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Abstract
BackgroundEarlier studies were focused on the genetics of temperate and tropical maize under drought. We identified genetic loci and their association with functional mechanisms in 240 accessions of subtropical maize using a high-density marker set under water stress.ResultsOut of 61 significant SNPs (11 were false-discovery-rate-corrected associations), identified across agronomic traits, models, and locations by subjecting the accessions to water stress at flowering stage, 48% were associated with drought-tolerant genes. Maize gene models revealed that SNPs mapped for agronomic traits were in fact associated with number of functional traits as follows: stomatal closure, 28; flowering, 15; root development, 5; detoxification, 4; and reduced water potential, 2. Interactions of these SNPS through the functional traits could lead to drought tolerance. The SNPs associated with ABA-dependent signalling pathways played a major role in the plant’s response to stress by regulating a series of functions including flowering, root development, auxin metabolism, guard cell functions, and scavenging reactive oxygen species (ROS). ABA signalling genes regulate flowering through epigenetic changes in stress-responsive genes. ROS generated by ABA signalling are reduced by the interplay between ethylene, ABA, and detoxification signalling transductions. Integration of ABA-signalling genes with auxin-inducible genes regulates root development which in turn, maintains the water balance by regulating electrochemical gradient in plant.ConclusionsSeveral genes are directly or indirectly involved in the functioning of agronomic traits related to water stress. Genes involved in these crucial biological functions interacted significantly in order to maintain the primary as well as exclusive functions related to coping with water stress. SNPs associated with drought-tolerant genes involved in strategic biological functions will be useful to understand the mechanisms of drought tolerance in subtropical maize.Electronic supplementary materialThe online version of this article (doi:10.1186/1471-2164-15-1182) contains supplementary material, which is available to authorized users.
Highlights
Earlier studies were focused on the genetics of temperate and tropical maize under drought
The panel was phenotyped for anthesis-to-silking interval (ASI), ear length (EL), ear girth (EG), kernels per row (KR), the number of kernel rows (KRN), 100-kernel weight (HKW), and grain yield (GY) at three locations: Indian Agriculture Research Institute (IARI), New Delhi; Acharya N G Ranga Agricultural University (ANGRAU), Hyderabad; and Agricultural Research Station (ARS), Karimnagar for two years
The phenotypic correlation coefficient showed that GY and the traits contributing to it were positively and significantly correlated with each other, and ASI was negatively but significantly correlated with other agronomic traits [Additional file 2: Table S2]
Summary
Earlier studies were focused on the genetics of temperate and tropical maize under drought. A shorter anthesis-to-silking interval (ASI) was observed under drought in a lowland tropical maize population [2], and the interval was considered to be an indirect selection criterion for grain yield [3]. Several researchers have identified drought-related genes in different tissues that regulate molecular and physiological responses under stress [6,7,8]. In the ears and silks of maize, some genomic regions that control the levels of abscisic acid (ABA) and sugar showed the signal transduction involved in stress-related pathways and regulated kernel size and productivity of the plant under drought [6]. Different tissues showed the expression of an NAC-transcription-factor-encoding gene [9], which was observed to be strongly associated with the relative ear position, 100-kernel weight, and flowering time across the experimental maize population [10]. Some drought response has been recorded recently in reproductive and leaf meristem tissues in maize [7]
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