Genome-wide association mapping of fusarium head blight resistance and agromorphological traits in barley landraces from Ethiopia and Eritrea

Fusarium head blight (FHB), caused primarily by Fusarium graminearum, is an important disease of barley (Hordeum vulgare L.), and other cereals. In barley, the genetic basis of FHB resistance has been intensively studied through linkage mapping that identified several quantitative trait loci (QTL). However, our understanding and application of these QTL in breeding is still limited due to the complex nature and low-to-moderate heritability of FHB resistance. Previous studies used either breeding lines, unimproved varieties, or germplasm selections. Here, we used association mapping in barley landraces to identify QTL associated with FHB severity, deoxynivalenol (DON) concentration and correlated agromorphological traits. Diverse barley landraces (n = 298) from Ethiopia and Eritrea were evaluated for the traits under field conditions for 2 yr (2011–2012) in Crookston, MN, and genotyped with 7842 single nucleotide polymorphism (SNP) markers. Association mapping analysis using a mixed model corrected for pairwise relatedness between individuals identified one common resistance QTL on barley chromosome 2HL significantly associated with both FHB severity and DON concentration and another one on 4HL associated with DON concentration. The QTL identified on 2HL is associated with the row-type locus Vrs1. Both of these QTL were not significantly associated with heading date or plant height unlike other QTL reported in previous studies. Thus, the resistant accessions carrying these QTL may be used in breeding programs without the confounding effects from these agromorphological traits. Importantly, these QTL could be new alleles preserved in this unique germplasm, and the linked SNP markers found may be useful in marker-assisted introgression of resistance

Ecology and genomics of an important crop wild relative as a prelude to agricultural innovation

Domesticated species are impacted in unintended ways during domestication and breeding. Changes in the nature and intensity of selection impart genetic drift, reduce diversity, and increase the frequency of deleterious alleles. Such outcomes constrain our ability to expand the cultivation of crops into environments that differ from those under which domestication occurred. We address this need in chickpea, an important pulse legume, by harnessing the diversity of wild crop relatives. We document an extreme domestication-related genetic bottleneck and decipher the genetic history of wild populations. We provide evidence of ancestral adaptations for seed coat color crypsis, estimate the impact of environment on genetic structure and trait values, and demonstrate variation between wild and cultivated accessions for agronomic properties. A resource of genotyped, association mapping progeny functionally links the wild and cultivated gene pools and is an essential resource chickpea for improvement, while our methods inform collection of other wild crop progenitor species

Genetic characterization of multiple disease resistance and agronomical/nutritional traits in hordeum

University of Minnesota Ph.D. dissertation. August 2013. Major: Plant Pathology. Advisor: Dr. Brian J. Steffenson. 1 computer file (PDF); xvi, 293 pages, appendices p. 241-293.Barley is an economically important crop plant whose yield and quality is affected by multiple diseases. Landrace and wild barley gene pools can be utilized to enhance disease resistance and nutrition in cultivated barley. To identify and map resistance loci for three important diseases (stem rust, spot blotch and Fusarium head blight [FHB]), and enhanced accumulation of two vital micronutrients (zinc and iron), genetic mapping was employed. The genetics of resistance to stem rust race TTKSK in Swiss landrace and wild barley accessions at the seedling stage was conducted through bi-parental mapping. Genetic analysis of F2:3 families derived from these accessions revealed that a single gene that maps to chromosome 5HL — at or in close proximity to the complex stem rust resistance locus rpg4/Rpg5 confers resistance. An association mapping approach was utilized to identify Quantitative Trait Loci (QTL) associated with disease resistance and zinc and iron concentration in 298 Ethiopian and Eritrean barley landraces genotyped with 7,842 single nucleotide polymorphism (SNP) markers. For stem rust race TTKSK, five seedling resistance loci were identified: one each on chromosome 2HS, 2HL, 3HL, 4HL, and 5HS. The ones on chromosomes 2HL and 4HL are novel, whereas the other three mapped to regions coincident with previously reported stem rust resistance QTL. For stem rust race MCCFC at the adult plant stage, one locus coincident with a known race TTKSK resistance QTL was identified on chromosome 5HL. For spot blotch, SNP markers located in close proximity with known adult plant spot blotch resistance QTL were found on chromosomes 2HL and 4HS in six-rowed barley landraces. For FHB, one common resistance QTL on chromosome 2HL, also associated with deoxynivalenol (DON) concentration, was identified. A locus mapping to a region of chromosome 4HL, known to contain QTL associated with DON, also was detected. The loci identified on chromosomes 2HL and 4HL associated with FHB and/or DON were not associated with heading date or plant height. Two novel loci associated with grain zinc concentration were identified on chromosomes 4HS and 6HL. For kernel weight, a known QTL region on chromosome 2HL was detected

Epidemiological Characterization of Lettuce Drop (Sclerotinia spp.) and Biophysical Features of the Host Identify Soft Stem as a Susceptibility Factor

The soilborne fungus Sclerotinia minor was not known to produce sclerotia in the stems of infected and uncollapsed Lactuca standing intact until our observation in a greenhouse in 2017. We investigated lettuce–environment–S. minor interactions in two tolerant and four susceptible Lactuca genotypes to determine putative risk factors and targets for disease control. Symptomatological, pathophysiological, developmental, basal stem biophysical, and microclimate responses (27 variables) of the genotypes were determined under field or greenhouse conditions. Distinct patterns of infection responses were observed between modern cultivars and their primitive or wild relatives. Modern cultivars were susceptible to rapid basal stem and root degradations by S. minor. Oilseed lettuce PI 251246 and wild Lactuca serriola 11-G99 were resilient to degradations and significantly deterred mycelium emergence and symptom development but sclerotia formed to a significantly higher height in their stems. Photosynthetic efficiency declined rapidly within 1 day postinoculation (dpi) in susceptible plants but remained intact approximately 5 to 6 dpi in the tolerant 11-G99. Stomatal conductance spiked rapidly in 11-G99 plants within 1 to 3 dpi, coinciding with the emergence of fungal mycelia at the crown. A strong negative correlation detected between basal stem degradation severity or collapse, and stem mechanical strength indicated that stem strength-mediated genetic factors determine the outcome of Sclerotinia infections. Soft stem is a prominent lettuce drop susceptibility factor that could be targeted in resistance breeding and provides the prelude for the analysis of the biological basis of plant architecture-mediated resistance to Sclerotinia spp. in lettuce and other hosts.[Graphic: see text] Copyright © 2021 The Author(s). This is an open access article distributed under the CC BY 4.0 International license

Data from: Ecology and genomics of an important crop wild relative as a prelude to agricultural innovation

Domesticated species are impacted in unintended ways during domestication and breeding. Changes in the nature and intensity of selection impart genetic drift, reduce diversity, and increase the frequency of deleterious alleles. Such outcomes constrain our ability to expand the cultivation of crops into environments that differ from those under which domestication occurred. We address this need in chickpea, an important pulse legume, by harnessing the diversity of wild crop relatives. We document an extreme domestication-related genetic bottleneck and decipher the genetic history of wild populations. We provide evidence of ancestral adaptations for seed coat color crypsis, estimate the impact of environment on genetic structure and trait values, and demonstrate variation between wild and cultivated accessions for agronomic properties. A resource of genotyped, association mapping progeny functionally links the wild and cultivated gene pools and is an essential resource chickpea for improvement, while our methods inform collection of other wild crop progenitor species

Data from: Ecology and genomics of an important crop wild relative as a prelude to agricultural innovation

Domesticated species are impacted in unintended ways during domestication and breeding. Changes in the nature and intensity of selection impart genetic drift, reduce diversity, and increase the frequency of deleterious alleles. Such outcomes constrain our ability to expand the cultivation of crops into environments that differ from those under which domestication occurred. We address this need in chickpea, an important pulse legume, by harnessing the diversity of wild crop relatives. We document an extreme domestication-related genetic bottleneck and decipher the genetic history of wild populations. We provide evidence of ancestral adaptations for seed coat color crypsis, estimate the impact of environment on genetic structure and trait values, and demonstrate variation between wild and cultivated accessions for agronomic properties. A resource of genotyped, association mapping progeny functionally links the wild and cultivated gene pools and is an essential resource chickpea for improvement, while our methods inform collection of other wild crop progenitor species