Incomplete block designs for genetic testing: accuracy for ranking families and individuals
2000
Fu, Yong-Bi | Namkoong, G. (University of British Columbia, Vancouver (Canada). Department of Forest Sciences) | Yanchuk, A.D.
A randomized incomplete block design (ICB) can increase the precision of estimating family means on heterogeneous test sites and consequently increase the probability of having an accurate ranking of families, but the magnitude of the increase in the probability compared with a randomized complete block design (RCB) has been less clear. To address this issue, a stochastic computer simulation of a full-sib progeny trial with 90 families of 10 seedlings per family was conducted on a test site varying with patchiness and gradients in environmental effects and assuming a range of heritabilities. Seedlings were laid out following both RCB and ICB with single-tree plots. Family means were estimated and combined family plus individual selection indices based on estimated genetic parameters were applied for individual trees. Kendall's coefficient of concordance was used to measure the degree of agreement between the true and estimated ranks. Results from the simulation showed that the individual heritability, rather than the block design, had the main impact on the accuracy of ranking both the families and individuals. The higher the true heritability, the more accurate the estimated ranking. Both designs showed a slight increase in accuracy of ranking with increased patchiness and gradients of environmental effects. Generally, ICB showed a slight superiority over RCB in ranking accuracy. The ranking of families was more accurate than ranking of individuals
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