Hexaploid Wheat Genotypes Research Articles

Do Different Wheat Ploidy Levels Respond Differently Against Stripe Rust Infection: Interplay between Reactive Oxygen Species (ROS) and the Antioxidant Defense System?

Wheat stripe rust (Puccinia striiformis f. sp. tritici, Pst) is the most damaging wheat disease, causing substantial losses in global wheat production and productivity. Our study aimed to unravel the complex reciprocity between reactive oxygen species and the antioxidant defense system as a source of resistance against stripe rust in diploid, tetraploid and hexaploid wheat genotypes. The significant genetic variability for stripe rust in the materials under study was evident as the genotypes showed contrasting responses during both the adult and seedling stages. Our thorough perspective on the biochemical responses of wheat genotypes to stripe rust infection revealed distinct patterns in oxidative damage, antioxidant enzymes and photosynthetic pigments. Principal component analysis revealed inverse correlations between antioxidants and ROS, underscoring their key function in maintaining the cellular redox balance and protecting plants against oxidative damage. Diploid (Ae. tauschii) wild wheat exhibited a better biochemical defense system and greater resistance to stripe rust than the tetraploid (T. durum) and hexaploid (Triticum aestivum) wheat genotypes. The antioxidant enzyme activity of durum wheat was moderate compared to diploid and hexaploid wheat genotypes. The hexaploid wheat genotypes exhibited increased ROS production, reduced antioxidant enzyme activity and decreased photosynthetic pigment levels. This study enhances understanding of the antioxidant defense system across different wheat ploidies facing stripe rust, serving as a valuable strategy for improving crop disease resistance. This study validated the biochemical response of stripe rust-resistant and susceptible candidate genotypes, which will be used to develop genetic resources for discovering stripe rust resistance genes in wheat.

Mapping and characterization of rust resistance genes Lr53 and Yr35 introgressed from Aegilops species

Key messageThe rust resistance genes Lr53 and Yr35 were introgressed into bread wheat from Aegilops longissima or Aegilops sharonensis or their S-genome containing species and mapped to the telomeric region of chromosome arm 6BS.Wheat leaf and stripe rusts are damaging fungal diseases of wheat worldwide. Breeding for resistance is a sustainable approach to control these two foliar diseases. In this study, we used SNP analysis, sequence comparisons, and cytogenetic assays to determine that the chromosomal segment carrying Lr53 and Yr35 was originated from Ae.longissima or Ae. sharonensis or their derived species. In seedling tests, Lr53 conferred strong resistance against all five Chinese Pt races tested, and Yr35 showed effectiveness against Pst race CYR34 but susceptibility to race CYR32. Using a large population (3892 recombinant gametes) derived from plants homozygous for the ph1b mutation obtained from the cross 98M71 × CSph1b, both Lr53 and Yr35 were successfully mapped to a 6.03-Mb telomeric region of chromosome arm 6BS in the Chinese Spring reference genome v1.1. Co-segregation between Lr53 and Yr35 was observed within this large mapping population. Within the candidate region, several nucleotide-binding leucine-rich repeat genes and protein kinases were identified as candidate genes. Marker pku6B3127 was completely linked to both genes and accurately predicted the absence or presence of alien segment harboring Lr53 and Yr35 in 87 tetraploid and 149 hexaploid wheat genotypes tested. We developed a line with a smaller alien segment (< 6.03 Mb) to reduce any potential linkage drag and demonstrated that it conferred resistance levels similar to those of the original donor parent 98M71. The newly developed introgression line and closely linked PCR markers will accelerate the deployment of Lr53 and Yr35 in wheat breeding programs.

Evaluation of wheat genotypes for resistance to bacterial leaf streak caused by Xanthomonas translucens pv. undulosa in field and greenhouse trials

Bacterial leaf streak (BLS), caused by Xanthomonas translucens pv. undulosa, is a devastating cereal disease that is becoming more common in Iran. A cost-effective and realistic strategy to cope with BLS is planting of BLS-resistant cultivars. To discover BLS-resistant genotypes, 360 hexaploid wheat genotypes were selected and inoculated with a local strain of Xanthomonas translucens pv. undulosa in the field and greenhouse in two years (2019 & 2020). In the field experiments, disease reaction of wheat plants was assessed based on both percentage of disease incidence (PDI) and the percentage of disease severity (PDS). In the greenhouse experiment, disease reaction was evaluated as the disease severity (DS). The genotypes with PDS, PDI, and DS values ≤ 20% were considered BLS-resistant or semi-resistant. Genotypes with zero or very low PDS, PDI and DS during the first and second years were considered highly resistant to the disease. Despite resistant genotypes being more prevalent than susceptible genotypes in each year, genotype responses to BLS varied over the two years, but in both years, most genotypes showed a resistance response. Forty-six genotypes (12.8%) were consistently BLS-resistant across years in the field and greenhouse trials. In 2020, field BLS intensity ratings (PDI and PDS) were positively correlated with flag leaf width and days to maturity. In contrast, PDI and PDS were negatively correlated with plant height, peduncle length, and spike length. In 2019, no significant correlations were found between PDI, PDS, and phenotypic traits. Cluster heatmaps and principal component analysis (PCA) separated resistant and susceptible genotypes. In BLS-resistant genotypes, plant height, peduncle length, and spike length were significantly longer, but flag leaf width and days to maturity were shorter. This study identified new and diverse sources of resistance to BLS that could be used in wheat breeding efforts.

Assessment of intra- and inter-genetic diversity in tetraploid and hexaploid wheat genotypes based on omega, gamma and alpha-gliadin profiles.

Durum and bread wheat are well adapted to the Mediterranean Basin. Twenty-three genotypes of each species were grown to evaluate the intra- and inter-genetic diversity based on omega (ω), gamma (γ) and alpha (α)-gliadin profiles. To achieve this purpose, the endosperm storage proteins (both gliadins and glutenins) were extracted from wheat grains and electrophoresed on sodium dodecyl sulfate (SDS)-polyacrylamide gels. The results of SDS-Polyacrylamide Gel Electrophoresis (SDS-PAGE) revealed nine polymorphic loci out of 16 loci with durum wheat genotypes and nine polymorphic loci out of 18 loci with bead wheat genotypes. The polymorphisms revealed by the SDS-PAGE were 56% and 50% in durum and bread wheat genotypes, respectively. Using the cluster analysis, the durum wheat genotypes were clustered into five groups, while the bread wheat genotypes were grouped into six clusters using un-weighed pair group mean analyses based on ω, γ, and α-gliadins profiles. The 46 durum and bread wheat genotypes were grouped into seven clusters based on the combined ω, γ, and α-gliadins profiles revealed by the SDS-PAGE. The in silico analysis determined the intra-genetic diversity between bread and durum wheat based on the sequences of ω, γ, and α-gliadins. The alignment of ω-gliadin revealed the highest polymorphism (52.1%) between bread and durum wheat, meanwhile, the alignment of γ and α-gliadins revealed very low polymorphism 6.6% and 15.4%, respectively. According to computational studies, all gliadins contain a lot of glutamine and proline residues. The analysis revealed that the bread wheat possessed ω and γ -gliadins with a lower content of proline and a higher content of glutamine than durum wheat. In contrast, durum wheat possessed α-gliadin with a lower content of proline and a higher content of glutamine than bread wheat. In conclusion, the SDS-PAGE, in silico and computational analyses are effective tools to determine the intra- and inter-genetic diversity in tetraploid and hexaploid wheat genotypes based on ω, γ, and α-gliadins profiles.

Assessment of genetic variation among wheat genotypes for drought tolerance utilizing microsatellite markers and morpho-physiological characteristics

Drought is a major abiotic stress that severely limits sustainable wheat (Triticum aestivum L.) productivity via morphological and physio-biochemical alterations of cellular processes. The complex nature and polygenic control of drought tolerance traits make breeding tolerant genotypes quite challenging. However, naturally occurring variabilities among wheat germplasm resources could potentially help combating drought. The present study was conducted to assess the drought tolerance of 18 Bangladeshi hexaploid wheat genotypes, focusing on the identification of potent sources of diversity by combining microsatellite markers, also known as single sequence repeat markers, and morpho-physiological characteristics that might help accelerating wheat crop improvement programs. Initially, the genotypes were evaluated using 25 microsatellite markers followed by an on-field evaluation of 7 morphological traits (plant height, spike number, spike length, grains per spike, 1000-grain weight, grain yield, biological yield) and 6 physiological traits (SPAD value, membrane stability index, leaf relative water content, proline content, canopy temperature depression, and leaf K+ ion content). The field-trial was conducted in a factorial fashion of 18 wheat genotypes and two water regimes (control and drought) following a split-plot randomized complete block design. Regardless of genotype, drought was significantly damaging for all the tested traits; however, substantial variability in drought stress tolerance was evident among the genotypes. Spike length, 1000-grain weight, SPAD value, leaf relative water content, canopy temperature depression, proline content, and potassium (K+) ion content were the most representative of drought-induced growth and yield impairments and also correlated well with the contrasting ability of genotypic tolerance. Microsatellite markers amplified 244 alleles exhibiting 79% genetic diversity. Out of 25 markers, 23 was highly polymorphic showing 77% average polymorphism. Morpho-physiological trait-based hierarchical clustering and microsatellite marker-based neighbor-jointing clustering both revealed three genotypic clusters with 71% co-linearity between them. In both cases, the genotypes Kanchan, BAW-1147, BINA Gom 1, BARI Gom 22, BARI Gom 26, and BARI Gom 33 were found to be comparatively more tolerant than the other tested genotypes, showing potential for cultivation in water-deficit environments. The findings of this study would contribute to the present understanding of drought tolerance in wheat and would provide a basis for future genotype selection for drought-tolerant wheat breeding programs.

Physio-Chemical and Agronomic-Based Characterization of Synthetic Hexaploid Wheat Germplasm under Field Imposed Conditions of Drought and Heat Stress

Abiotic stresses, such as a drought and heat, are potential constraints limiting wheat production across the globe. This current perspective study intended to characterize the performance of exotic synthetic hexaploid (SH) wheat genotypes on a physiological, biochemical, and agronomic basis under field-based drought and heat conditions. The tri-replicate experiments were conducted in two seasons using two-factorial arrangements in a randomized complete block design (RCBD) with stresses as one factor and genotypes as another factor. The recorded data were statistically analyzed using computer-based software statistix8.1 and R-studio. In this study, all the physiological parameters (total chlorophyll, stomatal conductance, photosynthesis rate, transpiration rate, and cell membrane stability percentage), biochemical stress markers (antioxidant enzymes, glycine betaine, and proline), and agronomic traits (flag leaf area, plant height, tillers per plant, spike length, grains per spike, and thousand grain weight) varied significantly under separate and combined regimes of drought and heat stresses. All traits varied in same direction, excluding glycine betaine and proline, which varied in the opposite direction because of stress, as explicated by correlation analysis. Furthermore, PCA and heatmap analysis confirmed that the expression of the traits varied more significantly because of combined regimes of drought and heat stresses as compared to controlled and isolated applications. Interestingly, synthetic hexaploid (SH) genotypes depicted similar responses to individual and integrated regimes of drought and heat stresses. The current study proved that deciphering the physiological, biochemical, and agronomic performance of wheat genotypes under stress can provide effective criteria for the future selection of wheat germplasm for breeding against drought and heat stresses.

Amylase Trypsin Inhibitors (ATIs) in a Selection of Ancient and Modern Wheat: Effect of Genotype and Growing Environment on Inhibitory Activities

Wheat amylase-trypsin inhibitors (ATIs) are a family of plant defense proteins with an important role in human health for their involvement in allergies, celiac disease and non-celiac wheat sensitivity. Information about the differences in ATI activities among wheat genotypes and the influence of the growing environment is scarce. Therefore, ten selected wheat accessions with different ploidy level and year of release, previously characterized for their ATI gene sequences, were grown during three consecutive crop years at two growing areas and used for in vitro ATI activities. The contributions of the genotype and the crop year were significant for both activities. The hexaploid wheat genotypes showed the highest inhibitory activities. Einkorn had a peculiar behavior showing the lowest alpha-amylase inhibitory activity, but the highest trypsin inhibitory activity. It was not possible to observe any trend in ATI activities as a function of the release year of the wheat samples. The two inhibitory activities were differently affected by the growing conditions and were negatively correlated with the protein content. This information can be important in understanding the extent of variation of ATI inhibitory properties in relation to the wheat genotype and the growing environment and the impact of ATIs, if any, on human health and nutrition.

Investigation of Yield and Quality Parameters of Some Local and Newly Registered Bread (hexaploid) Wheat (Triticum aestivum L.) Genotypes Under Rainfed Agricultural Conditions

Investigation of Yield and Quality Parameters of Some Local and Newly Registered Bread (hexaploid) Wheat (Triticum aestivum L.) Genotypes Under Rainfed Agricultural Conditions

The wheat dioxygenase BX6 is involved in the formation of benzoxazinoids in planta and contributes to plant defense against insect herbivores

Benzoxazinoids are plant specialized metabolites with defense properties, highly abundant in wheat (Triticum), one of the world’s most important crops. The goal of our study was to characterize dioxygenase BX6 genes in tetraploid and hexaploid wheat genotypes and to elucidate their effects on defense against herbivores. Phylogenetic analysis revealed four BX6 genes in the hexaploid wheat T. aestivum, but only one ortholog was found in the tetraploid (T. turgidum) wild emmer wheat and the cultivated durum wheat. Transcriptome sequencing of durum wheat plants, damaged by either aphids or caterpillars, revealed that several BX genes, including TtBX6, were upregulated upon caterpillar feeding, relative to the undamaged control plants. A virus-induced gene silencing approach was used to reduce the expression of BX6 in T. aestivum plants, which exhibited both reduced transcript levels and reduced accumulation of different benzoxazinoids. To elucidate the effect of BX6 on plant defense, bioassays with different herbivores feeding on BX6-silenced leaves were conducted. The results showed that plants with silenced BX6 were more susceptible to aphids and the two-spotted spider mite than the control. Overall, our study indicates that wheat BX6 is involved in benzoxazinoid formation in planta and contributes to plant resistance against insect herbivores.

The Physiological Basis of Improved Heat Tolerance in Selected Emmer-Derived Hexaploid Wheat Genotypes.

Wheat is sensitive to high-temperature stress with crop development significantly impaired depending on the severity and timing of stress. Various physiological mechanisms have been identified as selection targets for heat tolerance; however, the complex nature of the trait and high genotype × temperature interaction limits the selection process. A three-tiered phenotyping strategy was used to overcome this limitation by using wheat genotypes developed from the ancient domesticated wheat, emmer (Triticum dicoccon Schrank), which was considered to have a wide variation for abiotic stress tolerance. A contrasting pair of emmer-based hexaploid lines (classified as tolerant; G1 and susceptible; G2) developed from a backcross to the same recurrent hexaploid parent was chosen based on heat stress responses in the field and was evaluated under controlled glasshouse conditions. The same pair of contrasting genotypes was also subsequently exposed to a short period of elevated temperature (4 days) at anthesis under field conditions using in-field temperature-controlled chambers. The glasshouse and field-based heat chambers produced comparable results. G1 was consistently better adapted to both extended and short periods of heat stress through slow leaf senescence under heat stress, which extended the grain filling period, increased photosynthetic capacity, increased grain filling rates, and resulted in greater kernel weight and higher yield. The use of a combination of phenotyping methods was effective in identifying heat tolerant materials and the mechanisms involved.

Prevalence of Puroindoline Genes and Their Impact on Quality Traits in A Diverse Germplasm of Wheat Genotypes

Grain hardness is an imperative attribute that determines the end-use quality of wheat. Variation in grain hardness is usually controlled by Puroindoline (pin-a and pin-b) genes located on the 5D chromosome. The study was aimed to reveal different mutations in Puroindoline genes utilizing the STS-marker approach and their association with important quality attributes in 100 hexaploid wheat genotypes (96 from Pakistan and 4 from CIMMYT). Overall, seven puroidoline genes were identified. Among them Pina-d1b(null) (85%) was most common while Pinb-d1i (1%) and Pinb-d1ab (1%) were most rare gene. Out of 100 genotypes, 97 had hard texture either with single or double mutant pin-genes, while three had a soft texture with wild type (Pinad1a/Pinb-d1a) pin-genes. All four quality attributes revealed a vast deviation among germplasm, while their correlation analysis revealed the highest association (r=0.71) between thousand-grain weight and protein content. In addition, three out of four quality traits, i.e. thousandgrain weight, SDS-sedimentation value and protein content, showed the highest mean values for double mutant (Pina-d1b/Pinb-d1b) followed by single mutant, i.e. Pina-d1b. The present study facilitates breeders for varietal selection (hard or soft) according to end-use quality and offers valuable information for improving wheat quality.

Differential reaction of hexaploid and tetraploid wheat to Fusarium graminearum chemotypes in a controlled environment

Fusarium head blight (FHB) has a negative impact on cereal food safety, quality and yield. The majority of FHB resistance genes in wheat (Triticum spp.) have been identified based on reaction to Fusarium graminearum, which, in Canada, has two prevalent trichothecene chemotypes, 3-acetyl-deoxyinvalenol (ADON) and 15-ADON. Three hexaploid (Triticum aestivum L.) and four tetraploid (Triticum turgidum L. ssp. durum and Triticum turgidum L. spp. dicoccoides (Korn. ex Asch. & Graebn.) Thell.) wheat genotypes with different genes for resistance and with different reactions to F. graminearum were evaluated in replicated greenhouse trials to determine if the resistance genes currently deployed in Canadian wheat are effective against both the 3-ADON and 15-ADON chemotypes. The development of FHB was rated as disease severity. The genotypes showed differential responses, with a higher level of disease development in the hexaploid wheat genotypes inoculated with the 3-ADON than with the 15-ADON chemotype. The opposite was observed in the tetraploid wheat genotypes. Tetraploid genotype BGRC3487 and a hexaploid genotype ND2710 showed similar resistance to both 3-ADON and 15-ADON chemotypes. These would be effective sources to breed lines resistant to both 3-ADON and 15-ADON chemotypes and reduce FHB risk.

Evaluation of wheat genotypes for field resistance to wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT) and correlation between yield loss and disease incidence in the Brazilian Cerrado

Wheat blast caused by Magnaporthe oryzae pathotype Triticum (MoT) has become an important fungal disease on wheat and is now present in most of the important wheat-producing tropical regions of the world. This study evaluated head blast incidence on the spikes of 281 hexaploid wheat genotypes and two Triticum durum cultivars across three years (2011–2013) in the Cerrado Biome in the Brazilian Midwest, a hotspot area and where the highest disease levels have been recorded. Forty eight host lines exhibiting moderate to high resistance to the disease included synthetic hexaploid wheat genotypes (SHW) and derivatives (17), breeding lines (16), landraces (2), and cultivars (13). Thirty early genotypes were identified to have head blast incidence levels similar to the moderately resistant cultivar BR 18. In addition, seven medium maturing genotypes and ten late maturing genotypes had average disease incidence scores on spikes below 35%. These were grouped separately from all other materials. This study also indicated a strong correlation between head blast incidence and yield loss, indicating that incidence could be an appropriate selection parameter in breeding programs targeting blast resistance.

Genome-wide association study of multiple traits linked to heat tolerance in emmer-derived hexaploid wheat genotypes.

The online version contains supplementary material available at 10.1007/s11032-021-01222-3.

Wheat breeding highlights drought tolerance while ignores the advantages of drought avoidance: A meta-analysis

Crop tolerance and avoidance are critical adaptation mechanisms to cope with drought stress but they contribute differently to grain yield formation. Little is known about the different roles of these two mechanisms in long-term crop breeding. A meta-analysis was conducted to determine the different effects of drought tolerance and avoidance mechanisms on the drought adaptation of wheat crops. The meta-analysis summarized the results of 283 published papers in international journals, and illustrated that primitive wheat genotypes, including wild, cultivated diploids, tetraploids and old hexaploids, preferentially showed a drought avoidance strategy, as evidenced by large root biomass, small leaf area, and reduced stomatal conductance under water deficits. Modern hexaploid genotypes showed stronger drought tolerance advantages, such as high leaf water potential and osmotic adjustment, with a small root system. The meta-analysis indicated that the breeding process of dryland wheat has been continuously enhancing drought tolerance while weakening drought avoidance. Under severe water deficits, old hexaploid wheat genotypes with drought avoidance characteristics showed lower reduction of aboveground biomass and yield than modern genotypes with stronger drought tolerance features, while under mild and moderate water deficits genotypes with stronger drought tolerance features had higher yields and aboveground biomass. The meta-analysis provide information for making decisions on the direction of modern crop breeding and the implementing of managing practices to cope with drought stress, which frequency and severity is increasing with the advent of climate change.

Implications of emmer (Triticum dicoccon Schrank) introgression on bread wheat response to heat stress

Wheat is sensitive to heat stress, particularly during grain filling, and this reduces grain yield. Ancestral wheat species, such as emmer wheat (Triticum dicoccon Schrank), represent potential sources of new genetic diversity for traits that may impact wheat responses to heat stress. However, the diversity available in emmer wheat has only been explored superficially. Recently developed emmer derived hexaploid wheat genotypes were evaluated for physiological, phenological and agronomic traits in a multi-environment, multi-season strategy. The emmer-based hexaploid lines were developed from crosses and backcrosses to 9 hexaploid recurrent parents and these genotypes and 7 commercial cultivars were evaluated under two times of sowing (E1 and E2) in the field for three consecutive years (2014–2016). The materials were genotyped using a 90 K SNP platform and these data used to estimate the contribution of emmer wheat to the progeny. Significant phenotypic and genetic variation for traits were observed. Higher temperature during reproductive development and grain filling reduced trait expression. Emmer progeny with greater trait values than their recurrent parents and commercial cultivars in both environments were found. Derivatives with higher physiological trait values yielded well in both environments; as indicated by the clustering of genotypes. The emmer wheat parent contributed between 1 and 43 % of the genome of the emmer-based hexaploid progeny, and progeny with greater emmer contribution had superior trait values in both environments. These results showed a positive effect of direct emmer introgression on wheat performance under heat stress. Mitigation of high temperature stress through the introgression of favorable alleles from wheat close relatives into modern wheat cultivars is possible.

Phenolic compounds and allelopathic activities of ancient emmer wheats: perspective for non-chemical weed control scenarios

Phenolic compounds are natural phytotoxins which play role as chemical defense compounds in wheat species. However, the contribution and role of phenolic compounds in ancient and modern wheat genotypes for plant-to-plant interference are equivocal. Biological screening of seven wheat genotypes including five emmer wheat genotypes of Triticum turgidum ssp. dicoccum (Zarneh, Singerd, Shahrekord, Khoygan and Joneghan), one modern hexaploid wheat genotype (Triticum aestivum var. Roushan) and one modern tetraploid wheat genotype (Triticum turgidum var. Yavaroos) demonstrated that all wheat genotypes suppressed the seedling growth of Raphanus sativus L. by shoot aqueous extract in a dose–response bioassay. Modern hexaploid wheat genotypes along with ancient tetraploid emmer wheat genotypes possessed a high allelopathic capability. High-performance liquid chromatography diode array detection analysis of aqueous extracts indicated that the ability to synthesise polyphenolic compounds is different among genotypes. The total amount of polyphenolics and flavonoid compounds in shoot aqueous showed a significant correlation to the R. sativus growth suppression. These results suggest that the number of polyphenolics in general and syringic acid in particular may have contributed to the allelopathic effects of ancient tetraploid and modern hexaploid wheat genotypes. At the same time, results showed that ancient tetraploid emmer wheat may offer promising values for their unique composition of allelochemicals, indicating their potential in sustainable crop production systems.

Assessment of Crossability between Tetraploid and Hexaploid Wheat Genotypes and Evaluating their Hybrids for Salinity Tolerance

The present study aimed to investigate the crossability differences among three tetraploid durum and three hexaploid bread wheat genotypes and to study the chromosome number and meiotic behavior of their pentaploid F1 hybrids and F2 plants. The parental genotypes and their F1 hybrids were also evaluated for salinity tolerance at seedling stage under 0 and 100 mM NaCl concentrations. The results showed high significant differences in the crossability (%) among the interspecific crosses as well as between direct and reciprocal crosses. The crossability (%) was high when the tetraploid species were used as maternal parents (direct crosses). The pentaploid F1 hybrids had a chromosome complement of 35 chromosomes and showed abnormal meiotic behavior in different stages of meiosis. Cytogenetic analysis of F2 plants revealed high variations in chromosome number within and among the tested F2 populations, however some plants with 2n = 42 chromosomes were recorded. On the other hand, salinity stress affected durum wheat parents and their tetraploid hybrids higher than its effect on hexaploid wheat parents and their hexaploid hybrids for all studied traits. However, in general, pentaploid F1 hybrids showed moderate reductions for all studied traits compared to their parents. Additionally, they were more tolerant to salinity as compared to their tetraploid parents, suggesting that salinity tolerance genes of the bread wheat parents were transmitted to their pentaploid F1 hybrids. Thereby, the pentaploid hybrid strategy used in the present study could be an effective tool to transfer desirable genes and traits between tetraploid and hexaploid wheat species.

Genetic Diversity and Traits Association in Tetraploid and Hexaploid Wheat Genotypes in Khyber Pakhtunkhwa Province of Pakistan

Genetic Diversity and Traits Association in Tetraploid and Hexaploid Wheat Genotypes in Khyber Pakhtunkhwa Province of Pakistan

New protocol for colchicine induced efficient doubled haploidy in haploid regenerants of tetraploid and hexaploid wheats at In vitro level

An investigation to standardize the protocol for in vitro application of colchicine for enhancing the doubled haploid production in wheat was done. Two tetraploid (PDW-314 and A-9-30-1); and two hexaploid (DH-40 and C-306) wheat genotypes were used as maternal parents, whereas, the pollen sources involved Zea mays (cv. Bajaura Makka) and Imperata cylindrica. During the rabi seasons of years 2013–14 and 2014–15, wheat × maize and wheat × I. cylindrica hybridization was carried out followed by treatment of their haploids produced as a result of elimination of chromosomes of maize and I. cylindrica respectively, with varied doses of colchicine for different durations The various doses of colchicine were categorized into two groups: lower doses for longer durations (0.01, 0.025, 0.05% each for 5, 7, 9, 11 hrs) and higher doses for shorter durations (0.05, 0.075, 0.10, 0.15, 0.20, 0.25% each for 5, 4, 3, 2 hrs). The response of different concentrations of colchicine applied for varied durations revealed significant differences for various doubled haploidy parameters viz., per cent survived plants, per cent doubled haploid formation and per cent doubled haploid seed formation. In hexaploid and tetraploid wheats, colchicine doses of 0.075% for 4 hrs and 0.15% for 4 hrs, respectively were established as optimum for enhanced doubled haploid production.