Genetic dissection of maydis leaf blight resistance in maize through QTL mapping

QTL Mapping for Leaf Rust Resistance in a Wheat Recombinant Inbred Line Population of Liang66-S/Hengmai28

Leaf rust (LR), caused by Puccinia triticina, is a major constraint to global wheat production. Identifying quantitative trait loci (QTLs), conferring adult-plant resistance (APR), and developing breeder-friendly markers are essential for durable disease control. In this study, a recombinant inbred line (RIL) population derived from Liang66-S × Hengmai28 was evaluated for leaf rust severity across four environments. Maximum disease severity (MDS) showed continuous variation and moderate to high correlations among environments, indicating polygenic inheritance. Five APR QTLs were mapped on chromosomes 2BL, 3BS, 3BL, 7BL and 7DL, explaining 4.5–9.8% of the phenotypic variance (PVE) with LOD scores of 2.9–7.9. Among these, QLr.DFI-2BL, QLr.DFI-3BS, and QLr.DFI-7BL correspond to previously reported APR loci, whereas QLr.DFI-3BL and QLr.DFI-7DL represent potentially novel loci. QLr.DFI-3BL was detected across all four environments, while QLr.DFI-3BS and QLr.DFI-7BL showed the highest R2 (7.7–8.5% and 8.4–9.8%). Multiple defense-related genes within the QTL intervals for LR were identified, including the putative NBS-LRR, the putative BTB/POZ-MATH, F-box, receptor-like kinase, polyphenol oxidase, calcium-dependent protein kinase, peroxidase, and ethylene-responsive transcription factors. Based on the flanking markers, five KASP markers were developed. K-LR-3BS (for QLr.DFI-3BS) and K-LR-7BL (for QLr.DFI-7BL) successfully genotyped a natural population with 120 accessions, with call rates of 100% and 94.2%, and showed significant association with reduced leaf rust severity. However, further validation in diverse genetic backgrounds and populations is required before they can be considered for routine marker-assisted selection. These results provide two KASP markers as promising markers that require further validation in diverse backgrounds and highlight QLr.DFI-3BS and QLr.DFI-7BL as promising targets for fine mapping and eventual cloning of APR genes in wheat.

Linkage Mapping Study Reveals Conservative QTL and Candidate Genes for Fusarium Ear Rot Resistance in Maize

A recombinant inbred line (RIL) population consisting of 257 progenies was developed by crossing the resistant line BT with the susceptible line Xi502, suggesting their potential association with FER resistance.

Identification of stripe rust resistance loci in Gansu wheat landraces using genome-wide association analysis

Response of tropical maize inbred lines to maize streak virus and major agronomic traits

Maize streak virus (MSV) is a major constraint on maize production in the dry and hot tropics, where susceptible cultivars suffer complete yield loss. The objective of this study was to assess the response of tropical-environment-adapted maize inbred lines for MSV resistance and major agronomic traits to identify parental lines for resistance breeding. Seventy-four inbred lines, including six controls, were evaluated under artificial MSV inoculation over two seasons using an 8 × 10 alpha lattice design. A significant variability (P ≤ 0.05) was detected among genotypes for MSV resistance and yield components. Area under the disease progress curve (AUDPC) ranged from 0.00 to 240.6, disease incidence from 0 to 100%, and grain yield from 0.54 to 4.99 t ha⁻¹. Genotype-by-season interactions were significant for disease incidence and yield-related traits, with most traits showing moderate to high heritability. MSV disease parameters were negatively correlated with grain yield and agronomic traits. Elite parental lines MM05, MM17, MM19, and MM25 were identified as valuable donor parents combining MSV resistance with superior grain yield and favourable agronomic performance. Lines MM10, MM11 and MM72 were identified for hybrid breeding due to their combination of high grain yield and MSV tolerance. Finally, MM36 and MM35 were recognised for their outstanding grain yield performance, attributable to their MSV tolerance. The identified inbred lines provide complementary sources of MSV resistance and represent valuable donor parents for introgression and developing high-yielding MSV-resistant maize hybrids.

GWAS-Guided Development of KASP Markers Associated with Soybean Seedling Resistance to Fusarium solani

Fusarium root rot, primarily caused by Fusarium solani, is a damaging soil-borne disease that restricts soybean growth and reduces yield. In the present study, a panel of 330 soybean germplasm accessions was inoculated with F. solani. Disease responses were evaluated using the disease severity index (DSI). The soybean accessions displayed substantial variation in their susceptibility to F. solani. Based on DSI, 39 accessions were classified as highly resistant, 94 as resistant, 125 as susceptible, and 72 as highly susceptible, accounting for 11.82%, 28.48%, 37.88%, and 21.82% of the panel, respectively. The genome-wide association study (GWAS) was performed using a genotyping dataset of 627,436 high-quality single nucleotide polymorphisms (SNPs) and two models, Fixed and random model Circulating Probability Unification (FarmCPU) and mixed linear model (MLM). Both GWAS models detected putative SNP associations across seven chromosomes. Based on SNP allelic-effect analysis and gene function annotation, eight genes were prioritized and subsequently evaluated by quantitative reverse transcription PCR (qRT-PCR) for their responses to F. solani infection. Two Kompetitive allele-specific PCR (KASP) markers, KASP-S13_37431242 and KASP-S13_37529208, were developed from resistance-associated SNPs on chromosome 13 and evaluated across the diverse soybean association panel used in this study. Accessions carrying the favorable genotypes of these markers were enriched for resistant germplasm, with positive predictive values of 65.52% and 66.67%, respectively, indicating their potential value for preliminary favorable-allele tracking and germplasm prioritization. Collectively, these results improve our understanding of the genomic components underlying soybean responses to F. solani. The identified loci, candidate genes, and KASP assays provide a basis for further functional validation and the development of multi-locus strategies for improving soybean resistance to Fusarium root rot.

Identifying marker-trait associations for wheat stem sawfly resistance

Two novel WSS resistance loci were identified on chromosomes 2B and 5A. Characterization of WSS resistance loci will improve breeders’ ability to select to reduce yield loss due to WSS. Wheat stem sawfly (WSS) is a native grass feeding pest of winter wheat (Triticum aestivum L) which is difficult to control since most of its life cycle occurs within the stem of wheat plants. The only well-characterized genetic resistance to WSS is the solid stem locus (Sst1) on chromosome 3B, which exhibits environmental variability. It is critical to identify novel forms of genetic resistance outside of Sst1 to improve the overall resistance of wheat to WSS. In this study, genome-wide association studies (GWAS) were performed on lines in the Colorado State University wheat breeding program grown between 2014 and 2025 field seasons for three traits of interest: heading date (HD), WSS damage in the form of stem cutting (CUT), and stem solidity (SOLID). Significant marker trait associations (MTA) were identified on chromosomes 2B, 2D, 3A, 3B, 5A, and 5D for CUT and 2A, 3B, 4B, and 6A for SOLID. Significant MTA from these GWAS were used to identify beneficial allelic combinations (AC) for WSS resistance. The stem cutting ACs which had the lowest damage estimates were those in which lines possessed the resistant haplotype at every locus assessed (CUT = 2.35, error = 0.21, N = 56). Lines that had all resistant alleles in the stem solidity ACs showed the same superior estimate (SOLID = 14.7, error = 0.78, N = 22). The positive effects of the identified small-effect MTA on CUT and SOLID indicated the importance of including these loci when breeding for WSS resistance.