Briefly describe any two of these schemes and discuss their usefulness in crop improvement.

Two breeding schemes that make full use of molecular marker data are Marker-Assisted Backcrossing (MABC) and Genomic Selection (GS).

Marker-Assisted Backcrossing (MABC):

·         MABC is a breeding scheme designed to introgress target genes or genomic regions from a donor parent into an elite or recurrent parent while minimizing the transfer of undesirable genetic material. Molecular markers linked to the target trait or gene are used to select individuals with the desired allele(s) during backcrossing.

·         Usefulness in Crop Improvement: MABC is particularly useful for breeding programs targeting specific traits of interest, such as disease resistance, abiotic stress tolerance, or quality traits. It allows breeders to introgress target genes or alleles into elite germplasm rapidly and efficiently while retaining the genetic background of the recurrent parent. MABC accelerates the development of improved cultivars with enhanced performance and resilience by combining the favorable traits of the donor parent with the elite genetic background of the recurrent parent.

Genomic Selection (GS):

·         GS is a breeding scheme that uses genome-wide molecular marker data to predict the genetic merit of individuals for complex traits. Statistical models are trained using marker data and phenotypic information from a training population to estimate genomic estimated breeding values (GEBVs) for selection candidates.

·         Usefulness in Crop Improvement: GS is well-suited for breeding programs targeting complex traits with low heritability or controlled by many small-effect loci, such as yield, drought tolerance, or nutritional quality. GS enables breeders to predict the genetic potential of individuals based on their genomic profiles, allowing for selection decisions to be made at early stages of the breeding cycle. GS accelerates genetic gain by enabling the selection of superior individuals with high GEBVs, leading to the development of improved cultivars with enhanced performance and productivity.

In summary, Marker-Assisted Backcrossing (MABC) and Genomic Selection (GS) are two breeding schemes that leverage molecular marker data to accelerate crop improvement. MABC facilitates the introgression of target genes into elite germplasm, while GS enables the prediction of genetic merit for complex traits, both leading to the development of improved cultivars with desirable traits and enhanced performance. These breeding schemes enhance breeding efficiency, precision, and genetic gain, contributing to sustainable crop improvement and food security.