Practice question

Plant breeding is defined as art and science that genetically improves crops to meet human requirements for food, feed, fiber, fuel, and aesthetic purposes. As science it draws upon Mendelian genetics describing segregation and independent assortment, population and quantitative genetics estimating heritability and gain from selection, cytogenetics understanding chromosome behavior and polyploidy, molecular genetics including marker assisted selection using SSRs and SNPs, and biotechnology employing transgenesis and genome editing tools CRISPR-Cas9. As art it involves breeder intuition, experience in phenotypic selection of desirable types, choice of parental combinations based on combining ability, handling of segregating generations, and adaptation to target environments through multi-location trials. Breeding objectives include higher yield via heterosis and improved harvest index, quality traits such as protein and oil content, resistance to biotic stresses conferred by R genes and quantitative trait loci, tolerance to abiotic stresses including drought mediated by DREB transcription factors, and adaptation to mechanization. Successful cultivar must be distinct, uniform, and stable under seed certification.