Combined detection and introgression of QTL underlying desirable traits

¹ Department of Animal & Aquacultural Sciences, Norwegian University of Life Sciences, N-1432 Ås, Norway
² AKVAFORSK, P.O.Box 5010, 1432 Ås, Norway
³ Department of Animal & Aquacultural Sciences, Norwegian University of Life Sciences, N-1432 Ås, Norway; Roslin Institute, Roslin, Midlothian, EH25 9PS, Scotland

^* To whom correspondence should be addressed. E-mail: hossein.yazdi{at}umb.no.

	Abstract

This study presents a new method that combines QTL mapping and gene introgression. The effectiveness of this method for simultaneous detection and introgression of a desirable QTL from a donor line into a recipient line was evaluated by simulation. For evaluation we used the fourth backcross generation of 2 inbred lines. The difference between the 2 lines for the trait of interest was described entirely by 1 QTL with the donor line carrying the superior allele. Nine different scenarios, combinations of 3 heritabilities h² = 0.10, 0.05 or 0.01, and 3 population sizes N=100, 500 or 1000, were considered in the simulation. Selection of parents for the next backcross was based solely upon the estimated probability of carrying the superior allele after a QTL analysis. Estimates of the QTL location and allele substitution effect in most scenarios were comparable to the true values. However, with either small h² or N, the QTL allele substitution effect was underestimated and location was also biased. The standard error of the estimates decreased with increasing N. The retained donor chromosome segment and linkage drag were close to the expected values for other published work. In general, combined detection and introgression of genes underlying desirable traits not only saves at least 1 generation, but also it ensures that the desirable QTL is introgressed where its function is simultaneously tested in a planned environment and recipient genome structure.

Key Words: backcross design, inbred lines, introgression, QTL mapping