title: Molecular mapping across three populations reveals a QTL hotspot region on chromosome 3 for secondary traits associated with drought tolerance in tropical maize.
abstract: 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 morpho-physiological traits considered in the current study. This region contained two important candidate genes viz.,zmm16(MADS-domain transcription factor) andpsbs1(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.
authors: Universidade Federal de Viçosa (UFV), CEP: 36.570-000 Viçosa, Minas Gerais State Brazil ; Monsanto Company, CEP: 38.405-232 Uberlândia, Minas Gerais Brazil.
authors: Gustavo Dias
authors: GD
authors: Almeida
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Sudha
authors: S
authors: Nair
authors: Universidade Federal de Viçosa (UFV), CEP: 36.570-000 Viçosa, Minas Gerais State Brazil.
authors: Aluízio
authors: A
authors: Borém
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Jill
authors: J
authors: Cairns
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Samuel
authors: S
authors: Trachsel
authors: Generation Challenge Program, Hosted by CIMMYT, Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Jean-Marcel
authors: JM
authors: Ribaut
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Marianne
authors: M
authors: Bänziger
authors: CIMMYT, ICRAF House, United Nations Avenue, Gigiri, Nairobi, 00621 Kenya.
authors: Boddupalli M
authors: BM
authors: Prasanna
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Jose
authors: J
authors: Crossa
authors: International Maize and Wheat Improvement Center (CIMMYT), Apdo. Postal 6-641, Mexico, DF Mexico.
authors: Raman
authors: R
authors: Babu
keywords: Drought tolerance; MetaQTL; SNP; Secondary traits