Plant & Animal Genome V Conference
Town & Country Hotel, San Diego, CA, January 12-16, 1997.
PAG-V: W3 - MARKER-ASSISTED SELECTION FOR IMPROVING DROUGHT TOLERANCE IN TROPICAL MAIZE LINES
W3
MARKER-ASSISTED SELECTION FOR IMPROVING DROUGHT TOLERANCE IN TROPICAL MAIZE LINES
RIBAUT, JEAN-MARCEL, Diego Gonzalez-de-Leon, Changjian Jiang, Xueyi Hu, Javier Betran, David Hoisington
CIMMYT, Int., Lisboa 27, Apdo. P. 6-641, Mexico D.F. 06600, Mexico
A few years ago, a project for drought improvement of tropical maize lines through molecular markers was initiated at CIMMYT. The first step was a "classical" quantitative trait locus (QTL) study to identify genomic regions involved in the expression of yield components and secondary traits of interest. Specific attention was given to anthesis-silking interval (ASI), used by breeders as a very good indicator of drought tolerance in maize. Based on the characteristics of the QTL identified for several traits, principally their stability across water regimes and their putative effect on the phenotypic variance, we arrived to the following conclusion: a marker-assisted selection (MAS) scheme based on yield QTL alone, or QTL of secondary traits alone (such as ASI), is not the most efficient for increasing yield under drought. We therefore recommend a MAS strategy based on a combination of the "best QTL" for different traits, directly or indirectly related with yield. A MAS backcross experiment to improve drought tolerance in an elite CIMMYT maize line is in progress at CIMMYT, based on the transfer of five selected QTL. Various logistical aspects of this work and its results will be presented in detail, with special attention given to the use of reliable PCR-based markers in the "preselection" steps. The use of these markers allows to increase substantially the pressure of selection at each backcross step, thus making the selection process more efficient by reducing the number of backcross cycles. Suitable PCR-based markers also open attractive perspectives for new MAS strategies that will be outlined.