Publications by authors named "Sajid Shokat"

5 Publications

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A GWAS to identify the cereal cyst nematode (Heterodera filipjevi) resistance loci in diverse wheat prebreeding lines.

J Appl Genet 2021 Feb 6;62(1):93-98. Epub 2021 Jan 6.

Geneshifters, 222 Mary Jena Lane, Pullman, WA, 99163, USA.

Yield losses because of cereal cyst nematodes could be as high as 92%, causing a bottleneck for wheat production. An integrated approach (application of pesticides, crop rotation, and use of host resistance) is needed to manage this devastating pathogen where resistant cultivars are considered most effective. This necessitates the identification of nematode-resistant sources in the available germplasm. Here, we report on the genetic mapping of nematode resistance in 255 diverse prebreeding lines (PBLs) employing an association mapping strategy. Altogether, seven additive quantitative trait loci (QTL) were identified on chromosomes 1A, 2A, 2B, 2D, 3A, 6B, and 6D explaining a maximum of 9.42% phenotypic variation where at least five QTL (on chromosomes 2A, 2B, 2D, 6B, and 6D) are located on the same chromosomes that harbor the already known nematode resistance genes. Resistant PBLs carried Aegilops squarrosa (436) in their pedigree which could be the possible source of positive alleles. To add to it, better yield performance of the identified nematode-resistant lines under stress conditions indicates that the germplasm can provide both nematode resistance and high-yielding cultivars.
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http://dx.doi.org/10.1007/s13353-020-00607-yDOI Listing
February 2021

Activities of leaf and spike carbohydrate-metabolic and antioxidant enzymes are linked with yield performance in three spring wheat genotypes grown under well-watered and drought conditions.

BMC Plant Biol 2020 Aug 31;20(1):400. Epub 2020 Aug 31.

Crop Science, Department of Plant and Environmental Sciences, University of Copenhagen, Højbakkegård Allé 13, 2630, Taastrup, Denmark.

Background: To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L (advanced line), L (Vorobey) and L (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while well-watered control plants were kept at 95% pot water holding capacity.

Results: Compared to genotype L and L, pronounced decrease in grain number (NGS), grain yield (GY) and harvest index (HI) were found in genotype L, mainly due to its greater kernel abortion (KA) under drought. A significant positive correlation of leaf monodehydroascorbate reductase (MDHAR) with both NGS and HI was observed. In contrast, significant negative correlations of glutathione S-transferase (GST) and vacuolar invertase (vacInv) both within source and sink were found with NGS and HI. Likewise, a significant negative correlation of leaf abscisic acid (ABA) with NGS was noticed. Moreover, leaf aldolase and cell wall peroxidase (cwPOX) activities were significantly and positively associated with thousand kernel weight (TKW).

Conclusion: Distinct physiological markers correlating with yield traits and higher activity of leaf aldolase and cwPOX may be chosen as predictive biomarkers for higher TKW. Also, higher activity of MDHAR within the leaf can be selected as a predictive biomarker for higher NGS in wheat under drought. Whereas, lower activity of vacInv and GST both within leaf and spike can be selected as biomarkers for higher NGS and HI. The results highlighted the role of antioxidant and carbohydrate-metabolic enzymes in the modulation of source-sink balance in wheat crops, which could be used as bio-signatures for breeding and selection of drought-resilient wheat genotypes for a future drier climate.
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http://dx.doi.org/10.1186/s12870-020-02581-3DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7457523PMC
August 2020

Molecular Markers Associated with Agro-Physiological Traits under Terminal Drought Conditions in Bread Wheat.

Int J Mol Sci 2020 Apr 30;21(9). Epub 2020 Apr 30.

International Maize and Wheat Improvement Centre (CIMMYT) km, 45, Carretera Mex-Veracruz, El-Batan, Texcoco CP 56237, Mexico.

Terminal drought stress poses a big challenge to sustain wheat grain production in rain-fed environments. This study aimed to utilize the genetically diverse pre-breeding lines for identification of genomic regions associated with agro-physiological traits at terminal stage drought stress in wheat. A total of 339 pre-breeding lines panel derived from three-way crosses of 'exotics × elite × elite' lines were evaluated in field conditions at Obregon, Mexico for two years under well irrigated as well as drought stress environments. Drought stress was imposed at flowering by skipping the irrigations at pre and post anthesis stage. Results revealed that drought significantly reduced grain yield (Y), spike length (SL), number of grains spikes (NGS) and thousand kernel weight (TKW), while kernel abortion (KA) was increased. Population structure analysis in this panel uncovered three sub-populations. Genome wide linkage disequilibrium (LD) decay was observed at 2.5 centimorgan (cM). The haplotypes-based genome wide association study (GWAS) identified significant associations of Y, SL, and TKW on three chromosomes; 4A (HB10.7), 2D (HB6.10) and 3B (HB8.12), respectively. Likewise, associations on chromosomes 6B (HB17.1) and 3A (HB7.11) were found for NGS while on chromosome 3A (HB7.12) for KA. The genomic analysis information generated in the study can be efficiently utilized to improve Y and/or related parameters under terminal stage drought stress through marker-assisted breeding.
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http://dx.doi.org/10.3390/ijms21093156DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7247584PMC
April 2020

Mapping of QTLs Associated with Yield and Yield Related Traits in Durum Wheat ( Desf.) Under Irrigated and Drought Conditions.

Int J Mol Sci 2020 Mar 30;21(7). Epub 2020 Mar 30.

Leibniz Institute of Plant Genetics and Crop Plant Research, Corrensstr. 3, Seeland OT, 06466 Gatersleben, Germany.

Global durum wheat consumption ( Desf.) is ahead of its production. One reason for this is abiotic stress, e.g., drought. Breeding for resistance to drought is complicated by the lack of fast, reproducible screening techniques and the inability to routinely create defined and repeatable water stress conditions. Here, we report the first analysis of dissection of yield and yield-related traits in durum wheat in Pakistan, seeking to elucidate the genetic components of yield and agronomic traits. Analysis of several traits revealed a total of 221 (160 with logarithm of odds (LOD) > 2 ≤ 3 and 61 with LOD > 3) quantitative trait loci (QTLs) distributed on all fourteen durum wheat chromosomes, of which 109 (78 with LOD > 2 ≤ 3 and 31 with LOD > 3) were observed in 2016-17 (S1) and 112 (82 with LOD > 2 ≤ 3 and 30 with LOD > 3) were observed in 2017-18 (S2). Allelic profiles of yield QTLs on chromosome 2A and 7B indicate that allele A of and allele B of can enhance the Yd up to 6.16% in control and 5.27% under drought. Moreover, if combined, a yield gain of up to 11% would be possible.
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http://dx.doi.org/10.3390/ijms21072372DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7177892PMC
March 2020

Harnessing genetic potential of wheat germplasm banks through impact-oriented-prebreeding for future food and nutritional security.

Sci Rep 2018 08 21;8(1):12527. Epub 2018 Aug 21.

ICAR-Indian Agricultural Research Institute, Regional Station, Shimla, 171004, India.

The value of exotic wheat genetic resources for accelerating grain yield gains is largely unproven and unrealized. We used next-generation sequencing, together with multi-environment phenotyping, to study the contribution of exotic genomes to 984 three-way-cross-derived (exotic/elite1//elite2) pre-breeding lines (PBLs). Genomic characterization of these lines with haplotype map-based and SNP marker approaches revealed exotic specific imprints of 16.1 to 25.1%, which compares to theoretical expectation of 25%. A rare and favorable haplotype (GT) with 0.4% frequency in gene bank identified on chromosome 6D minimized grain yield (GY) loss under heat stress without GY penalty under irrigated conditions. More specifically, the 'T' allele of the haplotype GT originated in Aegilops tauschii and was absent in all elite lines used in study. In silico analysis of the SNP showed hits with a candidate gene coding for isoflavone reductase IRL-like protein in Ae. tauschii. Rare haplotypes were also identified on chromosomes 1A, 6A and 2B effective against abiotic/biotic stresses. Results demonstrate positive contributions of exotic germplasm to PBLs derived from crosses of exotics with CIMMYT's best elite lines. This is a major impact-oriented pre-breeding effort at CIMMYT, resulting in large-scale development of PBLs for deployment in breeding programs addressing food security under climate change scenarios.
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http://dx.doi.org/10.1038/s41598-018-30667-4DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6104032PMC
August 2018