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We evaluated root system architecture (RSA) of a set of 58 historical spring wheat cultivars from Pakistan representing 105 years of selection breeding. The evaluations were carried out under control and water-limited conditions using a high-throughput phenotyping system coupled with RhizoVision Explorer software. The cultivars were classified into three groups based on release year as cultivars released pre-1965, released between 1965 and 2000, and cultivars released post-2000. Under water-limited conditions a decline in 20 out of 25 RSA component traits was observed in pre-1965 cultivars group. Whereas cultivars released after the 1965, so-called green revolution period, showed a decline in 17 traits with significant increments in root length, depth, and steep angle frequency which are important root traits for resource-uptake under water-limited conditions. Similarly, cultivars released after 2000 indicated an increase in the number of roots, depth, diameter, surface area, and steep angle frequency. The coefficient of correlation analysis showed a positive correlation between root depth and yield-related traits under water-limited conditions. We also investigated the effects of green-revolution genes (Rht1) and some phenology-related genes such as DRO1, TaMOR, TaLTPs, TaSus-2B on RSA and identified significant associations of these genes with important root traits. There was strong selection pressure on DRO1 gene in cultivated wheat indicating the allele fixed in modern wheat cultivars is different from landraces. The expression of DRO1, and TaMOR were retrieved from an RNAseq experiment, and results were validated using qRT-PCR. The highest expression of DRO1 and TaMOR was found in Chakwal-50, a rainfed cultivar released in 2008, and MaxiPak-65 released in 1965. We conclude that there is a positive historic change in RSA after 1965 that might be attributed to genetic factors associated with favored RSA traits. Furthermore, we suggest root depth and steep angle as promising traits to withstand water-limited environments and may have implications in selection for breeding. [ABSTRACT FROM AUTHOR]

It is important to understand the genetic gain achieved through selection of key yield traits for planning future breeding strategies in developing high yielding wheat (Triticum aestivum L.) cultivars. The aim of this study was to characterize the genetic changes and genotype × environment (G×E) interaction by additive main effect and multiplicative interactions (AMMI) for morphological, physiological, and yield component traits under five environments using 24 wheat cultivars released from 1911 to 2016 in Pakistan. There was a significant increase in grain yield (9.03 kg ha−1 yr−1, 0.37%), and plant height was reduced linearly (−0.26 cm yr−1, −0.33%). The traits waxiness, leaf rolling, harvest index, spike length, and grains per spike significantly increased but the gain was only 0.16–0.2% per year. Analysis of variance revealed that genotype, environment, and G×E interaction were highly significant (P <.01) for all traits except relative chlorophyll content, biomass, days to maturity, and number of spikes. Gene‐specific markers identified the durable resistance gene Lr67/Yr46/Sr55/Pm46 in obsolete cultivars as early as 1911, whereas the photoperiod‐insensitive allele Ppd‐D1a and reduced height alleles Rht‐B1b and Rht‐D1b were present only in the post‐1965 cultivars. Diversity analysis based on a 50K single nucleotide polymorphism genotyping array clearly differentiated temporal patterns in 24 cultivars, which was correlated with the agronomic performance of the cultivars. This dataset provided detailed insight into the performance of historical wheat cultivars and could help in devising wheat breeding strategies to focus on the traits contributing to grain yield and have slower rate of genetic progress. Core Ideas: The genetic gain in morphology of Pakistani bread wheat cultivars over 105 yr areas was assessed.Leaf rolling, waxiness, and grains/spikes associated with genetic gains in grain yield were achieved by breeding.The performance and stability of yield and yield‐related traits was analyzed for the different cultivars. [ABSTRACT FROM AUTHOR]

Key message: Genetic diversity, population structure, LD decay, and selective sweeps in 687 wheat accessions were analyzed, providing relevant guidelines to facilitate the use of the germplasm in wheat breeding. Common wheat (Triticum aestivum L.) is one of the most widely grown crops in the world. Landraces were subjected to strong human-mediated selection in developing high-yielding, good quality, and widely adapted cultivars. To investigate the genome-wide patterns of allelic variation, population structure and patterns of selective sweeps during modern wheat breeding, we tested 687 wheat accessions, including landraces (148) and cultivars (539) mainly from China and Pakistan in a wheat 90 K single nucleotide polymorphism array. Population structure analysis revealed that cultivars and landraces from China and Pakistan comprised three relatively independent genetic clusters. Cultivars displayed lower nucleotide diversity and a wider average LD decay across whole genome, indicating allelic erosion and a diversity bottleneck due to the modern breeding. Analysis of genetic differentiation between landraces and cultivars from China and Pakistan identified allelic variants subjected to selection during modern breeding. In total, 477 unique genome regions showed signatures of selection, where 109 were identified in both China and Pakistan germplasm. The majority of genomic regions were located in the B genome (225), followed by the A genome (175), and only 77 regions were located in the D genome. EigenGWAS was further used to identify key selection loci in modern wheat cultivars from China and Pakistan by comparing with global winter wheat and spring wheat diversity panels, respectively. A few known functional genes or loci found within these genome regions corresponded to known phenotypes for disease resistance, vernalization, quality, adaptability and yield-related traits. This study uncovered molecular footprints of modern wheat breeding and explained the genetic basis of polygenic adaptation in wheat. The results will be useful for understanding targets of modern wheat breeding, and in devising future breeding strategies to target beneficial alleles currently not pursued. [ABSTRACT FROM AUTHOR]

We investigated alleles at 31 loci associated with adaptability, yield, and end-use quality in 107 wheat (Triticum aestivum L.) landraces (WLRs) and 121 improved historical wheat cultivars (HWCs) from Pakistan. The WLRs were categorized into two further subgroups: 36 pre-Green-Revolution landraces released as cultivars and 71 geographically spread landraces from all over Pakistan. Alleles VrnA1a, TaGW2-6A-A, TaCKX6-D1b, Pinb-D1b, Psy-A1b, and Wx-D1b were absent in WLRs, whereas ample diversity was observed at all other loci. In HWCs, only Wx-D1b and Glu-A3e were absent among the alleles tested, whereas the alleles Ppd-D1a (90%), Rht-B1b or Rht-D1b (83.4%), TaCwi-A1a (95%), TaGW2-6A-G (76%), TaCKX6-D1a (77.3%), Glu-A1b (66.1%), Glu-D1d (61.3%), Pina-D1b (88.2%), Pinb-D1a (90%), Psy-A1a (66.1%), Psy-B1b (81.8%), Psy-D1a (86.5%), Ppo-A1a (70%), TaZds-D1b (73.9%), TaLox-B1b (80.1%), and Wx-D1a (100%) predominated, indicating significant improvement in adaptability, yield potential, and end-use quality and unconscious selection for favored alleles. Higher frequencies of favored alleles at the TaCwi-A1 and TaCKX6-D1 loci influencing 1000-kernel weight (TKW) in HWCs indicated that selection pressure on these alleles during breeding successfully contributed to cultivar improvement. Wright's pairwise fixation index (Fst) statistics indicated greater genetic divergence between HWC and WLR collections (0.16) than HWC and WLR cultivars (0.14). Population structure based on functional markers (FMs) using principal component analysis partitioned the germplasm into two distinct groups. High genetic divergence and low admixture between HWCs and WLRs indicated limited use of landraces in wheat breeding in Pakistan. Our results suggested these collections as rich reservoirs of alleles and haplotype combinations that may be useful in future breeding programs. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.), being a staple food crop, is an important nutritional source providing protein and minerals. It is important to fortify staple cereals such as wheat with essential minerals to overcome the problems associated with malnutrition. The experiment was designed to evaluate the status of 11 micronutrients including grain iron (GFe) and zinc (GZn) in 62 wheat cultivars released between 1911 and 2016 in Pakistan. Field trials were conducted over two years and GFe and GZn were quantified by both inductively coupled plasma optical emission spectroscopy (ICP-OES) and energy-dispersive X-ray fluorescence spectrophotometer (EDXRF). The GZn ranged from 18.4 to 40.8 mg/kg by ED-XRF and 23.7 to 38.8 mg/kg by ICP-OES. Similarly, GFe ranged from 24.8 to 44.1 mg/kg by ICP-OES and 26.8 to 36.6 mg/kg by EDEXR. The coefficient of correlation was higher for GZn (r = 0.90), compared to GFe (r = 0.68). Modern cultivars such as Zincol-16 and AAS-2011 showed higher GFe and GZn along with improved yield components. Old wheat cultivars WL-711, C-518 and Pothowar-70, released before 1970, also exhibited higher values of GFe and GZn; however, their agronomic performance was poor. Multivariate analysis using eleven micronutrients (Fe, Zn, Al, Ca, Cu, K, Mg, Mn, Na, Se and P) along with agronomic traits, and genome-wide SNP markers identified the potential cultivar with improved yield, biofortification and wider genetic diversity. Genetic gain analysis identified a significant increase in grain yield (0.4% year−1), while there was negative gain for GFe (−0.11% year−1) and GZn (−0.15% year−1) over the span of 100 years. The Green Revolution Rht-B1 and Rht-D1 genes had a strong association with plant height and grain yield (GY), while semi-dwarfing alleles had a negative effect on GFe and GZn contents. This study provided a valuable insight into the biofortification status of wheat cultivars deployed historically in Pakistan and is a valuable source to initiate a breeding strategy for simultaneous improvement in wheat phenology and biofortification. [ABSTRACT FROM AUTHOR]

A high grain zinc wheat cultivar, Zincol-2016, was released in Pakistan to mitigate mineral malnutrition. Here, we used RNAseq based approach to reveal transcriptional landscape of its developing grains, and to identify genetic variants in zinc (Zn) and iron (Fe) homeostasis genes. Differential gene expression analysis identified 8370 differentially expressed genes (DEGs) over the course of grain filling. The profiling of 265 Fe/Zn homeostasis genes revealed the homeologs of TaNAS9 , TaFER1, TaNAAT2 , TaDMAS, TaZIFL5-A , TaZIFL5-D , TaZIP14-B , TaNRAMP3 , TaVIT1, TaPRI2-D , TabZIPF1-7B , TabZIPF1-7D , TabZIPF2-5A , and TabZIPF2-5B had increased expression in Zincol-2016 relative to other cultivars from expVIP database. The variant calling identified 358 SNPs and 34 InDels in the Fe/Zn homeostasis genes. Two of those SNPs in TaZIP14-B (TraesCS3B02G140400), and TaNAAT2-B (TraesCS1B02G300600), were associated with grain zinc and iron concentrations (GZnC and GFeC) in a diverse panel of 145 wheat cultivars. The Zincol-type alleles of both genes significantly increased GZnC and GFeC by 7.3–8.6% and 5.9–6.3%, respectively. In addition, 8 SNPs causing missense mutation and 2 InDels causing frameshift mutation were found unique to Zincol. The present study forms a basis for understanding the genetic basis of high GZnC and GFeC in Zincol-2016 and can help efforts to biofortify other wheat varieties. [Display omitted] • RNAseq of Zincol-2016 developing grains during grain filling stage was conducted. • Increased expression of several Fe/Zn homeostasis genes was observed in Zincol. • In total 358 SNPs and 34 InDels in known Fe/Zn homeostasis genes were identified. • Comparison with variants data of other wheat cultivars identified 10 unique variants in the Fe/Zn homeostasis genes of Zincol. • Zincol-type alleles of TaZIP14-B and TaNAAT2-B increased grain iron and zinc contents. [ABSTRACT FROM AUTHOR]

Characterization of genomic regions underlying adaptation of landraces can reveal a quantitative genetics framework for local wheat (Triticum aestivum L.) adaptability. A collection of 512 wheat landraces from the eastern edge of the Fertile Crescent in Iran and Pakistan were genotyped using genome-wide single nucleotide polymorphism markers generated by genotyping-by-sequencing. The minor allele frequency (MAF) and the heterozygosity (H) of Pakistani wheat landraces (MAF = 0.19, H = 0.008) were slightly higher than the Iranian wheat landraces (MAF = 0.17, H = 0.005), indicating that Pakistani landraces were slightly more genetically diverse. Population structure analysis clearly separated the Pakistani landraces from Iranian landraces, which indicates two separate adaptability trajectories. The large-scale agro-climatic data of seven variables were quite dissimilar between Iran and Pakistan as revealed by the correlation coefficients. Genome-wide association study identified 91 and 58 loci using agroclimatic data, which likely underpin local adaptability of the wheat landraces from Iran and Pakistan, respectively. Selective sweep analysis identified significant hits on chromosomes 4A, 4B, 6B, 7B, 2D, and 6D, which were colocalized with the loci associated with local adaptability and with some known genes related to flowering time and grain size. This study provides insight into the genetic diversity with emphasis on the genetic architecture of loci involved in adaptation to local environments, which has breeding implications., (© 2021 The Authors. The Plant Genome published by Wiley Periodicals LLC on behalf of Crop Science Society of America.)