Plant Sciences

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Research from the Department of Plant Sciences. The department website may be found athttps://www.ag.ndsu.edu/plantsciences

Blizzard Watch is the newsletter for the Department of Plant Sciences and can be found at https://hdl.handle.net/10365/28265

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The Acquisition of Useful Disease Resistance Genes for Hard Red Winter Wheat Improvement
(North Dakota State University, 2015) Poudel, Roshan Sharma
This study was part of a larger pre-breeding effort to develop new parental materials carrying useful genes for disease resistance and adaptation. Firstly, marker-assisted backcrosses were employed to transfer and pyramid combinations of disease resistance genes (Fhb1, Lr34, Lr53, Sr2, Sr26, Sr39, and Sr50) and a reduced height gene (Rht-B1b) into the variety Norstar. Following the third backcross to Norstar, the various backcrossed progenies were inter-mated to derive progenies having combinations of Fhb1 and Rht-B1b plus the targeted leaf and/or stem rust resistance genes. Five NILs (each carrying Fhb1 and Rht-B1b) that differ for the leaf and stem rust resistance genes they possess were recovered. Secondly, a mapping study using the 9K Illumina Infinium iSelect wheat assay was conducted with a F2 mapping population developed by crossing Lr59-25 (0306/2*CSph1b//CSN1AT1B/3/Thatcher) and Superb. Lr59 was mapped 0.5cM distally from the co-segregating SNPs IWA1495, IWA6704, IWA2098 and IWA969 on wheat chromosome arm 6BS.
Adaptation of Quality Protein Maize (Zea Mays L.) to Northern U.S. Corn Belt
(North Dakota State University, 2015) Dong, Naiyuan
There is a need to increase the value of crops and develop the next generation of healthier products. Quality protein maize (Zea mays L.) is an option but has never been adapted to short – season environments. Quality protein maize (QPM) with homozygous embryo and endosperm for mutant allele o2 at the α-zeins regulatory gene opaque-2 shows about 60 to 100% increase in lysine and tryptophan essential amino acids when comparing with non-QPM maize. The objectives of this research were to adapt QPM genotypes to the northern U.S. through the NDSU Early QPM Program, and to evaluate the agronomic potential of early generation QPM lines and hybrids developed by the NDSU maize breeding program for the northern USA. Fifty-four inbred lines, including 47 QPM donor lines from the Iowa State University (ISU) maize breeding program, six experimental lines from the NDSU maize breeding program and one ex-PVP line from industry, were selected to produce 94 early-QPM backcross populations. Based on the earliness, protein content, and amino acid levels of lysine, 218 BC1S2 lines were selected for testcrosses with industry testers. Experiments evaluating testcrosses were arranged in 12 x 12 and 10 x 10 partially balanced lattice designs across three environments in 2013 and 2014. Based on this evaluation, totally 48 S2 lines were selected for further development, 17 of them representing the Stiff Stalk (SS) heterotic group and 31 representing the non-SS-group. Selected lines provided unique advanced inbred lines with hybrid combinations showing not only above average grain yield, dry down, and protein content but also, high levels of lysine, tryptophan, and methionine. The results of this research show, for the first time, the successful adaptation of QPM genotypes to short-season environments. The NDSU maize-breeding program has developed the first high quality maize products through the EarlyQPM and EarlyQPMF (for feedstock) national programs.
Advanced Cropping Systems for Oil and Biomass Feedstock Production in the Northern Great Plains
(North Dakota State University, 2015) Zayas, Alfredo Aponte
Video summarizing a Ph.D. dissertation for a non-specialist audience.
Agronomic Practices that Impact Grain Quality Factors of Durum Wheat (Triticum Turgidum L. Var. Durum Desf.)
(North Dakota State University, 2016) Forster, Shana M.
Durum wheat is a type of wheat primarily used for pasta production. North Dakota is the leading producer of durum wheat in the US with average yields of 2700 kg ha-1. Durum wheat price discounts are common and occur due to disease, heavy metal contamination, and environmental issues that impact grain quality. Studies were conducted in order to determine how agronomic approaches might impact durum quality. Experiments were conducted in order to determine what impact planting date, cultivar, and seeding rate had on the agronomic performance and quality of end-use traits. In general, a delay in planting date resulted in a significant decrease in yield and test weight for all cultivars. Cultivars differed for many of the end-use traits evaluated such as protein content, falling number, and vitreous kernel. Seeding rate had little impact on the traits evaluated. No combination of planting date and cultivar was identified that consistently resulted in grain marketed as US Grade 1 hard amber durum (HAD), or ‘choice durum’. Cultivar selection remains the best option for maintaining end-use traits. The effect of Zn fertilizer source and placement on grain Cd were evaluated. Treatments evaluated had no negative impact on grain yield or test weight. The foliar application of 1.1 kg Zn ha-1 Zn-EDTA in combination with 33 kg N ha-1 in the form of UAN applied at Feekes 10 growth stage (boot stage) resulted in the lowest grain Cd, and highest grain Zn, Fe and protein and represents an approach of biofortification for durum wheat.
Agronomic Studies of Forage Brassicas as Full-Season and Cover Crops for Grazing in North Dakota
(North Dakota State University, 2017) Teuber Winkler, Osvaldo Roberto
Annual forages represent a good feed resource to extend the grazing season into fall and winter, providing a good quality forage for the livestock, allowing more efficient use of rangeland, and at the same time improving soil properties. Many species in the Brassicaceae family are used as forages for grazing. Forage brassicas are characterized by high forage yield, with high nutritive value, low establishment and harvest cost (direct grazing), while providing many ecosystems services. Forage brassicas can be grown as full season forage crops or as cover crops planted after a grain crop. The objectives of this study were: 1) to identify brassicas species and cultivars with high biomass production and forage quality when grown as full-season and as cover crops in North Dakota; 2) to determine their optimum sowing date, plant density and the response to different N and S fertilization rates. Replicated experiments were conducted at four sites Fargo, Prosper, Carrington and Walcott, ND in 2012-2014. Results indicate swede (Brassica napus L. var. napobrassica) and kale [B.oleraceae L. convar. acephala (DC)] were the highest forage yielding brassicas when established in full-season and turnip [Brassica rapa L. var. rapa (L.) Thell).], cv. ‘Appin’ was the highest yielding sown after August. In full-season brassicas, delaying sowing date reduced total forage yield in all species but did not influence forage quality. In brassicas sown after August, total forage yield decreased significantly only in radish in the second sowing date. Plant density did not have an effect on forage yield or N accumulation averaged across environments and species in full-season forage brassicas. This was different in brassicas sown after August, where the highest forage yield was obtained with the highest plant density (≥200 plants m-2). Kale and swede leaf, root/stem, and dead matter yield increased up to 200 kg N ha-1 in a linear response. Sulfur and the interaction between N and S did not have an effect in forage yield and quality. Both full-season and cover crops forage brassicas have great potential as supplemental high quality forage for grazing in North Dakota.
Allelic Relationship of A. strigosa Crown Rust Resistance Factors and their Relationship to Pc38 Suppression
(North Dakota State University, 2018) Ardayfio, Naa Korkoi
An investigation of the suppression effect of Pc38 on Pc94 was conducted by developing F2 segregating populations from genotypes possessing Pc38 and Pc94, together with a population void of the Pc38. Segregating phenotypic ratios were used to determine the crown rust resistance suppression at the Pc38 locus. A Leggett/Df-38 F2 population, possessing no Pc38 gene, produced resistant to susceptible ratios of 3:1 and 2:1. Leggett/Dumont and Leggett/Steele population possessing a copy of Pc38 each, produced resistant to susceptible ratios of 1:3, 1:2 and 3:13. Leggett was the resistant parent possessing Pc94 while Dumont and Steele were the susceptible parents possessing Pc38. Df-38, a susceptible parent, contained neither Pc94 nor Pc38. CR91 was used to identify resistant and susceptible plants in the segregating populations. A factor closely linked to Pc38 or the gene itself was confirmed to suppress the resistance effect of Pc94 in this study. A second experiment was conducted to determine the allelic relationship of crown rust resistance genes in 08BT26-2, 08BT70-1, BT1020-1-1 and BT1021-1-1. The genotypes possessed resistance genes introgressed from A. strigosa similar to Leggett. Leggett is homozygous for Pc94. Four different F2 segregating populations were developed from Leggett by 08BT26-2, 08BT70-1, BT1020-1-1 and BT1021-1-1. A crown rust race virulent to Pc94 was used to determine resistant to susceptible ratios of the populations. Crown rust race 16MN (100- 3) was used to discriminate between resistant and susceptible plants. The allelism test confirmed that the resistance gene present in 08BT26-2 and 08BT70-1 genotypes were the same as Pc94 in Leggett while genotypes BT1020-1-1 and BT1021-1-1 were different.
Altering Grapevine Crop-load and Canopy Architecture Through Cultural and Genetic Methods
(North Dakota State University, 2020) Svyantek, Andrej William
North Dakota's extremely short growing season leads to premature harvest of unripe, high acid grapes with atypical fruit chemistry. To combat the short growing season, grape growers utilize labor intensive grapevine canopy management practices to expose grape clusters to sunshine for enhanced ripening potential. This research examined leaf removal and shoot-thinning, two widely utilized canopy management practices, for their effect on fruit chemistry of two regionally important, cold-hardy grapevines, ‘Frontenac’ and ‘Marquette’. These management techniques were effective at altering fruit chemistry as measured by sugar; however, they are costly to employ commercially due to yield reduction and labor requirements. Furthermore, they rarely impacted the targeted fruit component, acidity of grape must. Ultimately, we sought to mitigate labor expenses associated with on-farm canopy management practices by breeding cold-hardy grapevines with reduced single leaf area. To accomplish this goal, we utilized a novel mutant grapevine with highly dissected, technically compound leaves, ‘Chasselas Cioutat’. After crossing ‘Chasselas Cioutat’ with native, North Dakota isolated, wild riverbank grapes (V. riparia) and two interspecific breeding parents (‘Frontenac gris’ and ‘E.S. 5-8-17’), we observed developmental transitions within leaf shape of young seedling grapevines. Newly emerged leaves became progressively more lobed between main veins as seedlings exited juvenility. However, the targeted compound leaf form was not observed in outcrossed progeny, with one rare exception. For these reasons, grapevines were maintained under greenhouse conditions and advanced to the next generation. Within the first generation of inbreeding, segregation was observed for the distinct compound leaf trait. On-going work to isolate quantitative trait loci is merging genetic maps from multiple sequencing technologies with image analysis to create the first high-resolution understanding of genetic control of compound leaf shape in grapevines. Overall, these efforts have provided the foundation for future breeding aimed at incorporating functional leaf shapes (compound leaf morphology) in the vineyard. Future work in North Dakota grapevine management may need to focus on techniques that promote winter survival and early ripening. Future breeding efforts should continue to focus on the use of novel germplasm material to overcome biotic stresses, improve fruit quality, and increase environmental resistance.
Aminocyclopyrachlor Efficacy on Native Forbs, and Soil Seedbank Change 15 Years Following Release of Leafy Spurge (Euphorbia esula L.) Biological Control Agents
(North Dakota State University, 2016) Thilmony, Blake Marie
Native prairie response to aminocyclopyrachlor (AMCP) was evaluated in the Northern Great Plains. AMCP altered plant communities and reduced foliar cover of introduced, high seral, and low seral forb species. After treatment, high and low seral monocots increased at both sites due to reduced competition from susceptible forbs. AMCP reduced richness, evenness, and diversity. Aphthona spp. were released in the Little Missouri National Grasslands in North Dakota in 1999 for leafy spurge biological control. Soil seedbank composition was sampled from two ecological sites to evaluate changes in the plant community. By 2014, leafy spurge abundance decreased 92% on average. Subsequently, Kentucky bluegrass increased, but has also been deterred by a slow reintroduction of native species. High seral forb species richness has doubled in both ecological sites since 1999. Aphthona spp. successfully controlled leafy spurge for over 15 yr without any additional control methods or costs to land managers.
Aminocyclopyrachlor: Weed Control, Soil Dissipation, and Efficacy to Seedling Grasses
(North Dakota State University, 2012) Conklin, Katie Lynn
Aminocyclopyrachlor was developed for invasive weed control in non-cropland. Weed control, soil dissipation, and seedling grass tolerance with aminocyclopyrachlor were evaluated in field and greenhouse trials. Weed control was evaluated with aminocyclopyrachlor applied at 70 to 210 g ha-1. Absinth wormwood was controlled when treated during vegetative growth, but yellow toadflax was only controlled at flowering. Aminocyclopyrachlor alone did not control houndstongue. Aminocyclopyrachlor dissipation generally increased as either soil moisture or temperature increased. The DT50 values ranged from 3 to > 112 d. Aminocyclopyrachlor applied to cool season grasses at 91 to 112 g ha-1 provided adequate weed control and was safe for use on intermediate wheatgrass, but injured western wheatgrass. Efficacy to green needlegrass could not be determined. Big bluestem, sideoats grama, and switchgrass were difficult to evaluate due to poor grass establishment, but minimal injury was observed when aminocyclopyrachlor was applied at 91 to 168 g ha-1.
Analysis and Identification of QTL for Resistance to Sclerotinia Sclerotiorum in Pea (Pisum sativum L.)
(North Dakota State University, 2018) Ashtari Mahini, Rahil
White mold caused by Sclerotinia sclerotiorumi s one of the most devastating diseases infecting field pea (Pisum sativum L.) which causes severe yield loss worldwide. Population 17 (Lifter/ PI240515), and Population 19 (PI169603/ Medora) were developed by single seed descent and screened by greenhouse evaluation and detached stem assay to identify potential sources of white mold resistance. Twenty-two partial resistant inbred lines were identified with short internode which met at least two resistance criteria based on lesion expansion inhibition (LEI) and nodal transmission inhibition (NTI). To find SNPs (single nucleotide polymorphism) responsible for white mold resistance, Populations 17 and 19 were genotyped using GBS (genotyping by sequencing) methodology and analyzed with the GBS-SNP-CROP pipeline. Linkage maps were constructed for each population and a composite map based on shared SNPs between the two populations was also generated. Nineteen QTL were identified as contributing to resistance to white mold. Seventeen were associated with LEI and two were associated with NTI. The QTL responsible for lesion expansion on LG VII were duplicated in the short internode subset of both populations. Partially resistant inbred lines and QTL responsible for white mold resistance identified in this study can be useful as resources for resistance to S. sclerotiorum in further experiments aimed at developing resistant cultivars.
Association Mapping and Genetic Diversity Studies of Agronomic and Quality Traits in Durum Wheat [Triticum turgidum L. var. durum (Desf.)]
(North Dakota State University, 2017) Johnson, Marina
Genetic diversity studies in breeding programs are important to identify parental lines for hybridization and introgression of desirable alleles into elite germplasm. The genetic diversity analysis of 283 North Dakota State University (NDSU) advanced durum wheat breeding lines developed during the last 20 years indicated that the population was structured according to its breeding history. Total genetic diversity analysis (HT = 0.334) showed adequate level of genetic variation. The results will help in breeding efforts to broaden the genetic base and select lines for crossing as well as for genetic and genomic studies to facilitate the combination of desirable alleles. The quantitative nature of important target traits, combined with environmental effects, makes it difficult to bring the desirable improvement in durum wheat to meet the expectations of all the stakeholders involved in the durum wheat industry. With an objective to identify molecular markers for marker-assisted breeding (MAB), the present study attempted to identify marker-trait associations for six agronomic and 29 quality traits using a genome-wide association study (GWAS) mapping approach. The study used two types of phenotypic datasets, a historic unbalanced dataset belonging to a total of 80 environments collected over a period of 16 years and a balanced dataset collected from two environments, to identify the applicability of historic unbalanced phenotypic data for GWAS analysis. A total of 292 QTL were identified for agronomic and quality traits, with 10 QTL showing major effects (R2 >15%). Over 45% of QTL for agronomic and quality traits were present in both the unbalanced and balanced datasets, with about 50% of those present in both environments in the balanced dataset. Genome-wide association mapping studies identified several candidate markers for use in marker-assisted selection (MAS) for height, gluten strength, distribution of small kernels, polyphenol oxidase (PPO) activity, and yield.
Association Mapping of Agronomic Traits of Dry Beans Using Breeding Populations
(North Dakota State University, 2014) Agarwal, Chiti
Genome wide association mapping (GWAS) is an effective method to fine-map QTL because of its higher mapping resolution. In order to evaluate the possibility of using breeding populations for GWAS, analysis were conducted using AYTs (Advanced Yield Trials) and PYTs (Preliminary Yield Trials) from the NDSU dry bean breeding program, grown in 2012 at four locations in North Dakota using a 6k SNP chip. Genomic regions were evaluated separately for AYT, PYT, AYT+PYT, and races Mesoamerica and Durango. Overall, 13, 11, 9, and 9 significant markers were found for seed yield, maturity, 100-seed weight, and plant height respectively. Two candidate genes for seed yield and four candidate genes for days to maturity were identified. These markers are highly diagnostic within and among NDSU bean breeding populations and therefore, they could be directly used in Marker assisted selection to develop improved bean varieties while maintaining commercially desired phenotypic characteristics of beans.
Association Studies on Pre-Germination Flooding Tolerance and Cell Wall Components Related to Plant Architecture in Dry Bean
(North Dakota State University, 2018) Walter, Katelynn
Dry bean breeding programs have made significant advances in combating both abiotic and biotic stresses as well as improving plant architectural traits via selective breeding. Flooding can cause complete crop loss in dry bean. On the other hand, breeding for an upright architecture in dry bean has been a breeding target in several programs. However, the stem cell wall components underlying this change have yet to be studied. This research focused on analyzing the cell wall components that might be involved in dry bean architecture as well as pre-germination flooding tolerance in dry bean. For the plant architecture study, two significant genomic regions were identified on Pv07 and Pv08 associated with lignin accumulation in dry bean. For the pre-germination flooding study, one unpigmented seed coat genotype (Verano) and three pigmented seed coat genotypes (Indeterminate Jamaica Red, Durango, and Midnight) had germination rates similar to that of the tolerant check.
Biomass Yield and Nutritive Value of Annual Forage Mixes Compared With Monocrops
(North Dakota State University, 2022) Mozea, Kenneth
Forage mixes could serve as a cover crop mix to protect the soil during the winter, for prevented planting areas or as a high nutritious feed for grazing livestock. The objective of this study was to determine the nutritive value and productivity of selected annual forage mixes compared with forage sorghum monocrops. The nutritive value of annual forage mixes and monocrops varied across environments and between treatments. Monocultures produced more biomass than annual forage mixes. The three most productive mixes in comparison to the others were hybrid brassica/oat/forage pea/forage sorghum x sudangrass/sweet sorghum blend/foxtail millet, turnip/forage sorghum x sudangrass/sweet sorghum blend/forage pea/hybrid brassicas/oat/faba bean/forage pea, and forage sorghum x sudangrass/radish mix. The latter being the most cost-effective mix. Forage sorghum dominated annual forage mixes at a planting rate of 2.2 kg/ha. These results emphasize how forage annual mixes can provide additional forage for livestock.
Characterization of Common Wheat Translocations Carrying Leaf Rust Resistance Genes from Alien Species
(North Dakota State University, 2016) Ibrahim, Mohamed Somo
Leaf rust caused by Puccinia triticina Erikss may inflict significant yield losses in wheat; however, can be controlled by breeding for increased host resistance. In earlier studies, effective, resistance has been transferred to common wheat from the wild relatives Thinopyrum ponticum (Lr19), Aegilops sharonensis (Lr56), Ae. peregrina (Lr59), and Ae. neglecta (Lr62). Each translocation was subsequently re-engineered by the induction of homoeologous chromosome exchanges with a normal wheat chromosome to remove unneeded alien chromatin. For each gene the 3-8 most promising recombinants that retained the least linkage drag, but could not be differentiated, were identified. This study employed physical and genetic mapping in conjunction with molecular markers and genomic in situ hybridization to identify those recombinants that are best suited for breeding. For each gene, the recombinant with the least alien chromatin that also appeared to be fully compensating was identified and marker loci suitable for marker-assisted selection were suggested.
Characterization of Selected Winter Hardiness Traits in Pea (Pisum Sativum L.)
(North Dakota State University, 2013) Fiebelkorn, Danielle
Pea (Pisum sativum L.) is an important crop from an agronomic and nutritional standpoint. Winter pea has further agronomic benefits for producers; however, sufficient winter hardiness to survive harsh North Dakota conditions is lacking. Winter hardiness was evaluated in the field and greenhouse using replicated trials with 267 recombinant inbred lines derived from the cross ‘Medora’/‘Melrose’. Similar reactions were observed between the two trials. An optimum protocol based on acclimation time and scoring method to predict winter hardy genotypes using controlled environment conditions was studied. Twelve genotypes were acclimated for 0, 1, 2, 3, and 4 weeks at 4 degrees Celsius prior to being frozen at -8 or -12 degrees Celsius for 1 hour. Three weeks of acclimation and scoring 21 days after freezing provided the best differentiation among genotypes. This research provided direction for development of winter pea varieties suited to the harsh winter conditions of North Dakota.
Characterization of Surfactant Quality and Validation of Standard Water Conditioning Testing
(North Dakota State University, 2018) Adams, Jason Wayland
Adjuvants are products added to pesticide applications to increase pest control. There are many different types of adjuvants designed to solve certain problems. Surfactants are a major class of agricultural adjuvant used to increase the efficacy of pesticides. Many companies use physical and chemical characteristics to market surfactants. However, producers do not understand these characteristics. Field efficacy data should be used to effectively market surfactants, but is somewhat limited. The objective of the first study was to evaluate if chemical and physical characteristics of agricultural surfactants can be used to predict field performance. Chemical and physical characteristics tested included HLB, dynamic surface tension, contact angle, and absorption through isolated cuticles. When individual characteristics were used as covariates with field efficacy data, no consistent results were observed. Therefore, physical and chemical characteristics cannot be used to accurately predict field performance of surfactants. In 2011, Zollinger et al. published a paper titled “A test method for evaluating water conditioning adjuvants” as a standardized test method. While this has been an effective test method, a comparison of salt type used has never been conducted. The objective of this research was to validate the standardized test method using three artificially mixed hard water samples with calcium chloride, calcium formate, and calcium nitrate. Field trials were conducted near Hillsboro, ND in 2016 and 2017. Glyphosate and mesotrione were applied at 342 and 70 g ai ha-1, respectively. Three types of water conditioners were evaluated with glyphosate: diammonium sulfate (AMS), AMS replacement, and monocarbamide dihydrogen sulfate (AMADS). Herbicide antagonism was similar between the simulated hard water samples. Within each type of water conditioning adjuvant, antagonism was overcome similarly in all water types. The results of these studies validate the test method established by Zollinger et al. (2011).
Characterizing Chromosomes for Fusarium Head Blight Resistance in a Spring Wheat (Triticum aestivum L.) Cultivar, 'Frontana'
(North Dakota State University, 2009) Yabwalo, Dalitso Noble
Fusarium head blight (FHB), caused by the fungus Fusarium graminearum, is a major fungal disease of wheat and other cereal crops that causes both yield and quality losses due to shriveled kernels and accumulation of mycotoxins in the seed. 'Frontana', a Brazilian spring wheat cultivar, is a source ofresistance genes to FHB, and it is believed to express resistance to both the establishment and spread of FHB (type I and type II resistance, respectively). Reciprocal backcross monosomic (RBCM) lines developed using Frontana and 'Chris', a susceptible spring wheat cultivar, and involving critical chromosomes 3A, 6A, and 4D from these parents were compared to characterize the type of resistance expressed by Frontana and confirm the chromosomes carrying genes for resistance. In four separate greenhouse tests, spray and single floret inoculation techniques were used to assess both types of resistance. Plants were inoculated when half of the plants in a pot were at anthesis (Feekes Growth Stage 10.5). Genotypes were evaluated for disease incidence, spread, deoxynivalinol (DON) content, Fusarium damaged kernels (FDK) and severity at 21 d after inoculation. Generally, RBCM lines with the critical Frontana chromosomes had low FHB incidence, spread, and severity. The RBCM line with chromosome 3A from Frontana exhibited the lowest FHB severity after spray inoculation, and the least spread after point inoculation. Frontana 3A lines had the lowest FHB incidence levels after spray inoculation amongst the RBCM lines that were tested. This implies the presence of major resistance genes on chromosome 3A which are likely involved in both resistance to disease establishment and spread. However, resistance genes on 3A likely also interact with genes on other chromosomes to confer resistance to FHB because Frontana typically expressed a higher level of resistance to disease establishment and spread. Chromosome 4D also seems to play a significant role in Type I resistance while 6A contributes to Type II resistance.
Characterizing Late Blight Resistance of Parental Genotypes Used in the North Dakota State University Potato Breeding Program
(North Dakota State University, 2022) Bjerke, James
The potato is an important food crop, and late blight is a potato disease costing growers millions of dollars. Utilizing cultivars with late blight resistance is the longest-term option to manage the disease. This two-part study identified genetic resistance to late blight present in North Dakota State University potato germplasm. More than 750 families were screened using a multiyear detached leaf assay. ND8277B-5, Dakota Trailblazer, EB8109-1, ND028856B-1Russ, and Stirling, were found to be the most successful parents. Additionally, 236 clones were evaluated for six late blight resistance (R) genes: R1, R2, R3, RB, Rpi-smira1, and Rpi-ber1. At least one R gene was found in 136 clones. The R1 gene was most prevalent. R1, R2, R3, and RB genes were present in ND14358AB-1, while three R genes were present in Etb 5-31-3 and J101-K6. These evaluations can guide breeding efforts for R gene stacking, developing a durable resistance to late blight.
Cloning and Characterization of the Iron-Regulated Transporter (IRT) Genes and Their Transcription Factors in Populus
(North Dakota State University, 2015) Huang, Danqiong
Iron deficiency causes chlorosis in many plant species, resulting in yield loss and poor quality. Many tree species including poplar are susceptible to iron deficiency. Trees suffering from iron deficiency often show interveinal chlorotic leaves and in severe cases, branches or an entire tree may die. In this study, two trees of Populus tremula L.‘Erecta’ growing near each other but with contrasting leaf color phenotypes were used to study the causes of chlorosis and the mechanisms of tolerance or susceptibility to iron chlorosis in poplar. A leaf analysis revealed that the iron deficiency tolerant tree (PtG) had a higher level of dry matter content, chlorophyll (a+b), Chl a/b ratio, Zn and Fe content than the iron chlorosis susceptible tree (PtY). A hydroponic culture confirmed the differences in aforementioned physiological parameters between PtG and PtY responding to iron deficiency. Two iron-regulated transporter genes (PtIRT1 and PtIRT3), the native promoter of the PtIRT1 gene (PtIRT1-pro), and two basic helix-loop-helix (bHLH) transcription factors (PtFIT and PtIRO) were cloned and characterized for their responses to iron deficiency in PtG and PtY. Deduced amino acid analysis revealed that PtIRT1, PtIRT3, PtFIT, and PtIRO in PtG were identical to those in PtY. Phylogenetic and putative domain analyses showed that PtIRT1, PtFIT, and PtIRO may function in iron homeostasis, while PtIRT3 may play a role in zinc transport in poplar. The expression of PtIRT1 and PtFIT are root-specific and up-regulated by iron deficiency. The expression of a GUS gene derived by PtIRT1-pro in tobacco was also up-regulated by iron deficiency, but was not root-specific. The expression of PtIRT3 is ubiquitous and up-regulated by iron deficiency, but significantly down-regulated by zinc deficiency. A high correlation in the expression between PtFIT and PtIRT1 was observed in PtG, but not in PtY. Transgenic poplars overexpressing PtIRT1 or PtIRT3 did not have enhanced Fe accumulation; however, an enhanced tolerance to iron deficiency was found in transgenic plants overexpressing PtFIT. The results suggested that the transcription factor PtFIT may be involved in iron deficiency response through regulation of PtIRT1 and PtFIT itself may be regulated by other factors in poplar.

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