Genomic associations for drought tolerance on the short arm of wheat chromosome 4B

Abstract

Drought is a major constraint to maintaining yield stability of wheat in rain fed and limited irrigation agro-ecosystems. Genetic improvement for drought tolerance in wheat has been difficult due to quantitative nature of the trait involving multiple genes with variable effects and lack of effective selection strategies employing molecular markers. Here, a framework molecular linkage map was constructed using 173 DNA markers randomly distributed over the 21 wheat chromosomes. Grain yield and other drought-responsive shoot and root traits were phenotyped for 2 years under drought stress and well-watered conditions on a mapping population of recombinant inbred lines (RILs) derived from a cross between drought-sensitive semidwarf variety "WL711" and drought-tolerant traditional variety "C306". Thirty-seven genomics region were identified for 10 drought-related traits at 18 different chromosomal locations but most of these showed small inconsistent effects. A consistent genomic region associated with drought susceptibility index (qDSI.4B.1) was mapped on the short arm of chromosome 4B, which also controlled grain yield per plant, harvest index, and root biomass under drought. Transcriptome profiling of the parents and two RIL bulks with extreme phenotypes revealed five genes underlying this genomic region that were differentially expressed between the parents as well as the two RIL bulks, suggesting that they are likely candidates for drought tolerance. Syntenic genomic regions of barley, rice, sorghum, and maize genomes were identified that also harbor genes for drought tolerance. Markers tightly linked to this genomic region in combination with other important regions on group 7 chromosomes may be used in marker-assisted breeding for drought tolerance in wheat.

QTL Analysis for Drought Tolerance in Wheat: Present Status and Future Possibilities

“…However, MABC has only been rarely attempted for the improvement of drought tolerance in wheat on a large scale. For example, under the Generation Challenge Programme funded by CIMMYT, Mexico, and the National Initiative on Climate Resilient Agriculture Project supported by ICAR, India, efforts were made to introgress QTLs for several drought-related traits (canopy temperature, chlorophyll content, stay green habit, NDVI values, days to anthesis, grain yield, and its related traits) into two elite Indian wheat cultivars (HD2733 and GW322) through MABC [78] (for details of QTLs, see Kirigwi et al [46], Pinto et al [24], Kumar et al [53], and Kadam et al [69]). After foreground and background selection (90% recurrent parent), the BC 1 F 2 -and BC 2 F 2 -containing QTLs for drought-related traits and the 90% genome of the recurrent parent genotypes were advanced for seed multiplication.…”

Drought Resistance in Crops: Physiological and Genetic Basis of Traits for Crop Productivity

“…QTLs for root traits have been reported on chromosomes 1B, 2A, 3B, 3D, 4A, 4B, 5D, 6A and 6B explaining up to 24.3 % of PV in wheat (Bai et al 2013;Liu et al 2013, Table 11.1). QTLs on 4BS explaining up to 14.5 % of PV have been identified in WL711/C306 RIL population for root traits and co-located with GY under drought stress during post-anthesis stage (Kadam et al 2012). Total of 9 QTLs for four root traits namely maximum root length, root biomass above 30 cm length, root biomass below 30 cm length and root: shoot ratio have been reported under irrigated and water stress condition.…”

Root trait characteristics and genotypic response in wheat under different water regimes

“…The presence of strong GE interaction for these moisture stress adaptive traits signifies the importance of a separate breeding programme for drought tolerance. Recently, Kadam et al (2012) identified that drought-responsive shoot and root traits colocalize on same genomic regions. Chromosome 4B in wheat harbors QTLs for grain yield under drought, harvest index and root biomass, lateral root length, total root length and root tip number for seminal roots at seedling stage (Ren et al 2011;Kadam et al 2012).…”

“…Recently, Kadam et al (2012) identified that drought-responsive shoot and root traits colocalize on same genomic regions. Chromosome 4B in wheat harbors QTLs for grain yield under drought, harvest index and root biomass, lateral root length, total root length and root tip number for seminal roots at seedling stage (Ren et al 2011;Kadam et al 2012). Consistent genomic region associations for shoot and root traits for drought response will further improve the breeding efficiency.…”

“…Ehdaie et al (2012) observed the phenotypic plasticity response of root system on grain yields in wheat and its translocation lines under drought conditions and found positive correlations between root system components and grain yields. Genomic associations with quantitative trait loci for better root systems for higher productivity and water use efficiency have recently been reported in wheat (Sharma et al 2011;Kadam et al 2012).…”