Study of Root System Architectural Traits of Oat and Response to Endophyte Inoculation and Drought Stress

Oat is an important cereal crop grown worldwide. Oats have the potential to contribute to human health due to their unique nutritional attributes. Developing oat cultivars with efficient root systems able to extract heterogeneously distributed soil resources can help maintain yield under drought conditions and in nutrient poor soil. Various root traits determine the soil volume that is explored by the root system for resource acquisition. Knowledge about the genetic control of oat root traits and response to biotic and abiotic environmental factors is lacking. Identifying quantitative trait loci associated with root traits and understanding the response of roots to abiotic and biotic environmental factors such as drought and endophytic bacteria may enable plant breeders to develop oat cultivars with efficient roots that can maintain yield under unstable climates. To understand the genetic basis of various root traits in oats and how the oat root and shoot development is impacted by drought and by plant growth-promoting endophytic bacteria, we conducted three different experiments. First, we studied the response of oat root and shoot development to endophytic bacterial inoculation by conducting a root vigor assay and a greenhouse experiment. Several endophytic bacteria significantly increased the root length, root area and root volume for one of the two oat cultivars evaluated in the root xiii vigor assay. The greenhouse study revealed that the response of oat cultivars to endophytic bacterial inoculation varied depending on the growth parameters evaluated, the nitrogen fertilization level, the oat genotype, and their interactions. Thus, identifying a specific strain of bacteria for overall growth promotion in oats might be difficult. To gain a better understanding of the extent of phenotypic differences in roots among oat genotypes and how those variations are controlled genetically, a genome-wide association study of root system architectural traits was conducted. Root traits were phenotyped at the seedling stage using a germination paper-based growth platform and a high-throughput image analysis system. Significant variability in root traits among the 285 genotypes evaluated was observed and broad-sense heritability ranged from 0.17 to 0.59 depending on the trait. We identified 82 significant marker-trait associations using a mixed linear model approach. Markers significantly associated with root traits explained from 7.6 to 19.9 % of the phenotypic variation. We identified multiple candidate genes located close to the significant markers that are known to have a role in root development. Finally, we evaluated the morphological and physiological responses of root and shoot development of ten oat genotypes under drought stress. After withholding watering for two weeks on 21 days old seedlings, we measured chlorophyll content, relative water content, stomatal conductance, stomata number, shoot dry weight, root dry weight, root length, root area, and root volume. Seed yield per plant was also collected by continuing the drying and rewatering cycle until physiological maturity. All traits measured were significantly impacted by the water regime. Oat cultivar Hayden showed the smallest reduction in vigor assay. The greenhouse study revealed that the response of oat cultivars to endophytic bacterial inoculation varied depending on the growth parameters evaluated, the nitrogen fertilization level, the oat genotype, and their interactions. Thus, identifying a specific strain of bacteria for overall growth promotion in oats might be difficult. To gain a better understanding of the extent of phenotypic differences in roots among oat genotypes and how those variations are controlled genetically, a genome-wide association study of root system architectural traits was conducted. Root traits were phenotyped at the seedling stage using a germination paper-based growth platform and a high-throughput image analysis system. Significant variability in root traits among the 285 genotypes evaluated was observed and broad-sense heritability ranged from 0.17 to 0.59 depending on the trait. We identified 82 significant marker-trait associations using a mixed linear model approach. Markers significantly associated with root traits explained from 7.6 to 19.9 % of the phenotypic variation. We identified multiple candidate genes located close to the significant markers that are known to have a role in root development. Finally, we evaluated the morphological and physiological responses of root and shoot development of ten oat genotypes under drought stress. After withholding watering for two weeks on 21 days old seedlings, we measured chlorophyll content, relative water content, stomatal conductance, stomata number, shoot dry weight, root dry weight, root length, root area, and root volume. Seed yield per plant was also collected by continuing the drying and rewatering cycle until physiological maturity. All traits measured were significantly impacted by the water regime. Oat cultivar Hayden showed the smallest reduction in yield in response to drought treatment. Hayden also showed a smaller reduction in relative water content, chlorophyll content, and a strong reduction in stomata number. Results indicated that the larger root system may not necessarily provide a yield advantage under drought conditions in oats. The importance of root mass distribution into lower and upper soil layers should be investigated to improve our understanding of mechanisms involved in coping with drought

Identification of Physiological and Morphological Traits Governing High Water Use Efficiency in Alfalfa

Alfalfa is an important forage crop worldwide. Being deep-rooted, N2-fixing and high yielding, alfalfa has great economic, ecological and nutritional benefits. While alfalfa is a high yielding crop, its high productivity depends on irrigation water in many areas and consumes the greatest amount of water among all the major crops. With a growing demand for water resources due to an increase in human population and industrial water use, plus frequent drought due to climate change, irrigation water has become increasingly scarce and expensive. To sustain high production of alfalfa with limited water resource, alfalfa cultivars with improved water use efficiency (WUE) is urgently needed. As a first step, we started screening alfalfa germplasms for difference in WUE and identified an alfalfa collection, River side (RS), with a greater WUE under drought compared to other ten alfalfa collections. RS is a naturalized alfalfa collected from the Grand River National Grassland in South Dakota. The objective of this study was to identify physiological and morphological traits that may contribute toward higher WUE in RS. Plants were subjected to two water regimes, by supplying either 100% (well-watered) or 50% (water-stressed) of their transpirational water needs. RS showed the smallest stomatal conductance and used the least amount of water under drought compared to other two alfalfa collections, suggesting that a greater WUE in RS is associated with a reduced transcriptional water loss. We found that RS developed smaller but more numerous stomata under drought that might facilitate a more rapid stomatal closure when water is limited but enhance water and nutrient uptake when water is sufficient. RS has also exhibited different changes on two sides of the leaf that may contribute to the regulation of water loss. The abaxial surface developed a greater number of leaf hairs that can potentially increase the boundary layer resistance for transpiration. The adaxial surface developed the stomata with a greater sensitivity to ABA. By examining the leaf epidermal cell size, it is clear that RS showed the greatest reduction in cell size, resulting in a great increase in cell density. The change in cell density may explain an increased stomatal and leaf hair density observed. Our study provided a great insight into the factors that may contribute to a high WUE in alfalfa. We hope that the knowledge developed in this study and in the future study will build a foundation for developing alfalfa with improved WUE

Evaluation of Naked Barley Landraces for Agro-morphological Traits

Naked barley (Hordeum vulgare var. nudum L.) is a traditional, culturally important, climate-resilient winter cereal crop of Nepal. Evaluation of the naked barely genotypes for yield and disease is fundamental for their efficient utilization in plant breeding schemes and effective conservation programs. Therefore, to identify high yielding and yellow rust resistant landraces of naked barley for hilly and mountainous agro-ecosystem, twenty naked barley landraces collected from different locations of Nepal, were evaluated in randomized complete block design (RCBD) with three replications during winter season of 2016 and 2017 at Khumaltar, Lalitpur, Nepal. Combined analysis of variances revealed that NGRC04902 (3.46 t/ha), NGRC00886 (3.28 t/ha), NGRC02309 (3.21 t/ha) and NGRC06026 (3.10 t/ha) were the high yielding landraces and statistically at par with the released variety 'Solu Uwa' (3.15 t/ha). The landraces namely NGRC00837 (ACI Value: 1.86) was found resistant to yellow rust diseases. Landraces NGRC06034 (131.7 days) and NGRC02363 (130.8 days) were found early maturing and NGRC02306 (94.36 cm) was found dwarf landraces among tested genotypes. These landraces having higher yield and better resistance to yellow rust need to be deployed to farmers' field to diversify the varietal options and used in resistant breeding program to improve the productivity of naked barley for Nepalese farmers

Practice and Lived Experience of Menstrual Exiles (Chhaupadi) among Adolescent Girls in Far Western Nepal. December 2018

Background: Menstrual exile, also known as Chhaupadi, is a tradition of “untouchability” in far-western Nepal. Forbidden from touching other people and objects, women and girls are required to live away from the community, typically in a livestock shed, during menstruation. We assessed the lived experiences of Chhaupadi among Nepalese adolescent girls in the far-western Achham district of Nepal, observed the safety and sanitation of their living spaces during Chhaupadi, and assessed the perceptions of local adult stakeholders towards the practice of Chhaupadi. Methods: We collected data from 107 adolescent girls using a self-administered survey in two local schools in Achham. We also conducted a focus group discussion with seven girls, held key informant interviews, and observed the girls’ living spaces during Chhaupadi, using a checklist. Descriptive statistics of the quantitative survey and thematic analyses of qualitative interviews are presented. Results: The majority of the girls (n = 77, 72%) practiced exile, or Chhaupadi, during their menstruation, including 3 (4%) exiled to traditional Chhau sheds, 63 (82%) to livestock sheds, and 11 (14%) to courtyards outside their home. The remaining girls (n = 30, 28%) stayed inside the house, yet practiced some form of menstrual taboos. Of the 77 observed living spaces where the girls stayed during exile, only 30% (n = 23) had a toilet facility. Most exiled girls (97.4%) were restricted from eating dairy products. Participants reported having various psychological problems, including lonliness and difficulty sleeping while practicing Chhaupadi. Three of the girls were physically abused; nine were bitten by a snake. Notably high proportions of the living spaces lacked ventilation/windows (n = 20, 26%), electricity (n = 29, 38%), toilets (n = 54, 70%) and a warm blanket and mattress for sleeping (n = 29, 38%). Our qualitative findings supported our quantitative results. Conclusions: Chhaupadi has been condemned by human rights organizations. While the government has banned the practice, implementation on the ban is proceeding slowly, especially in far-western Nepal. Thus, as a temporary measure, public health professionals must work towards promoting the health and safety of Nepalese women and girls still practicing Chhaupadi

Anchorage of Headed Reinforcing Bars in Concrete

Headed reinforcing bars serve as a viable alternative to hooked bars for anchorage in concrete because they provide a more efficient anchorage mechanism and limit congestion of the reinforcement. This study is part of a comprehensive study of the anchorage behavior of the headed bars. The work described in this report includes tests of 32 No. 8 headed bars anchored in simulated column-foundation joints represented by bars anchored in slabs, all but two with reinforcement in the plane of the slab, and six lapped-slplice specimens without confining reinforcement containing No. 6 headed bars and an analysis of these tests along with test results from 23 studies by other researchers of 84 exterior, seven roof-level interior, and seven knee beam-column joints subjected to reversed cyclic loading. The headed bars in the column-foundation joint specimens had net bearing areas ranging from 4 to 15 times the area of the bar Ab; some of the headed bars contained large obstructions adjacent to the bearing face of the head that exceeded the dimensional limits for HA heads in ASTM A970-16; embedment lengths ranged from 6 to 8.5 in.; reinforcement in a plane perpendicular to the headed bars included combinations of bars placed symmetrically about the headed bar, parallel and close to the long edges of the specimen, bars placed symmetrically about and close to the headed bar in the short direction of the specimen, and bars oriented in both the long and short directions of the specimen; concrete compressive strengths ranged from 4,200 to 8,620 psi; and stresses in the bars at failure ranged from 49,500 to 117,000 psi. The No. 6 headed bars had a net bearing area of 4Ab and a lap length of 12 in. The center-to-center spacing between the spliced bars was 1.67, 2.33, or 3.53 bar diameters db; clear concrete cover to the bars was 2 in.; concrete compressive strengths averaged 6,360 and 10,950 psi; and stresses in the bars at failure ranged from 75,010 to 83,560 psi. For the beam-column joints subjected to reversed cyclic loading, headed bar sizes ranged between D12 (No. 4) and D36 (No. 11), net bearing areas ranged from 1.7 to 11.4Ab, and embedment lengths ranged from 8 to 22.6db; concrete compressive strengths ranged from 3,480 to 21,520 psi and steel yield strengths ranged from 53,650 to 149,930 psi; all but four specimens contained hoops, spaced at 2.2 to 6.8db (1.8 to 5.9 in.), as confining reinforcement parallel to the headed bar within the joint region; clear cover and minimum center-to-center spacing between the bars ranged from 1.4 to 9.9db and from 2 to 11.2db, respectively. Experimental anchorage strengths are compared with values based on descriptive equations for anchorage strength and design provisions for development length of headed bars for members with concrete compressive strengths up to 16,000 psi and steel yield strengths up to 120,000 psi that recognize the contribution of confining reinforcement without specifying minimum limits on bar spacing or clear cover. The descriptive equations and design provisions were developed based on tests of simulated beam-column joints under monotonic loading as part of the comprehensive study. The comparisons are used to expand the applicability of the descriptive equations to members subjected to reversed cyclic loading and develop simplified design guidelines allowing for the use of headed reinforcing bars in wide range of reinforced concrete members. Changes in the provisions of ACI 318-14 for the development length of headed bars and in ASTM A970 for head dimension requirements are also proposed. The results of this study show that reinforcement perpendicular to headed bars in columnfoundation joints does not improve the anchorage strength. Headed bars with obstructions exceeding the dimensional limits for HA heads in ASTM A970-16 provide adequate anchorage strength. Headed bars did not provide sufficient anchorage in knee beam-column joints subjected to reversed cyclic loading. The descriptive equations and proposed design provisions developed based headed bars in beam-column joint specimens tested under monotonic loading, in which the anchorage strength of the headed bar is a function of embedment length, concrete compressive strength, bar spacing, bar diameter, and confining reinforcement within the joint region, are applicable to a wide range of reinforced concrete members, including beam-column joints subjected reversed cyclic loading, lap splices, and column-foundation joints, and allow the minimum clear spacing of 3db between headed bars permitted in joints in special moment frames in accordance with Section 18.8.5.2 of ACI 318-14 to be reduced to 1db, allowing for the use of more closely spaced headed bars. The anchorage strength of the headed bars calculated using anchorage provisions of Chapter 17 of ACI 318-14 with a strength reduction factor of 1.0 provides a very conservative and highly variable estimate of anchorage strength for headed bars compared to the proposed design provisions

Efficacy and Timing of Application of Fungicides, Biofungicides, Host-Plant Defense Inducers, and Fertilizer to Control Phytophthora Root Rot of Flowering Dogwoods in Simulated Flooding Conditions in Container Production

Phytophthora root rot caused by Phytophthora cinnamomi Rands is one of the major diseases of flowering dogwoods (Cornus florida L.). The severity of root rot disease increases when the plants are exposed to flooding conditions. A study was conducted to determine the efficacy and timing of application of different fungicides, biofungicides, host plant defense inducers, and fertilizer to manage Phytophthora root rot in month-old seedlings in simulated flooding events for 1-, 3-, and 7- days. Preventative treatments were drench applied 3 weeks and 1 week before flooding whereas curative treatments were applied 24 hrs. after flooding. Dogwood seedlings were inoculated with P. cinnamomi 3 days before the flooding. Plant height and width were recorded at the beginning and end of the study. At the end of the study, plant total weight and root weight were recorded and disease severity in the root was assessed using a scale of 0-100%. Root samples were plated using PARPH-V8 medium to determine the percentage recovery of the pathogen. Empress Intrinsic, Pageant Intrinsic, Segovis, and Subdue MAXX, as preventative and curative applications, were able to suppress the disease severity compared to the inoculated control in all flooding durations. All treatments, with the exception of Stargus as preventative application 3 weeks before flooding and Orkestra Intrinsic as curative application, were able to suppress the disease severity compared to the inoculated control for 1-day flooding event. Aliette and ON-Gard were effective in the first trial when applied preventatively in both 1 week and 3 weeks before flooding but not in the second trial. Signature Xtra was effective as preventative application but not as a curative application. Interface was effective as curative application but not as preventative application. The findings of this study will help nursery growers to understand the performance of fungicides, biofungicides, host-plant defense inducers, and fertilizer in different time intervals and repeated applications to manage Phytophthora root rot in flooding conditions

Headed Bars in Beam-Column Joints Subjected to Reversed Cyclic Loading

Descriptive equations developed for the anchorage strength of headed bars in beam-column joints under monotonic load are evaluated for beam-column joints subjected to reversed cyclic loading. Test results from 23 studies that include 84 exterior and seven roof-level interior beam-column joints are used in the evaluation. Concrete compressive strengths and reinforcement yield strengths ranged from 3480 to 21,500 psi (24 to 148 MPa) and 53,700 to 150,000 psi (370 to 1030 MPa), respectively. Headed bar sizes ranged from slightly smaller than a No. 4 (No. 13) to No. 11 (No. 36) with net-bearing areas ranging from 1.7 to 8.6 times the bar area. The embedment lengths and center-to-center spacing between the headed bars ranged from eight to 18 bar diameters and from two to eight bar diameters, respectively. Analysis of the test data shows that descriptive equations based on headed bars under monotonic loading are also applicable to headed bars in beam-column joints subjected to reversed cyclic loading. These comparisons were used to justify the single approach used within the ACI Building Code for calculating the development length of headed bars

ANCHORAGE OF HEADED REINFORCING BARS IN CONCRETE

Headed reinforcing bars serve as a viable alternative to hooked bars for anchorage in concrete because they provide a more efficient anchorage mechanism and limit congestion of the reinforcement. This study is part of a comprehensive study of the anchorage behavior of the headed bars. The work described in this report includes tests of 32 No. 8 headed bars anchored in simulated column-foundation joints represented by bars anchored in slabs, all but two with reinforcement in the plane of the slab, and six lapped-slplice specimens without confining reinforcement containing No. 6 headed bars and an analysis of these tests along with test results from 23 studies by other researchers of 84 exterior, seven roof-level interior, and seven knee beam-column joints subjected to reversed cyclic loading. The headed bars in the column-foundation joint specimens had net bearing areas ranging from 4 to 15 times the area of the bar Ab; some of the headed bars contained large obstructions adjacent to the bearing face of the head that exceeded the dimensional limits for HA heads in ASTM A970-16; embedment lengths ranged from 6 to 8.5 in.; reinforcement in a plane perpendicular to the headed bars included combinations of bars placed symmetrically about the headed bar, parallel and close to the long edges of the specimen, bars placed symmetrically about and close to the headed bar in the short direction of the specimen, and bars oriented in both the long and short directions of the specimen; concrete compressive strengths ranged from 4,200 to 8,620 psi; and stresses in the bars at failure ranged from 49,500 to 117,000 psi. The No. 6 headed bars had a net bearing area of 4Ab and a lap length of 12 in. The center-to-center spacing between the spliced bars was 1.67, 2.33, or 3.53 bar diameters db; clear concrete cover to the bars was 2 in.; concrete compressive strengths averaged 6,360 and 10,950 psi; and stresses in the bars at failure ranged from 75,010 to 83,560 psi. For the beam-column joints subjected to reversed cyclic loading, headed bar sizes ranged between D12 (No. 4) and D36 (No. 11), net bearing areas ranged from 1.7 to 11.4Ab, and embedment lengths ranged from 8 to 22.6db; concrete compressive strengths ranged from 3,480 to 21,520 psi and steel yield strengths ranged from 53,650 to 149,930 psi; all but four specimens contained hoops, spaced at 2.2 to 6.8db (1.8 to 5.9 in.), as confining reinforcement parallel to the headed bar within the joint region; clear cover and minimum center-to-center spacing between the bars ranged from 1.4 to 9.9db and from 2 to 11.2db, respectively. Experimental anchorage strengths are compared with values based on descriptive equations for anchorage strength and design provisions for development length of headed bars for members with concrete compressive strengths up to 16,000 psi and steel yield strengths up to 120,000 psi that recognize the contribution of confining reinforcement without specifying minimum limits on bar spacing or clear cover. The descriptive equations and design provisions were developed based on tests of simulated beam-column joints under monotonic loading as part of the comprehensive study. The comparisons are used to expand the applicability of the descriptive equations to members subjected to reversed cyclic loading and develop simplified design guidelines allowing for the use of headed reinforcing bars in wide range of reinforced concrete members. Changes in the provisions of ACI 318-14 for the development length of headed bars and in ASTM A970 for head dimension requirements are also proposed. The results of this study show that reinforcement perpendicular to headed bars in column-foundation joints does not improve the anchorage strength. Headed bars with obstructions exceeding the dimensional limits for HA heads in ASTM A970-16 provide adequate anchorage strength. Headed bars did not provide sufficient anchorage in knee beam-column joints subjected to reversed cyclic loading. The descriptive equations and proposed design provisions developed based on headed bars in beam-column joint specimens tested under monotonic loading, in which the anchorage strength of the headed bar is a function of embedment length, concrete compressive strength, bar spacing, bar diameter, and confining reinforcement within the joint region, are applicable to a wide range of reinforced concrete members, including beam-column joints subjected reversed cyclic loading, lap splices, and column-foundation joints, and allow the minimum clear spacing of 3db between headed bars permitted in joints in special moment frames in accordance with Section 18.8.5.2 of ACI 318-14 to be reduced to 1db, allowing for the use of more closely spaced headed bars. The anchorage strength of the headed bars calculated using anchorage provisions of Chapter 17 of ACI 318-14 with a strength reduction factor of 1.0 provides a very conservative and highly variable estimate of anchorage strength for headed bars compared to the proposed design provisions

Comparative Study of Growth Statistics of Two Species of Paulownia and Optimization of Rooting Methods

Paulownia is a fast-growing woody tree, native to the forests of China. It belongs to the family Scrophulariaceae and is mainly used as a source of wood for furniture and musical instruments. Due to its fast-growing nature and high-quality of wood, there has been growing interest in cultivation and research of Paulownia in Nepal. Growth comparison was performed by measuring shoot length in in vitro condition. Among two species of Paulownia - Paulownia tomentosa (Thunb.) Steud and Paulownia fortuneii (Seem.) Hemsl., the growth rate of P. tomentosa was found to be 0.355 cm/week while that of P. fortuneii was found to be 0.637 cm/week in in-vitro conditions in MS medium supplemented with 0.1 mg/l NAA and 1mg/l BAP. Optimization of rooting methods was also performed, in which, sand rooting was found to be easier and more effective than in-vitro rooting. Dipping the plantlets in 1 mg/l of NAA was found to produce longer and denser roots than lower or higher concentrations during sand rooting

Conventional and High-Strength Headed Bars—Part 2: Data Analysis

Equations to characterize the anchorage strength of headed bars were developed, incorporating key factors affecting anchorage strength: concrete compressive strength; embedment length; bar diameter; spacing between the bars; and confining reinforcement parallel to the headed bars. Results from tests of 138 exterior beam-column joints, 64 without and 74 with confining reinforcement within the joint region, were used to develop the equations. Concrete compressive strengths ranged from 4050 to 16,030 psi (27.9 to 110.6 MPa) and bar stresses at failure ranged from 33,100 to 153,160 psi (228 to 1056 MPa). The bearing area of the headed bars ranged from 3.8 to 9.5 times the area of the bar. Some headed bars contained obstructions adjacent to the head that exceeded the dimensions permitted for HA heads in ACI 318-14 and ASTM A970-13a but are now permitted by ASTM A970-18. The test results show that headed bar anchorage strength is proportional to the concrete compressive strength raised to the power 0.24. The contribution of confining reinforcement is proportional to the area of confining reinforcement parallel to the headed bar within eight to 10 bar diameters of the headed bar. Headed bars with obstructions larger than those permitted in ACI 318-14 that meet the provisions in ASTM A970-18 exhibit anchorage strengths that are similar to those that meet the provisions in ACI 318-14