Recipient Organization
UNIVERSITY OF DELAWARE
(N/A)
NEWARK,DE 19717
Performing Department
Plant & Soil Science
Non Technical Summary
Every year, billions of dollars in revenue are lost due to crop mechanical failure called lodging. Despite the negative impact of lodging, there is a limited understanding of the plant architectures that contribute to lodging resistance. Recent research, however, has shown that above ground roots, called brace roots, are important in crop anchorage and lodging resistance. Thus, the goal of this research project is to identify the genetic basis of brace root development and function within two agriculturally important crops (Zea mays, commonly known as corn, and Sorghum bicolor, commonly known as sorghum). Further, given that crop production is moving onto marginal lands, a secondary goal of this research project is to identify the impact of environmental stress (such as soil salinity) on brace root development and function. Thus, to meet these goals, I will: 1) grow a population of sorghum genotypes across two years and collect data that describes the variation in brace root traits and function within the population, 2) compare results from sorghum with those of maize to determine if traits are shared among important agricultural crops, 3) prioritize a list of genes that are associated with important brace root phenotypes, and 4) treat a population of sorghum genotypes with saline water and identify how brace root traits are impacted. Ultimately, the findings from this project are necessary for breeding resilient crops and optimizing crop production on marginal lands.
Animal Health Component
25%
Research Effort Categories
Basic
75%
Applied
25%
Developmental
(N/A)
Goals / Objectives
The broad, long-term research goal of this project is to identify the genetic basis of brace root development and function in two agriculturally important crops (Sorghum bicolor and Zea mays). In agriculture, the vertical displacement of stocks (called lodging) negatively impacts the quality and quantity of crop yield. Recent research shows that brace roots positively impact plant anchorage and limit lodging; however, the genetic basis of brace root development and function has not been well established. Specific brace root traits that are important for anchorage and lodging resistance have recently been identified in maize, yet it remains unknown if these traits are important in other cereal crops, such as sorghum. My research aims to fill this knowledge gap and define the genetic basis of brace root development and function in sorghum and maize. This will be the first characterization of brace root phenotypes at a population level in sorghum and the first-time brace root phenotypes and function will be assessed in parallel across genera. Further, quantifying the variation in brace root development and function under abiotic stress is important in the context of future crop production, which is occurring on inhospitable lands. Thus, a second major research goal is to quantify the variation in brace root phenotypes and function in response to salt stress in sorghum. This will be the first assessment of brace root development and function in sorghum under stressed and optimal conditions. Additional goals of this project include gaining experience in publication, teaching, and extension, all necessary skills for obtaining an academic research and teaching position at a land-grant institution. To achieve these goals, I plan to work closely with a postdoctoral mentoring committee consisting of one primary mentor and five external mentors. Specific objectives of the above goals include:Research Objective 1: Characterize the variation in brace root phenotypes (development) within a population of sorghum genotypes.Research Objective 2: Characterize the variation in the brace root contribution to anchorage (function) within a population of sorghum genotypes.Research Objective 3: Identify candidate genes that are associated with brace root phenotypes in sorghum.Research Objective 4: Acquire maize lines with mutations in orthologous genes (UniformMu lines).Research Objective 5: Quantify the variation in brace root phenotypes and function (brace root contribution to anchorage) across the five sorghum landraces.Research Objective 6: Characterize the impact of salt exposure on brace root development (phenotypes) and function (brace root contribution to anchorage) across the five sorghum landraces.Publication Objective 1: Publish high-quality manuscripts from research findings.Publication Objective 2: Present research findings at regional and national conferences.Soft Skills Objective 1: Attend grant writing workshops hosted by the University of Delaware.Teaching Objective 1: Mentor undergraduate students.Teaching Objective 2: Train graduate and postdoctoral researchers on high-throughput data analysis (design/instruct workshop).Teaching Objective 3: Present a guest lecture(s) for undergraduate and graduate students.Extension Objective 1: Present research findings at the Delaware Ag Week/Mid-Atlantic Crop management School.
Project Methods
The first major goal of the proposed project is to identify the shared genetic basis of brace root development and function between sorghum and maize. To address this goal, a population of sorghum genotypes will be planted in replicate plots at the Newark, DE field site during each growing season (May-October) of the proposed project. Each year, 2-4 plots, per genotype, will be planted in a randomized design with each plot containing ~18 seeds. Once brace roots begin to emerge, brace root phenotype data will be collected weekly with a sub-canopy imaging robot (called 'BRobot') that captures high-resolution RGB images. From the RGB images, the following brace root phenotypes will be extracted using a semi-automated pipeline: 1) the number of brace roots per whorl (where whorl 1 is closest to the ground), 2) the single outermost brace root width for the highest whorl in the ground, 3) stalk width, and 4) a right triangle on each side of the plant from the outermost root from highest whorl in the ground. The right triangle will then be used to extract the height of the whorl on the stalk (a leg of a right triangle), the distance from the stalk-to-root grounding (c leg of a right triangle), and the root angle (B angle of the right triangle). The brace root spread width will be calculated as the sum of the stalk width and the b leg from the triangle on both sides of the plant. At the end of the growing season, non-destructive measurements of plant biomechanics will be collected. Three to five plants per plot will be mechanically tested. Plants will be tested once with all brace roots intact and again after the removal of each whorl of brace roots (starting with the top whorl of brace roots). The brace root contribution to anchorage (BRC) will be calculated by comparing the slope of the Force-Deflection curve with all brace roots removed (None), and the slope of the Force-Deflection curve with all brace roots intact (All; BRC=None/All). To determine the most important brace root traits in anchorage within sorghum, supervised modeling approaches will be employed. Specifically, genotypes will be grouped into low, average, or high categories (determined by if they are +/- 1 standard deviation of the mean) for the brace root contribution to anchorage and random forest modeling approaches will be used with brace root phenotypes as predictors. Phenotypes with the highest mean decrease in Gini will be considered the most important predictors of the brace root contribution to anchorage. With the same methods described above, I recently identified the most important brace root traits across 52 maize genotypes (manuscript in revision at Plant, Cell, & Environment). From these methods described above, I will successfully 1) determine the variation in brace root phenotypes within a sorghum population, 2) identify the variation in the brace root contribution to anchorage within a sorghum population, and 3) determine if the same phenotypes that are important for anchorage and lodging resistance in maize are shared within sorghum. Within this same population, I will identify candidate genes that are associated with important brace root traits by comparing genotypes that ranked high and low for the most important predictors (brace root phenotypes) of anchorage. Since the sorghum population has been fully sequenced and sequence information is publicly available, I will leverage this information to identify candidate genes associated with important brace root traits. After prioritizing candidate genes associated with brace root development and function, I will acquire maize lines that contain mutations in orthologous genes from the UniformMu resource. UniformMu mutants will be planted and selfed during the second year of the fellowship to increase seed and ensure genes are homozygous.The second major research goal of the proposed project is to identify the variation in brace root development and function in sorghum in response to salt stress. To test the hypothesis that salt stress delays brace root development and decreases the contribution of brace roots to crop anchorage, 10 sorghum genotypes representative of the five sorghum landraces (caudatum, durra, guinea, kafir, bicolor) will be studied. During year 1 of the proposed project, ten replicates of each landrace will be grown in a controlled greenhouse. Once plants reach the fourth leaf stage of development, five of the ten replicates will be watered daily with non-saline tap water and five of the ten replicates will be watered daily with 75 mM NaCl (methods previously published). The same brace root phenotype data described above (in research goal 1) will be collected weekly via Raspberry Pi mounted cameras on adjustable height rings (The Plant Spinner 2.0; a tool developed by the Sparks Lab). After eight weeks of treatment, plant biomechanics will be tested (as described above) to identify the change in the brace root contribution to anchorage due to salt stress. During year 2 of the proposed project, 20 replicates of each genotype will be grown, and treatment will begin at three staggered time points to determine the effect of plant stage at stress imposition on brace development and function (5 control, 5 treatment 1, 5 treatment 2, 5 treatment 3). As in year 1, the first treatment group will begin at the fourth leaf stage of development and the two additional treatment groups will begin one and two weeks after the initial group. To determine if landrace and the timing of stress impacts brace root development and function, an ANOVA will be used. Additionally, a stress tolerance index (STI) score will be used to identify genotypes that are less impacted by salt stress and the timing of salt stress. From these methods, I will successfully, 1) quantify the variation in brace root phenotypes and function (brace root contribution to anchorage) across the five sorghum landraces, 2) determine the impact of salt exposure on brace root development (phenotypes) and function (brace root contribution to anchorage) across the five sorghum landraces, and 3) identified the variation in brace root development in response to the plant developmental stage during stress application.To evaluate progress, I will meet weekly with Dr. Sparks (primary mentor). At the start of the fellowship, we will prepare an Individual Development Plan (IDP) and outline quarterly goals. During weekly meetings, we will discuss short-term goals related to project progress and during quarterly meetings we will evaluate progress towards project outcomes. Bi-annually, I will meet one-on-one with members of my postdoctoral mentoring committee to receive additional feedback.