Locating genes associated with root morphology and drought avoidance in rice via linkage to molecular markers

Abstract

This research was undertaken to identify and map quantitative trait loci (QTLs) associated with five parameters of rice root morphology and to determine if these QTLs are located in the same chromosomal regions as QTLs associated with drought avoidance/tolerance. Root thickness, root:shoot ratio, root dry weight per tiller, deep root dry weight per tiller, and maximum root length were measured in three replicated experiments (runs) of 203 recombinant inbred lines grown in a greenhouse. The lines were from a cross between indica cultivar Co39 andjaponica cultivar Moroberekan. The 203 RI lines were also grown in three replicated field experiments where they were drought-stressed at the seedling, early vegetative, and late-vegetative growth stage and assigned a visual rating based on leaf rolling as to their degree of drought avoidance/tolerance. The QTL analysis of greenhouse and field data was done using single-marker analysis (ANOVA) and interval analysis (Mapmaker QTL). Most QTLs that were identified were associated with root thickness, root/shoot ratio, and root dry weight per tiller, and only a few with deep root weight. None were reliably associated with maximum root depth due to genotype-by-experiment interaction. Root thickness and root dry weight per tiller were the characters found to be the least influenced by environmental differences between greenhouse runs. Correlations of root parameters measured in greenhouse experiments with field drought avoidance/tolerance were significant but not highly predictive. Twelve of the fourteen chromosomal regions containing putative QTLs associated with field drought avoidance/tolerance also contained QTLs associated with root morphology. Thus, selecting for Moroberekan alleles at marker loci associated with the putative root QTLs identified in this study may be an effective strategy for altering the root phenotype of rice towards that commonly associated with drought-resistant cultivars.

Natural variation of rice strigolactone biosynthesis is associated with the deletion of two MAX1 orthologs

“…Indeed, tillering mapped to the same SL locus on chromosome 1. Interestingly, in previous QTL studies using an IR64-Azucena and the BalaAzucena mapping populations, several root architectural traits were mapped in the same region, suggesting that they may also be controlled by this locus (37,38). These findings emphasize the potential of qSLB1.1 for the improvement of important agronomic traits in rice.…”

Rice Root Genetic Architecture: Meta-analysis from a Drought QTL Database

“…At least 24 papers have been published in the last 10 years on quantitative trait locus (QTL) detection for a large number of root parameters in several populations and different growth conditions (Champoux et al 1995;Ray et al 1996;Redona and Mackill 1996;Yadav et al 1997;Price et al 1999Price et al , 2000Price et al , 2002Ali et al 2000;Hemamalini et al 2000;Tripathy et al 2000;Zheng et al 2000Zheng et al , 2003Shen et al 2001;Zhang et al 2001a, b;Kamoshita et al 2002a, b;Courtois et al 2003;Nguyen et al 2004;Xu et al 2004;Li et al 2005b;Horii et al 2006;Yue et al 2006;MacMillan et al 2006).…”

Quantitative trait loci associated with stomatal conductance, leaf rolling and heading date mapped in upland rice (Oryza sativa)

“…Molecular mapping of root growth QTLs has been published in three different populations (Champoux et al, 1995, Ray et al,1996Redona & Mackill, 1996; and these results show that, although many root grow^th QTLs are specific to each report, some are common to two or three crosses and environments.…”