Genotypic Diversity Research Articles

Prevalence and genotypic diversity of Enterocytozoon bieneusi in pigeons from two parks in Zhengzhou, China.

Enterocytozoon bieneusi is a predominant pathogen that presents significant public health and animal husbandry challenges. Information on the prevalence and genotypes of E. bieneusi in pigeons is scarce. In this study, 207 faecal samples were collected from pigeons in two parks in Zhengzhou, China, and subjected to nested polymerase chain reaction (nested-PCR) analysis for the detection of E. bieneusi. The overall prevalence of E. bieneusi was found to be 15.5% (32/207) across the two parks. ITS sequence analysis identified only the Peru6 genotype (n = 32), which phylogenetic analysis placed within the zoonotic group 1. Among the E. bieneusi isolates, multilocus sequence typing (MLST) at MS1, MS4 and MS7 loci identified 19, 13 and 23 samples, respectively. Of the samples, 11 were successfully amplified and sequenced at all three loci, resulting in nine distinct multilocus genotypes (MLGs). This suggests that pigeons may play a role in the transmission of E. bieneusi to humans and that there is high genetic variability of E. bieneusi in pigeons from Zhengzhou in China.

Assessment of genetic divergence in diverse maize (Zea mays L.) genotypes

Genetic divergence assessed in twenty diverse genotypes of maize (Zea mays L.) using D2 statistics for eleven characters enabled grouping of all the genotypes in five clusters. Test weight, leaf number, harvest index, days to 50 percent flowering and plant height were the major contributors for genetic diversity among the genotypes. Cluster II was the largest contained 6 genotypes followed by cluster III which possessed 5 genotypes. The cluster I, V and IV possessed 4, 3 and 2 genotypes, respectively. Each cluster has different types of genotypes irrespective to their nature of genetic make up belonging to hybrids, composites and land races. The cluster III exhibited maximum intra-cluster distance (30.92), while maximum inter-cluster distance was noted between cluster I and III (91.55).

Assessment of genetic diversity and population structure analysis in Himalayan garlic genotypes from Sikkim using SSR markers.

Garlic (Allium sativum L.) is an important crop with significant medicinal and culinary uses. Understanding the genetic diversity and population structure of Himalayan garlic genotypes from Sikkim is crucial for effective breeding and conservation efforts. This study aims to analyze the genetic diversity among 60 Himalayan garlic genotypes collected from various altitudinal locations of Sikkim, India, using 27 Simple Sequence Repeats (SSR) markers. The genetic diversity was assessed using SSR markers, which revealed substantial variation among the genotypes. The number of alleles (Na) ranged from 1.13 to 2.00, while the major allele frequency (MAF) varied from 0.672 to 0.963. The observed heterozygosity (Ho) ranged from 0.0667 to 0.475, indicating moderate genetic diversity. Population structure analysis using STRUCTURE software grouped the genotypes into three distinct sub-populations, suggesting genetic differentiation not solely based on leaf morphology. Analysis of Molecular Variance (AMOVA) showed that genetic variation was more significant among individuals within populations (41%) than among populations (16%). UPGMA dendrogram and Principal Coordinates Analysis (PCoA) further confirmed the genetic relationships among the genotypes. This study reveals significant genetic diversity among Himalayan garlic genotypes from Sikkim, with clear genetic differentiation observed within and between populations. The results highlight the importance of both leaf morphology types and genetic structure in understanding the genetic basis of phenotypic variation in garlic. The finding provides valuable insights for future breeding programs and conservation strategies, emphasizing the need to consider morphological and genetic data for effective germplasm management and improvement of garlic cultivars.

Physiological response of diverse maize genotypes to heat stress and simple sequence repeats markers-based genotyping in Rawalpindi, Punjab Pakistan

The current study was designed to observe the response of maize genotypes under high-temperature stress conditions and to check their diversity using simple sequence repeats (SSR) markers in in-vitro conditions. Maize genotypes (n=10) were subjected to heat stress at ~45 °C for 72 h after growing into young seedlings. Their physiological responses were determined by measuring the changes in proline content (PC), chlorophyll content (CC), cell membrane stability (CMS), relative water content (RWC) and osmotic potential (Ψπ). The analysed data disclosed significant differences (P ≤ 0.01) among all the characters. Comparison between control and heat-treated genotypes depicted a notable increase in PC, Ψπ while a decrease in CC, RWC and CMS index in heat-treated plants. Maize genotypes viz. NCEV-1230, NARC-4, HN Gold and OPV-20 performed better under heat stress and also showed a strong genetic relationship for similarity index in dendrogram based on selected SSR markers related to abiotic stress tolerance. This study is beneficial for understanding the physiological behaviour of maize plants under heat stress and for further genetic studies on maize to select heat-tolerant lines for breeding programs

Integrating molecular and phenotypic approaches to assess genetic diversity in Heliconia genotypes

Integrating molecular and phenotypic approaches to assess genetic diversity in Heliconia genotypes

Genetic diversity of Bartonella spp. in vampire bats and associated Streblidae bat flies in the Brazilian Amazon.

Among mammals, bats stand out as important reservoirs for Bartonella spp., second only to rodents. In Brazil, out of the 182 species of bats described, three are hematophagous: Desmodus rotundus, Diphylla ecaudata and Diaemus youngii. Considering that Bartonella species have been increasingly associated to disease in humans, the search for such agents in animal reservoirs and ectoparasites is crucial for understanding the epidemiology of bartonelloses. The present study aimed to investigate the occurrence and genetic diversity of Bartonella spp. in vampire bats and Streblidae bat flies in the Brazilian Amazon. For this purpose, 228 spleen samples of D. rotundus and 1 of D. youngi were collected from four states in the northern region of Brazil (Pará (n = 206/D. rotundus; n = 1/D. youngii), Roraima (n = 18/ D. rotundus), Amapá (n = 3/D. rotundus) and Amazonas (n = 1/D. rotundus). Additionally, 142 Streblidae bat flies were collected from 54 D. rotundus (23 Strebla wiedemanni and 118 Trichobius parasiticus) and one D. youngii (1 Trichobius diaemi). Seventy-three (31.9 %; 73/228) spleen samples of D. rotundus (62 from Pará, 9 from Roraima and 2 from Amapá) and 45/142 (31.7 %) Streblidae bat flies (1 T. diaemi, 8 S. wiedemanni and 36 T. parasiticus) were positive in qPCR for Bartonella spp. based on the nuoG gene. Phylogenetic analyses based on the gltA and rpoB genes positioned the sequences obtained together with genotypes previously detected in D. rotundus and bat-associated flies. High genotypic diversity was found among sequences obtained from bats and Streblidae flies (6 gtlA and 11 rpoB genotypes). The genotypes identified in D. rotundus in the present study were exclusively shared with sequences from Bartonella spp. detected in vampire bats, not overlapping with genotypes previously detected in non-hematophagous bats from Brazil. Most of the sequences detected in Streblidae bat flies formed unique genotypes for each dipteran species analyzed. The present study expanded the knowledge regarding the diversity of Bartonella genotypes in vampire bats and associated Streblidae flies.

Recombination landscape and karyotypic variations revealed by linkage mapping in the grapevine downy mildew pathogen Plasmopara viticola.

Plasmopara viticola, the causal agent of grapevine downy mildew, is a biotrophic oomycete engaged in a tight coevolutionary relationship with its host. Rapid adaptation of the pathogen is favored by annual sexual reproduction that generates genotypic diversity. With the aim of studying the recombination landscape across the P. viticola genome, we generated 2 half-sibling F1 progenies (N = 189 and 162). Using targeted SNP sequencing, between 1,405 and 1,894 markers were included in parental linkage maps, and a consensus map was obtained by integrating 4,509 markers. The reference genome could be assembled into 17 pseudochromosomes, anchoring 88% of its physical length. We observed a strong collinearity between parental genomes and extensive synteny with the downy mildew Peronospora effusa. In the consensus map, the median recombination rate was 13.8 cM/Mb. The local recombination rate was highly variable along chromosomes, and recombination was suppressed in putative centromeric regions. Recombination rate was found negatively correlated with repeats' coverage and positively correlated with gene coverage. However, genes encoding secreted proteins and putative effectors were underrepresented in highly recombining regions. In both progenies, about 5% of the individuals presented karyotypic anomalies. Aneuploidies and triploidies almost exclusively originated from the male-transmitted chromosomes. Triploids resulted from fertilization by diploid gametes, but also from dispermy. Obligatory sexual reproduction each year may explain the lower level of karyotypic variation in P. viticola compared to other oomycetes. The linkage maps will be useful to guide future de novo chromosome-scale assemblies of P. viticola genomes and to perform forward genetics.

Prevalence, genotype diversity, and zoonotic potential of bovine rotavirus A in Amhara National Regional State, Ethiopia: A multicenter cross-sectional study

Rotavirus A (RVA) is one of the major viral causes of acute gastroenteritis in calves globally. Bovine RVA can represent a public health concern as it is capable of zoonotic transmission. We assessed the burden, genotype distribution, and zoonotic potential of RVA among calves in Amhara National Regional State, Ethiopia.A multi-center cross-sectional study was conducted involving a total of 266 calves. Clinical data and fecal samples were collected by trained veterinarians. Total RNA was extracted using QIAamp viral RNA mini kit and RVA was detected by One-step qRT-PCR. Amplification and Sanger sequencing of VP7 and VP4 genes were performed to determine G-types and P-types of the circulating RVA, respectively.The prevalence of RVA among calves was 41/266 (15.4%, 95% CI=11.3%-19.5%). The circulating G-types were G6, G8, and G10, while the circulating P-types were P[1], P[4], P[8], P[11], P[13] and P[14]. G10P[11] (37.5%) followed by G6P[14] (18.8%), and G6P[1] (12.5%) were the dominant G/P combinations circulating among calves in the study area. The circulating bovine RVA strains including human-like bovine (GxP[4] and GxP[8]) and porcine-like bovine (G8P[13]) P-genotypes identified in calves were closely related to RVA strains globally reported from bovine, human, caprine, porcine, and other hosts.Our data reveal that the prevalence of RVA in calves is significant with diverse genotypes circulating in the study area with a potential for zoonosis and/or reverse zoonosis. Hence, continuous surveillance of the circulating RVA genotypes is crucial to curb the RVA-associated morbidity and mortality in cattle and human populations.

Genetic Diversity of Field Pea Genotypes (Pisum sativum L.) in Relation to their Plant Type using Multivariate and Genotype-by-Trait Biplot Analysis

Genetic Diversity of Field Pea Genotypes (Pisum sativum L.) in Relation to their Plant Type using Multivariate and Genotype-by-Trait Biplot Analysis

Genetic variability appraisal: Identifying potential chilli Capsicum annuum genotypes through detailed phenotypic analysis for breeding under drought prone regions in Tamil Nadu

Genetic diversity provides a broader genetic pool from which a breeder can select varieties that are resistant to climate change-related challenges. Diverse chilli genotypes are more likely to possess genes that confer resistance to emerging diseases and pests, reducing the need for chemical interventions. This study focused on identifying elite chilli genotypes suitable for rainfed conditions in the North-Western zone of Tamil Nadu, an area prone to dry spells during the growing season. Forty-two chilli genotypes were evaluated for growth and yield parameters, revealing significant variability among them. Genotypes, such as Sidlagatta local (SDL local), Japoni Longi and S2 local, exhibited superior performance in terms of fresh fruit yield, number of fruits per plant, individual fruit weight, fruit length and dry fruit yield. Correlation analysis indicated strong relationships between yield and various fruit characteristics, validating their importance for crop improvement. Principal Component Analysis (PCA) highlighted key traits contributing to genetic variance, such as plant height, number of primary branches and fruit dimensions, aiding in genotype selection for future targeted breeding programs. Cluster analysis grouped the genotypes based on genetic similarity, suggesting potential strategies for hybridization to harness genetic diversity effectively. These findings emphasize the significance of genetic exploration and trait-based selection in enhancing chilli productivity under rainfed conditions amidst changing climatic scenarios.

Wild again: recovery of a beneficial Cannabis seed endophyte from low domestication genotypes

BackgroundBeyond carrying the plant embryo, seeds harbour intricate microbial communities whose transmission across successive plant generations can significantly influence the ecological and evolutionary dynamics of plant–microbe symbioses. The process of plant domestication has potential repercussions in genes involved in plant-microbiome interactions. However, the extent to which breeding can impact the seed microbiome is sparsely explored. Cannabis is a high-value crop but sparsely subjected to agricultural innovations established in other crop species during the last century. Here, we conduct a large-scale analysis of the bacterial seed microbiome of Cannabis across different domestication grades and investigate the potential of seed-associated endophytes as plant growth-promoting agents under both controlled and field conditions.ResultsAnalysis of Cannabis seed endophyte composition and diversity across 46 plant genotypes revealed 813 different bacterial genera with a predominance of Gammaproteobacteria, Bacilli, Actinobacteria and Alphaproteobacteria but a genotype-specific microbiome. The assessment of domestication and breeding on microbial assembly revealed a higher bacterial diversity in low domestication genotypes (Shannon index, H′: 1.21 vs. 1.05) and a higher homogeneity in bacterial composition caused by line development. Further, a seed bacterial isolate (Bacillus frigoritolerans C1141) associated with low domestication genotypes, and with genes associated with bio-fertilization, bioremediation and phytohormone production, increased plant growth by 42.3% at the time of harvest, under field conditions.ConclusionThis study addresses critical knowledge gaps related to the assembly of the Cannabis seed-endophytic microbiome. It reveals that Cannabis breeding is linked to alterations of seed microbial communities, which potentially led to the loss of bacteria with functional significance. These results highlight the importance of preserving seed microbiomes in plant breeding to support sustainable plant health and growth enhancement in Cannabis.CAHvc7HPtw2foEoMit4yw-Video

Metabolite profiling in ten bread wheat (Triticum aestivum L.) genotypes in response to drought stress

Wheat is frequently constrained by extreme environmental conditions such as drought. Improving drought tolerance in wheat genotypes is crucial for ensuring food security, especially considering the challenges posed by climate change. To reveal the involvement of metabolites in drought response, ten diverse wheat genotypes were investigated under control and water scarcity conditions. The field experiments were set-up, using a 5 × 2 alpha lattice design, with two replicates per treatment, in the 2022 and 2023 growing seasons. Metabolites associated with drought tolerance were analysed using ultra-high performance liquid chromatography, coupled with a quadruple time of flight mass spectrometry (UHPLC-qTOF-MS). Multivariate statistical analysis (MVDA) tools, viz. principal component analysis (PCA) and the orthogonal projection to latent structures-discriminant analysis (OPLS-DA) loading scatter plot were used to identify the metabolites that are positively and negatively correlated to drought stress. Significant variation (p < 0.05) among genotypes was observed, with 58 metabolites annotated, including phenolic acids, carbohydrates, and fatty acids. The annotated compounds were linked to thirteen most significant pathways, with one carbon metabolism, cutin, suberin and wax synthesis and starch and sucrose metabolism being significantly affected by water stress, based on the KEGG pathway analysis. The two high-yielding wheat genotypes (LM48 and BW140) under drought stress displayed significant upregulation of key metabolites such as sinapoyl hydroxyagmatine, 7-oxostigmasterol, 1-O-caffeoyl-3-O-p-coumaroylglycerol, and 3-beta-3-lupanol, when compared to the non-stressed conditions. This study demonstrates the prospects of applied metabolomics for chemotaxonomic classification, phenotyping and selection in plant breeding, as well as potential use in crop improvement.

The utilization of CRISPR-Cas9 with human pluripotent stem cell for Parkinson's disease modeling

Abstract. Parkinson's disease (PD), also often referred to as "parkinsonism," is a neurodegenerative disorder. Those afflicted with this condition are frequently elderly, which results in a considerable decline in their quality of life and overall well-being. Although there are major breakthroughs in PD research, there remains an incomplete grasp of the disease's pathogenesis and the formulation of innovative treatment approaches. This has led to an urgent need for a technology that can recapitulate all the features of human PD. The emergence of induced pluripotent stem cells (iPSC) coupled with the rising appeal of Clustered Regularly Interspaced Short Palindromic Repeats and CRISPR-associated protein 9 (CRISPR-Cas9) technology, the construction of PD models through the combination of iPSC and CRISPR-Cas9 has emerged as a crucial area of research in the field of PD. Employing patients' somatic cells, transformed into iPSC and integrated with CRISPR-Cas9 for genetic modification, has facilitated the duplication of the genetic makeup of neural cells associated with PD, thereby facilitating the investigation of the influence of diverse genotypes on disease progression and treatment response. This review outlines the application and future development of iPSC and CRISPR-Cas9 technologies for the study of Parkinson's disease pathogenesis. The technology enables scientists to gain a deeper understanding of PD and paves the way for the development of novel therapeutic approaches in the future.

Genome-wide association of an organic naked barley diversity panel identified quantitative trait loci for disease resistance.

Foliar fungal diseases are a major limitation in organic naked barley (Hordeum vulgare L.) production. The lack of conventional fungicides in organic systems increases reliance on genetic resistance. We evaluated the severity of barley stripe rust (Puccinia striiformis f.sp. hordei Westend), leaf rust (Puccina hordei sp. hordei), spot blotch (Cochliobolus sativus, anamorph Bipolaris sorokiniana (S. Ito & Kurib.) Drechsler ex Dastur), and scald (Rhynchosporium commune Zaffarano, McDonald and Linde sp. November) on a naked barley diversity panel of 350 genotypes grown in 13 environments to identify quantitative trait loci associated with disease resistance. Genome-wide association analyses across and within environments found 10 marker trait associations for barley stripe rust, four marker trait associations for leaf rust, one marker trait association for scald, and five marker trait associations for spot blotch. Structure analysis identified six Ward groups based on genotypic diversity. Resistance to susceptible allele ratios were high for stripe rust and spot blotch, moderate for leaf rust, and low for scald. Combined phenotypic analysis values for each disease overlayed by a principal component analysis found distinct resistance and susceptibility patterns for barley stripe rust and scald. Most significant marker trait associations were previously identified in the literature, providing confirmation and potential new sources of disease resistance for genetic improvement of naked barley germplasm.

Selection of tomato genotypes for organic production systems

ABSTRACT The development of tomato (Solanum lycopersicum L.) varieties adapted to organic production systems is crucial for meeting the demand for organic food and for supporting the sustainable agricultural sector. This study aimed to rescue, evaluate genetic diversity and select tomato genotypes suitable for growing under organic production conditions. To achieve this, the work involved assessing nine table tomato genotypes from different varietal groups in two environments (greenhouse and open field organic conditions). Morpho-agronomic and physical-chemical quality characteristics were evaluated. The experimental design used was a randomised block design with four replications. The data were subjected to analysis of variance, means tests, and Spearman’s correlations. Furthermore, hierarchical dendrograms and principal component analysis were performed to assess morphological variability between genotypes in each of the environments. Dissimilarity dendrograms revealed different clustering patterns under greenhouse and field conditions. In general, the genotypes grown in the greenhouse showed higher commercial yields and organoleptic quality, as well as an earlier crop cycle. The Jumbo, Santa Clara and Kada Gigante genotypes exhibited characteristics that were considered to make them suitable for organic cultivation in both environments, especially in the open field. Gaúcho Marmande presented characteristics (vegetative and physico-chemical) that made it suitable for the open field, while Coração-de-Boi, Bocaina and Roquesso were recommended only for greenhouse cultivation.

Dengue virus genomic surveillance in the applying Wolbachia to eliminate dengue trial reveals genotypic efficacy and disruption of focal transmission

Release of Aedes aegypti mosquitoes infected with Wolbachia pipientis (wMel strain) is a biocontrol approach against Ae. aegypti-transmitted arboviruses. The Applying Wolbachia to Eliminate Dengue (AWED) cluster-randomised trial was conducted in Yogyakarta, Indonesia in 2018–2020 and provided pivotal evidence for the efficacy of wMel-Ae. aegypti mosquito population replacement in significantly reducing the incidence of virologically-confirmed dengue (VCD) across all four dengue virus (DENV) serotypes. Here, we sequenced the DENV genomes from 318 dengue cases detected in the AWED trial, with the aim of characterising DENV genetic diversity, measuring genotype-specific intervention effects, and inferring DENV transmission dynamics in wMel-treated and untreated areas of Yogyakarta. Phylogenomic analysis of all DENV sequences revealed the co-circulation of five endemic DENV genotypes: DENV-1 genotype I (12.5%) and IV (4.7%), DENV-2 Cosmopolitan (47%), DENV-3 genotype I (8.5%), and DENV-4 genotype II (25.7%), and one recently imported genotype, DENV-4 genotype I (1.6%). The diversity of genotypes detected among AWED trial participants enabled estimation of the genotype-specific protective efficacies of wMel, which were similar (± 10%) to the point estimates of the respective serotype-specific efficacies reported previously. This indicates that wMel afforded protection to all of the six genotypes detected in Yogyakarta. We show that within this substantial overall viral diversity, there was a strong spatial and temporal structure to the DENV genomic relationships, consistent with highly focal DENV transmission around the home in wMel-untreated areas and a near-total disruption of transmission by wMel. These findings can inform long-term monitoring of DENV transmission dynamics in Wolbachia-treated areas including Yogyakarta.

Extent and patterns of morphological and molecular genetic diversity and population structure of Nigerian Taro cultivars

BackgroundGenetic diversity is crucial for conservation efforts as well as breeding programs targeted at the development of improved varieties. Taro, a climate-resilient crop, plays a vital role in the nutritional and economic livelihoods of many households in Nigeria, but its yield is very low due to inadequate genetic improvement efforts. A diversity assessment of Nigerian taro is therefore required to create a premise for its improvement in yield, quality and disease tolerance. In this study, the genetic diversity and population structure of 490 taro cultivars comprising two main gene pools: Dasheen (215) and Eddoe (275), collected from farmers and marketers across seven states in Nigeria was assessed using 3047 Diversity Array Technology single nucleotide polymorphism (DArT-SNP) markers. A subset of 114 taro cultivars, comprising 30 Dasheens and 84 Eddoes were further phenotyped using 24 agro-morphological descriptors.ResultsBoth phenotypic and molecular characterization revealed higher genetic diversity among the Eddoes than Dasheens. Estimates of gene flow (Nm = 0.353) revealed intermixing of cultivars among the States of collection, with the highest gene flow occurring between cultivars from Anambra and Ondo states and the lowest between Anambra and Kwara states. Population structure and Ward’s minimum variance hierarchical cluster based on DArT-SNPs identified four groups, one comprising Dasheen and three comprising Eddoe cultivars. Hierarchical clustering based on phenotypic traits delineated three clusters. Variation between gene pools (49%) was higher than within gene pools (32%). Variation among States of collection was high (41%), while variation among individuals within gene pools (18%) and States of collection (19%) was relatively low. Correlation between phenotypic and genotypic diversity assessments was low (r = 0.01), indicating that both approaches were necessary for assessing genetic diversity in taro. However, genotypic assessment provided better information about genetic diversity of the taro cultivars.ConclusionThis is the first study that represented germplasm collection across the major taro growing regions of Nigeria. The findings from this study based on agro-morphological characterization and DArT-SNP genotyping are critical for genetic characterization, conservation and breeding of taro in Nigeria, mainly initiating hybridization between the two genepools after careful assessment of ploidy levels of the accessions collected in this study. This will facilitate in developing improved taro varieties with desirable traits, such as higher yield, better disease resistance, and improved nutritional quality.

Transgressive segregation and the inheritance of paraquat resistance in Canada fleabane (Conyza canadensis)

Abstract Transgressive segregation refers to the phenomenon whereby the progeny of a diverse cross exhibit phenotypes that fall outside the range of the parents for a particular trait of interest. Segregants that exceed the parental values in life history traits contributing to survival and reproduction may represent beneficial new allelic combinations that are fitter than respective parental genotypes. In this research, we use geographically disparate paraquat resistant biotypes of horseweed (Canada fleabane) [Conyza canadensis (L.) Cronquist; syn. Erigeron canadensis L.] to explore transgressive segregation in biomass accumulation and the inheritance of the paraquat resistance trait in this highly self-fertilizing species. Results of this research indicated that the paraquat resistance traits in E. canadensis biotypes originating in California, USA and Ontario, Canada were not conferred by single major gene mechanisms. Segregating generations from crosses among resistant and susceptible biotypes all displayed transgressive segregation in biomass accumulation in the absence of the original selective agent, paraquat. However, when challenged with a discriminating dose of paraquat, progeny from the crosses of susceptible x resistant and resistant x resistant biotypes displayed contrasting responses with those arising from the cross of two resistant biotypes no longer displaying transgressive segregation. These results support the prediction that transgressive segregation is frequently expressed in self-fertilizing lineages and is positively correlated with the genetic diversity of the parental genotypes. When exposed to a new environment, transgressive segregation was observed regardless of parental identity or history. However, if hybrid progenies were returned to the parental environment with exposure to paraquat, the identity of fittest genotype (i.e., parent or segregant) depends on the history of directional selection in the parental lineages and the dose to which the hybrid progeny was exposed. It is only in the original selective environment that the impact of allelic fixation on transgressive segregation can be observed.

Genetic mapping of QTLs for resistance to bacterial leaf streak in hexaploid wheat.

Robust QTLs conferring resistance to bacterial leaf streak in wheat were mapped on chromosomes 3B and 5A from the variety Boost and on chromosome 7D from the synthetic wheat line W-7984. Bacterial leaf streak (BLS), caused by Xanthomonas translucens pv. undulosa poses a significant threat to global wheat production. High levels of BLS resistance are rare in hexaploid wheat. Here, we screened 101 diverse wheat genotypes under greenhouse conditions to identify new sources of BLS resistance. Five lines showed good levels of resistance including the wheat variety Boost and the synthetic hexaploid wheat line W-7984. Recombinant inbred populations derived from the cross of Boost × ND830 (BoostND population) and W-7984 × Opata 85 (ITMI population) were subsequently evaluated in greenhouse and field experiments to investigate the genetic basis of resistance. QTLs on chromosomes 3B, 5A, and 5B were identified in the BoostND population. The 3B and 5A QTLs were significant in all environments, but the 3B QTL was the strongest under greenhouse conditions explaining 38% of the phenotypic variation, and the 5A QTL was the most significant in the field explaining up to 29% of the variation. In the ITMI population, a QTL on chromosome 7D explained as much as 46% of the phenotypic variation in the greenhouse and 18% in the field. BLS severity in both populations was negatively correlated with days to heading, and some QTLs for these traits overlapped, which explained the tendency of later maturing lines to have relatively higher levels of BLS resistance. Markers associated with the QTLs were converted to KASP markers, which will aid in the deployment of the QTLs into elite lines for the development of BLS-resistant wheat varieties.

Genome‐wide association study for powdery mildew resistance in CIMMYT's spring wheat germplasm

AbstractPowdery mildew (PM), caused by Blumeria graminis f. sp. tritici (Bgt), is a foliar disease of wheat (Triticum aestivum) that adversely affects both grain yield and quality. Growing resistant cultivars offers an effective and environmentally sustainable solution to managing PM. However, relying on the same genetic source of resistance can lead to resistance breakdown as Bgt isolates rapidly evolve. To mitigate this, identifying novel resistance sources is crucial. In this study, 225 diverse wheat genotypes were evaluated at adult plant stage in disease nurseries over the three crop seasons (2018/2019, 2019/2020 and 2020/2021). Using disease and genotyping data from 12,160 single‐nucleotide polymorphism (SNP) markers, a genome‐wide association study (GWAS) was conducted to identify novel resistance loci. We identified 22 marker loci significantly (at p &lt; 0.005) associated with PM resistance, distributed across 14 wheat chromosomes (1A, 1B, 1D, 2A, 2B, 2D, 3A, 3B, 4A, 4B, 5D, 6A, 7A and 7B). Of these, seven loci overlap with previously identified regions, while the remaining 15 loci represent novel regions reported for the first time in this study. The identified SNP markers have significant potential for wheat breeding programmes, as they can accelerate the development of PM‐resistant cultivars through marker‐assisted selection.