Reference "Genetic dissection of an elite rice hybrid revealed that heterozygotes are not always advantageous for performance"

Reference ID

7756

Title

Genetic dissection of an elite rice hybrid revealed that heterozygotes are not always advantageous for performance

Source

Genetics, 2002, vol. 162, pp. 1885-1895

Authors (6)

Hua-J-P	Xing-Y-Z
Xu-C-G	Sun-X-L
Yu-S-B	Zhang-Q

Abstract

We introduced an experimental design that produced an "immortalized F(2)"
population allowing for complete dissection of genetic components underlying
quantitative traits. Data for yield and three component traits of the
immortalized F(2) were collected from replicated field trials over 2 years.
Using 231 marker loci, we resolved the genetic effects into individual
components and assessed relative performance of all the genotypes at both single-
and two-locus levels. Single-locus analysis detected 40 QTL for the four traits.
Dominance effects for about one-half of the QTL were negative, resulting in
little "net" positive dominance effect. Correlation between genotype
heterozygosity and trait performance was low. Large numbers of digenic
interactions, including AA, AD, and DD, were detected for all the traits, with
AA as the most prevalent interaction. Complementary two-locus homozygotes
frequently performed the best among the nine genotypes of many two-locus
combinations. While cumulative small advantages over two-locus combinations may
partly explain the genetic basis of heterosis of the hybrid as double
heterozygotes frequently demonstrated marginal advantages, double heterozygotes
were never the best genotypes in any of the two-locus combinations. It was
concluded that heterozygotes were not necessarily advantageous for trait
performance even among genotypes derived from such a highly heterotic hybrid.