Biology Reference
In-Depth Information
Chapter 4
Marker-Assisted Introgression of Major QTLs
for Grain Yield Under Drought inRice
ArvindKumar,ShalabhDixit,and AmeliaHenry
Abstract
Developing rice for drought tolerance has been one of the greatest challenges in the field of rice
breeding. Several selection criteria based on morpho-physiological traits have been used in the past to
identify drought-tolerant rice genotypes, quantitative trait loci (QTL), and genes. However, the success
of these methods, in terms of adopting them into conventional and molecular breeding programs, has
been limited. Recent studies have shown the effectiveness of screening rice genotypes for grain yield
under drought stress for the development of drought-tolerant varieties. It has been observed that
screening rice lines in the field under both managed drought stress and non-stress conditions provides
an opportunity for combining high-yield potential with drought tolerance. The success of these
screening strategies has led to the development and release of several drought-tolerant lines with high
yield under non-stress conditions. Genotyping strategies such as bulk segregant analysis (BSA) and
selective genotyping (SG) have been used to handle large populations derived from multiple donors and
recipients. Several large-effect QTLs for increased grain yield under drought stress with consistent
performance across multiple genetic backgrounds have been detected through the combination of
screening for grain yield under drought and these genotyping strategies. The drought-yield QTLs
have shown promising results in terms of their effect under a wide range of environments and are
being successfully utilized in marker-assisted selection (MAS) programs. Physiological analysis of
near-isogenic lines with these QTLs has revealed novel drought-related traits such as increased lateral
roots and decreased xylem vessel diameter. Detection and pyramiding of such large-effect QTLs with
genes for tolerance to other biotic stresses in the background of widely adapted cultivars can be an
efficient strategy for increasing productivity of rice in rain-fed areas.
Introduction
torily with limited water supply or under peri-
odic conditions of water deficit (Turner 1979).
Crop plants do not need to simply survive under
drought, but should also possess the ability to
Drought Tolerance: Complex or Simple?
Drought tolerance is defined as the ability of
a plant to live, grow, and reproduce satisfac-
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