Genetics. Published Articles Ahead of Print: March 4, 2007, Copyright © 2007
doi:10.1534/genetics.106.064493


A more recent version of this article appeared on May 1, 2007.

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Classical genetic and QTL analyses of heterosis in a maize hybrid between two elite inbred lines

Elisabetta Frascaroli 1*, Maria Angela Canè 1, Pierangelo Landi 1, Giorgio Pea 2, Luca Gianfranceschi 2, Marzio Villa 2, Michele Morgante 3 and Mario Enrico Pè 2

1 University of Bologna
2 University of Milan
3 University of Udine

* To whom correspondence should be addressed. E-mail: elisabetta.frascaroli{at}unibo.it.

Submitted on October 10, 2006
Revised on December 1, 2006
Accepted on 17 February 2007


Abstract

The exploitation of heterosis is one of the most outstanding advancements in plant breeding, though its genetic basis is not well understood yet. This research was conducted on the materials arising from the maize single cross B73 X H99 to study heterosis by procedures of classical genetic and QTL analyses. Materials were the basic generations, the derived 142 recombinant inbred lines (RILs) and the three testcross populations obtained crossing the 142 RILs to each parent and their F1. For seedling weight (SW), number of kernels per plant (NK) and grain yield (GY) heterosis was greater than 100% and the average degree of dominance was superior to one. Epistasis was significant for SW and NK but not for GY. Several QTLs were identified and they were prevailingly in the additive-dominance range for traits with low heterosis and prevailingly in the dominance-overdominance range for plant height (PH), SW, NK and GY. Only few QTLs with digenic epistasis were identified. The importance of dominance effects was confirmed by highly significant correlations between heterozygosity level and phenotypic performance, especially for GY. Some chromosome regions presented overlaps of overdominant QTLs for SW, PH, NK and GY, suggesting pleiotropic effects on the overall plant vigor.

Key Words: Hybrid vigor, Zea mays L., design III, dominance ratio, quantitative trait loci




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