Molecular mapping across three populations reveals a QTL hotspot region on chromosome 3 for secondary traits associated with drought tolerance in tropical maize
Gustavo Dias Almeida
0
1
2
3
4
Sudha Nair
0
1
2
3
4
Aluzio Borem
0
1
2
3
4
Jill Cairns
0
1
2
3
4
Samuel Trachsel
0
1
2
3
4
Jean-Marcel Ribaut
0
1
2
3
4
Marianne Ba nziger
0
1
2
3
4
Boddupalli M. Prasanna
0
1
2
3
4
Jose Crossa
0
1
2
3
4
Raman Babu
0
1
2
3
4
0
S. Nair J. Cairns S. Trachsel M. Banziger J. Crossa R. Babu (&) International Maize and Wheat Improvement Center (CIMMYT)
, Apdo. Postal 6-641,
Mexico
, DF,
Mexico
1
G. D. Almeida Monsanto Company, CEP: 38.405-232 Uberlandia, Minas Gerais,
Brazil
2
G. D. Almeida A. Borem Universidade Federal de Vicosa (UFV)
, CEP: 36.570-000 Vicosa, Minas Gerais State,
Brazil
3
B. M. Prasanna CIMMYT, ICRAF House,
United Nations Avenue
, Gigiri, Nairobi 00621,
Kenya
4
J.-M. Ribaut Generation Challenge Program
, Hosted by CIMMYT, Apdo. Postal 6-641,
Mexico
, DF,
Mexico
Identifying quantitative trait loci (QTL) of sizeable effects that are expressed in diverse genetic backgrounds across contrasting water regimes particularly for secondary traits can significantly complement the conventional drought tolerance breeding efforts. We evaluated three tropical maize biparental populations under water-stressed and well-watered regimes for drought-related morpho-physiological traits, such as anthesis-silking interval (ASI), ears per plant (EPP), stay-green (SG) and plant-to-ear height ratio (PEH). In general, drought stress reduced the genetic variance of grain yield (GY), while that of morpho-physiological traits remained stable or even increased under drought conditions. We detected consistent genomic regions across different genetic backgrounds that could be target regions for marker-assisted introgression for drought tolerance in maize. A total of 203 QTL for ASI, EPP, SG and PEH were identified under both the water regimes. Meta-QTL analysis across the three populations identified six constitutive genomic regions with a minimum of two overlapping traits. Clusters of QTL were observed on chromosomes 1.06, 3.06, 4.09, 5.05, 7.03 and 10.04/06. Interestingly, a *8-Mb region delimited in 3.06 harboured QTL for most of the morphophysiological traits considered in the current study. This region contained two important candidate genes viz., zmm16 (MADS-domain transcription factor) and psbs1 (photosystem II unit) that are responsible for reproductive organ development and photosynthate accumulation, respectively. The genomic regions identified in this study partially explained the association of secondary traits with GY. Flanking single nucleotide polymorphism markers reported herein may be useful in marker-assisted introgression of drought tolerance in tropical maize.
-
Maize (Zea mays L.) is an important economic crop and,
due its high yield potential, is currently recognised as a
major crop that can ensure food security worldwide.
Water scarcity is the most important environmental
limiting factor for maize productivity in tropical and
subtropical regions (Messmer et al. 2011). It has been
projected that by the year 2050, a 70 % increase in
global food production must occur, while the global
climate change scenario tends to increase the problems
of food insecurity (Varshney et al. 2010). This grim
forecast has forced plant scientists to breed cultivars that
can be grown in marginal areas with limited water
availability. The genetic improvement for water stress
tolerance can ensure sustainable and long-term benefits,
especially when combined with improved agronomic
techniques (Duvick 2005). Drought stress can adversely
affect many aspects of maize physiological metabolism
and growth, including photosynthesis, plant height, dry
matter production, leaf area and grain yield (Ge et al.
2012). Plants undergo various morphological,
biochemical and physiological changes to respond and adapt in
order to survive under drought stress (Lu et al. 2011).
Increasing grain yield (GY) is the primary objective
of breeding for drought tolerance; however, direct
selection for GY under water scarcity has generally led
to limited progress and stability owing to the reduction
in the genotypic variance of GY under drought stress
conditions. Secondary/morpho-physiological traits
that are correlated with drought tolerance can
experience increased genetic variance and heritability
under stress conditions (Tuberosa et al. 2002). It has
been demonstrated that some secondary traits, such as
anthesis-silking interval (ASI), ears per plant (EPP),
plant height (PH) and stay-green (SG) traits (leaf
senescence and chlorophyll contents), are correlated
with drought responses and remain stable under
drought stress or might even exhibit enhanced genetic
variance (Bolanos and Edmeads 1996; Betran et al.
2003; Messmer et al. 2009; Lu et al. 2011; Messmer
et al. 2011). Thus, these traits are considered useful to
improve selection efficiency for drought tolerance and
accordingly their use has been suggested for the
improved tolerance of maize to drought and low
nitrogen conditions (Banzinger and Lafitte 1997;
Banzinger (...truncated)