Performing Department
(N/A)
Non Technical Summary
There is heavy reliance on nitrogen fertilizers in crop production to supply nitrogen to increase yield. Through nitrification, fertilizer-derived ammoniumis converted to nitriteand nitrateand subsequently lost through denitrification. Nitrogen loss from the cropping system can amount to more than half of the quantity applied. Some plant species secrete compounds that inhibit nitrification in the root zone through biological nitrification inhibition (BNI), which mitigates nitrogen loss and increases its availability. However, exploring this BNI trait to enhance the sustainability of crop production has been largely ignored simply because adding more nitrogen fertilizer to compensate for losses has been easier. But this has led to eutrophication of water bodies and greenhouse gas emissions. Hence the central hypothesis of this integrated and collaborative proposal involving PVAMU and Texas A&M AgriLife Research (TAMAR) is that nitrogen loss and associated nitrogen pollution can be reduced by enhancing the BNI trait in crops. Using the vast sorghum germplasm in the world-renowned TAMU sorghum breeding program (TAMU SBP) and fast phenotyping methods, we propose to (1) determine the best sorgoleone secreting cultivars from existing sorghum hybrids and parents available in the TAMU SBP, (2) use the information generated to identify genomic markers associated with sorgoleone secretion and develop genomic models which can predict sorgoleone secretion, (3) conduct greenhouse and field plot scale studies to confirm nitrogen loss reduction and (4) provide experiential research training for students. The results will be directly applicable to producing nitrogen-efficient sorghum hybrids and will make sorghum agriculture more sustainable.
Animal Health Component
0%
Research Effort Categories
Basic
25%
Applied
50%
Developmental
25%
Goals / Objectives
The goals of the project include:(1) determine the best sorgoleone secreting cultivars from existing sorghum hybrids and parents available in the Texas A& M University Sorghum Breeding Program (TAMU SBP)(2) use the information generated to identify genomic markers associated with sorgoleone secretion and develop genomic models which can predict sorgoleone secretion.(3) conduct greenhouse and field plot scale studies to confirm N loss reduction and(4) provide experiential research training for students
Project Methods
Objective 1. Determine the best sorgoleone secreting cultivars from existing sorghum hybrids and parents available in the Texas A&M UniversitySorghum Breeding Program (TAMU SBP).This objective will be achieved byphenotypingthe parents of recombinant inbred lines (RIL) and Nested Association Mapping (NAM) for the variation in sorgoleone secretion. The progenies of these populations (up to 400) will be screened for BNI secretion to identify the genetic loci that are responsible for contrasting phenotypes. The screening will be doneusinga robust sorghum culture and extraction pipeline we have developed to quantify sorgoleone.Objective 2. Use the information generated to identify genomic markers associated with sorgoleone secretion and develop genomic models which can predict sorgoleone secretion.This objective will be achieved through QTL analysesto identify the genomic regions associated with the sorgoleone secretion trait.The resulting QTL intervals will be screened for potential genes that might influence sorgoleone secretion. Specifically, (1) genes involved in sorgoleone biosynthesis, (2) genes involved in biosynthesis of sorgoleone precursors such as fatty acids and malonyl-CoA, (3) putative transcription factors, and (4) transporters families known to mediate specialized metabolite secretion will be noted. Since it is almostimpossible to narrow down the causative gene for the phenotypic difference simply from QTL analysis, we would explore thetranscriptome of root and root hair. This is because sorgoleone biosynthesis happens exclusively in the root hair, therefore by focusing on the genes that are expressed in this cell type we will be able to further narrow down the candidate genes. In addition, we hypothesize that the gene that is causative for the sorgoleone secretion between the two contrasting parental lines will be differentially expressed in the root hair.The root hair of both parents, as well as the pooled top 20% and bottom 20% progenies for sorgoleone secretion will be isolated, and the transcriptome will be determined through Illumina HiSeq. The reads will be mapped for the current sorghum genome (Sorghum bicolor V.5.1). We will intersect the QTLs with the genes differentially expressed between the high- and low-sorgoleone lines to narrow down the candidate genes that regulate the sorgoleone secretion.Objective 3. Conduct greenhouse and field plot scale studies to confirm N loss reductionGreenhouse studies: Seeds of up to 20 lines identified by our previous work and those identified in Objective 1, or hybrids derived from them, will be tested in a greenhouse. In the greenhouse study, we will use soils collected from fields in two locations (College Station and Thrall, TX). These soils are representative of the type of soil on which sorghum is predominantly grown in the region. Fertilizer (ammonium sulfate) at 50% recommended rate (90 kg ha-1) will be applied at 1 and 6 weeks. The pots will be arranged in a completely randomized design. At 12 weeks, we will destructively sample the soil and plants. The rhizosphere and bulk soil will be separated for N2O emission and potential nitrification studies. Soil properties including pH, EC, NO3-, NO2- and NH4+ will be measured based on established protocols (Schofield and Taylor, 1955; Doane and Horwath, 2003; and Forster, 1995). Finally, above- and below-ground biomass and N content will be measured and NUE will be calculated as [plant N/(fertilizer N + soil N)]. We will select up to 10 contrasting lines to examine their performance in the field. Our rationale is that increased N retention in the root zone will enhance the plant's performance in low N conditions.Field study: to further test the BNI activities for the selected sorghum lines, up to 10 lines or hybrids (depending on the BNI capability in the greenhouse, agronomic performances, and adaptation to the field conditions) will be planted at both Prairie View and College Station, TX locations. Planting and crop management activities will adhere to the guidelines established by Texas A&M AgriLife Extension. Eachgenotype will be treated with either full N rate (100 Ibs N per acre, taking the soil-N at the start into account) or half the N rate. Half of the N will be applied at planting, and the remaining amount will be top-dressed at the 4-5 leaf stage, 25 - 30 days after germination. We will use ammonium sulfate as the fertilizer source due to its significant enhancement of BNI, reported in our previous study as well as those from others. We will use unmanned aerial systems (UAS)-based imaging to track plant growth, physiology, nitrogen use and water efficiency.Remotely sensed images will be collected bi-weekly to determine plant height (Pugh et al., 2018), fractional ground cover (Shi et al., 2016), leaf area index (Shafian et al., 2018), and canopy volume (Cazenave et al., 2019). We have already shown a high correlation between remotely sensed vegetation indices such as the normalized difference vegetation index (NDVI) and LAI and fractional vegetation cover (Fig. 4) (Shi et al., 2016). Multispectral data will also be used for deriving other vegetation indices such as Normalized Difference Red Edge Index (NDRE) soil adjusted NDVI and Enhanced Vegetation Index (EVI). Importantly, NDRE has a very high correlation with aboveground N content.At the booting stage and flowering stage, we will also sample the bulk and rhizosphere soil from each line or hybrid to test the NH4+, NO2-, and NO3- concentration as described for the greenhouse study. In addition, the rhizosphere soil will be incubated with NH4+ to examine the inhibition of nitrification, using established procedures. Collectively, the data obtained from this objective will be used to determine how BNI sorghums behave under full- and low- N conditions, and how BNI affects the soil N composition and plant N absorption.N2Omeasurements in the fieldwill be done using a Fourier transform infrared (FTIR) based multi-gas analyzer (GT 50000 Tera; Gasmet Technology Oy, Helsinki, Finland) following published methods (Kandel et al., 2020; McDonalds et al., 2019).Objective 4. Provide experiential research training for studentsThis objective will be achieved through asix-week summer hands-on research training program to expose and train PVAMU students each summer in Years 2 and 3 in cutting-edge technologies used in plant breeding and cropping systems. Student trainees will be trained and guided to collect relevant data from ongoing experiments to develop presentations. These will be presented at the conclusion of each summer training session. The training will also include professional development spanning topics such ascommunication skills, networking, interpersonal relationships, group process, meeting management, stress management, problem solving and work ethics. The communication skills training will cover technical writing whereby students will be trained to write abstracts, develop posters and oral presentations using research data. They will also be taught how to develop effective resumes and basic interviewing skills.Data AnalysisResearch data collected includinggenomic data (i.e. sequence data to determine difference between parental alleles in the plant population), agronomic including plant growth and health, and yield data, greenhouse gas emissions, soil data as well as BNI secretion datawill be subjected to the appropriate statistical analyses and conclusionsdrawn at the 5% significance level.The undergraduate trainees will be evaluated for technical and soft skills competencies gained using multiple approaches including formal and informal observations, constructive group feedback, positive self-talk and self-assessment tools.