factors. Regarding this, MABC can contribute to develop resistant or high-yielding or quality rice varieties by incorporating a gene of interest into an elite variety which is already well adapted by the farmers. MABC is newly developed efficient tool by which using large population sizes (400 or more plants) for the backcross F1 generations, it is possible to recover the recurrent parent genotype using only two or three backcrosses. So far, many high yielding, biotic and abiotic stresses tolerance, quality and fragrance rice varieties have been developed in rice growing countries through MABC within the shortest timeframe. Nowadays, MABC is being used widely in plant breeding programmes to develop new variety/lines especially in rice. This paper reviews recent literature on some examples of variety/ line development using MABC strategy.

Genetic analysis and identification of SSR markers associated with rice blast disease in a BC₂F₁ backcross population

“…These results agree with the findings by Tanweer et al (2015a), who identified the Pi-kh gene using RM206. Likewise, Hasan et al (2015) and Ashkani et al (2013) identified Pi-7(t) using RM5961 and PS2 as the donor parent. Our results are further supported by Tanweer et al (2015b) who suggested that PS2 consisted to 23% of the Pi-kh resistance gene on different chromosome locations.…”

“…Unfortunately, biotic and abiotic stresses have become a limiting factor for rice production (Hasan et al, 2015). Blast disease caused by the hemi-biotroph fungus Magnaporthe oryzae (teleomorph) or Pyricularia grisea (anamorph) has been ranked the primary threat to rice productivity (Skamnioti and Gurr, 2009).…”

Identification, Mapping and Pyramiding of Genes/Quantitative Trait Loci (QTLs) for Durable Resistance of Crops to Biotic Stresses

“…These include Restriction Fragment Length Polymorphisms (RFLPs), Random Amplification of Polymorphic DNAs (RAPDs), Amplified Fragment Length Polymorphisms (AFLPs), Simple Sequence Repeats (SSRs) or microsatellites, inter-SSRs (ISSRs), and most recently single nucleotide polymorphism (SNP) [14,68]. It is beyond the scope of this review to discuss the technical methods of how each of these DNA markers is functioning.…”

“…During backcrossing, together with the target gene, some unwanted genomic regions (gene drag) of the donor parent can transfer into the backcross progenies. Removing the linkage drag and recovering the recurrent parent genome requires six to eight backcrossing [67]. At each backcross generation, the proportion of recurrent parent genome recovered could be estimated using the formula 1−(1/2) n+1 , where n is the number of backcross generations.…”

“…The second level of selection is called recombination selection where homozygous alleles of the recurrent parent will be selected using tightly liked markers flanking the target alleles. This step is important to reduce linkage drag [67]. The third level of selection is called the background selection which involves the selection of individuals carrying homozygous alleles of the recurrent parent at a number of unlinked marker loci covering the entire genome (chromosome 2, 3 and 4 in Figure 9 in background selection) [59].…”