Introgression of Maize Diversity for Drought Tolerance: Subtropical Maize Landraces as Source of New Positive Variants

Abstract

Current climate change models predict an increased frequency and intensity of drought for much of the developing world within the next 30 years. These events will negatively affect maize yields, potentially leading to economic and social instability in many smallholder farming communities. Knowledge about the genetic resources available for traits related to drought tolerance has great importance in developing breeding program strategies. The aim of this research was to study a maize landrace introgression panel to identify chromosomal regions associated with a drought tolerance index. For that, we performed Genome-Wide Association Study (GWAS) on 1326 landrace progenies developed by the CIMMYT Genetic Resources Program, originating from 20 landraces populations collected in arid regions. Phenotypic data were obtained from early testcross trials conducted in three sites and two contrasting irrigation environments, full irrigation (well-watered) and reduced irrigation (drought). The populations were genotyped using the DArTSeq® platform, and a final set of 5,695 SNPs markers was used. The genotypic values were estimated using spatial adjustment in a two-stage analysis. First, we performed the individual analysis for each site/irrigation treatment combination. The best linear unbiased estimates (BLUEs) were used to calculate the Harmonic Mean of Relative Performance (HMRP) as a drought tolerance index for each testcross. The second stage was a joint analysis, which was performed using the HMRP to obtain the best linear unbiased predictions (BLUPs) of the index for each genotype. Then, GWAS was performed to determine the marker-index associations and the marker-Grain Yield (GY) associations for the two irrigation treatments. We detected two significant markers associated with the drought-tolerance index, four associated with GY in drought condition, and other four associated with GY in irrigated conditions each. Although each of these markers explained less than 0.1% of the phenotypic variation for the index and GY, we found two genes likely related to the plant response to drought stress. For these markers, alleles from landraces provide a slightly higher yield under drought conditions. Our results indicate that the positive diversity delivered by landraces are still present on the backcrosses and this is a potential breeding strategy for improving maize for drought tolerance and for trait introgression bringing new superior allelic diversity from landraces to breeding populations.

Identification of Genomic Regions Associated with Agronomic and Disease Resistance Traits in a Large Set of Multiple DH Populations

“…Due to the inclusion of DH lines derive from crosses of selected inbred lines in the panel, we observed moderate structure in the present study. Several researchers also been reported moderate structure in the tropical maize germplasm [ 29 , 31 , 37 , 53 , 54 , 60 ].…”

“…Semagn et al [ 2 ] reported four meta-QTLs associated with grain yield for both under drought and optimum management. The high QTL detection power and fine resolution of mapping are exploited by joint linkage association mapping in multiple biparental populations [ 28 , 29 , 30 ]. The identification and validation of novel genomic regions associated with economically important traits under WW and WS as well as MLN are important to accelerate the development of climate-resilient improved maize varieties to enhance high maize productions in smallholder families and contribute to food security [ 12 , 31 , 32 ].…”

Assessment of Nitrogen Use Efficiency in Algerian Saharan Maize Populations for Tolerance under Drought and No-Nitrogen Stresses

“…There is no doubt that the landraces are adapted to a specific environment and region [91]. Furthermore, the main reason to use landraces is to bring novel favorable alleles to a breeding population [92]. The local landraces are rich in diverse genetic materials and are a good source of important genes such as resistance to biotic and abiotic stresses and quality traits [91] and have a better capacity to absorb and utilize N under low N fertilization conditions [93].…”

“…However, the improvement of NUE in maize cultivars is a great challenge due to the genetic complexity and strong interaction with the environment. Thus, information on the genetic control governing the inheritance of traits would be useful for crop researchers to choose the breeding method for obtaining NUE efficient cultivars [20] and to develop breeding program strategies for traits related to drought tolerance [92]. Therefore, assessment of combining ability and heterosis is of utmost importance for breeding hybrid maize [112], so that the genotypes could be successfully used to develop hybrids with superior NUE under diverse environmental conditions.…”

Genome-Wide Association Study Reveals Genetic Architecture and Candidate Genes for Yield and Related Traits under Terminal Drought, Combined Heat and Drought in Tropical Maize Germplasm

“…Heat stress is reported to prolong the anthesis–silking interval, reduce kernel set [ 9 , 10 , 19 , 20 ], decrease photosynthetic rate and chlorophyll content [ 14 , 19 , 21 ], and lead to damaged cellular membrane [ 22 ]. Conversely, drought and or terminal drought at seedling stage has deleterious impacts on seedling establishment, vegetative growth, photosynthesis, root growth, anthesis, anthesis–silking interval, pollination, and grain formation in maize [ 23 , 24 ]. Combined heat and drought is well documented to reduce photosynthetic efficiency, stomatal conductance, leaf area, water use efficiency, and ultimately grain reduction [ 25 , 26 ].…”