“Types of Mating Designs Used in Quantitative Genetic Analysis”

UNIVERSITY OF AGRICULTURAL SCIENCES, BANGALORE

DEPARTMENT OF GENETICS AND PLANT BREEDING

M.Sc. Seminar – GPB 628 (0+1)

“Types of Mating Designs Used in Quantitative Genetic Analysis”

In plant breeding, the selection of suitable parents and mating designs is critical for successful crop improvement. The choice of a mating design depends on the study’s objectives, available resources, time, space, cost, and biological constraints. Various mating designs include Polycross, Topcross, North Carolina designs (I, II, III), Diallel, Partial diallel, Triple Test Cross (TTC), and Line × Tester design. These designs involve crossing individuals randomly to produce progenies related as half-sibs or full-sibs, each varying in complexity and purpose¹.

The diallel mating design involves crossing all possible parent combinations. Griffing (1956) developed four diallel methods widely used for analyzing additive and non-additive genetic effects. Hayman’s diallel model provides detailed genetic variance information. Partial diallel mating (Kempthorne & Curnow, 1961) reduces complexity by limiting crosses while increasing the number of parents. Cockerham (1961) extended diallel concepts through triallel and quadrallel hybrids to estimate variances among multi-way crosses².

The topcross design (Jenkins & Brunsen, 1932) involves crossing multiple female inbreds with a single male tester, typically an F1 hybrid, for early combining ability evaluation. The line × tester design (Kempthorne, 1957) crosses lines with wide-based testers in all combinations to produce one-to-one F1 hybrids, allowing efficient assessment of combining ability. Polycross design allows natural crossing of cultivars in isolated blocks, maintaining heterozygosity, and is well suited for obligate cross-pollinating species².

North Carolina designs, developed by Comstock and Robinson (1948), are powerful tools for genetic variance estimation. NCD I crosses each male with different females to create half- and full-sib families, estimating additive and dominance gene effects. NCD II employs factorial crosses of all males with all females, estimating both general combining ability (GCA) and specific combining ability (SCA), but requires more resources. NCD III backcrosses males from an F₂ population to original female parents to study dominance effects². The Triple Test Cross (Kearsey and Jinks, 1968) and its subsequent modifications are among the most effective designs for analyzing the genetic architecture of randomly mating populations³.

Overall, breeders must carefully select mating designs based on resources and study goals to ensure accurate genetic analysis and effective progeny generation.

REFERENCES

1. Nduwumuremyi, A., Tongoona, P. and Habimana, S., 2013. Mating designs: helpful tool for quantitative plant breeding analysis. Int. J. Plant Breed. Genet., 1(3): 117-129.

2. Awata, L.A., Tongoona, P., Danquah, E., Efie, B.E. and Marchelo-Dragga, P.W., 2018. Common mating designs in agricultural research and their reliability in estimation of genetic parameters. IOSR J. Agric. Vet. Sci., 11(7): 16-36.

3. Pooni, H.S. and Jinks, J.L., 1976. The efficiency and optimal size of triple test cross designs for detecting epistatic variation. Heredity, 36(2): 215-227.