Abstract Background Identification of QTL with large phenotypic effects conserved across genetic backgrounds and environments is one of the prerequisites for crop improvement using marker assisted selection MAS. The objectives of this study were to identify meta-QTL mQTL for grain yield GY and anthesis silking interval ASI across 18 bi-parental maize populations evaluated in the same conditions across managed water stressed and well watered environments.
This article has been cited by other articles in PMC. Abstract Background Identification of QTL with large phenotypic effects conserved across genetic backgrounds and environments is one of the prerequisites for crop improvement using marker assisted selection MAS.
The objectives of this study were to identify meta-QTL mQTL for grain yield GY and anthesis silking interval ASI across 18 bi-parental maize populations evaluated in the same conditions across managed water stressed and well watered environments. Mean phenotypic variance explained by each mQTL varied from 1.
Each physical interval of the mQTL consisted of 5 to candidate genes. This is the first extensive report on meta-analysis of data from over individuals genotyped using the same SNP platform and evaluated in the same conditions across a wide range of managed water-stressed and well-watered environments.
Maize is a staple food in many of the SSA countries and is commonly grown by resource poor, small-scale farmers in rural areas. It covers 25 million hectares in SSA that produce 38 million metric tons [ 1 ] but the average maize yield in the region is estimated at 1.
Given the unpredictable nature of drought and climate Anthesis-to-silking interval over years, breeders must develop improved maize hybrids that are able to withstand drought stress without significant yield penalty under optimal rainfall conditions [ 3 - 5 ]. For developing drought tolerant maize, selection can be done directly under water stress, indirectly under well-watered optimal conditions, or under both optimal and stress conditions [ 6 ].
However, heritability of grain yield under water stress has been reported to be lower than yield under optimal environments [ 7 ]. Hence, physiologists and breeders have devoted significant efforts in identifying relevant secondary traits correlated to grain yield for indirect selection.
These include anthesis silking interval ASI between male and female flowering and several other morpho-physiological traits [ 89 ]. The ability to transfer target genomic regions associated with trait s of interest using molecular markers resulted in extensive QTL mapping experiments in most economically important crops.
Using MABC, Ribaut and Ragot [ 4 ] introgressed 5 QTL associated with yield components and flowering in maize from a donor parent into a drought susceptible recurrent parent. The authors reported increased grain yield and reduced ASI under water-limited conditions. The best MABC progeny outperformed the recurrent parent by two to four times under severe drought conditions, with no yield reduction under optimal conditions.
However, drought is a complex trait influenced by genetic background and other environmental factors; thus, relying on a few QTL for MABC is unlikely to create optimally drought tolerant lines for target population of environments.
Individual drought associated QTL generally explain a very small proportion of the phenotypic variance for grain yield, ASI or barrenness. QTL for drought related traits are also often cross-specific and remain undetected in crosses from different genetic backgrounds.
Most QTL are detected under either drought stress or optimal conditions not bothand there is no assurance that QTL detected from inbred lines will function in the same manner in hybrids.
Thus, they must be fully validated in several environmental conditions and hybrid combinations before deployment in a large breeding program. MARS is another marker based breeding technology that seeks to accumulate favorable alleles from several genomic regions within a single population [ 11 ].
In maize, the MARS protocol involves a development and evaluation of testcross performance of bi-parental populations in multi-location experiments; b genotyping of the F2: All these populations have been phenotyped with common protocols and genotyped under a common single nucleotide polymorphism SNP platform.
Co-localized QTL may not be identical, however, especially when they are associated with large confidence intervals.Anthesis — silk interval: An indicator of stress One of the best indicators of how plants respond to stress during flowering is the Anthesis — Silk Interval, ASI.
This measures the time in days between pollen shed and silk emergence. at CIMMYT have demonstrated that a short Anthesis to Silking Interval (ASI) is an important component of drought tolerance in maize.
In this study, one hundred and thirty five F. Experiments conducted by CIMMYT demonstrated that maize varieties such as Katumani composite escape drought and have a long anthesis to silking interval (ASI).
ASI which is defined as the duration between male and female flowering in maize, has been used .
anthesis silking interval Term Accession: TO Aspect: plant_trait_ontology Synonyms (3) ANTSKIT, ASI, FLWSLKINTER Definition: A difference of the average number of days between the maize tassel flowering and the first visible silk (stigma) on the maize ear.
Comment. The Anthesis to Silking Interval (ASI) is highly correlated to grain yields under drought stress as shown by experiments conducted at CIMMYT, Mexico.
This study aimed at combining both earliness and short ASI in one maize genotype. Early-maturing, open pollinated varieties (OPVs) . Anthesis-to-silking interval (ASI) was obtained by subtracting the Julian date of first visible anther from the Julian date of first visible stigma.
Two effects of the introgressed segment were estimated: initial growth rate (HW6) mid-season growth rate (HGR).