Sorgoleone (Lipophilic Benzoquinones) Levels In The Root Exudates Of Elite Sorghum [Sorghum Bicolor (L.) Moench] Cultivars

Author

Suleica J. Lee, Prairie View A&M University

Date of Award

12-2024

Document Type

Thesis

Degree Name

Master of Science

Degree Discipline

Chemistry

Abstract

Nitrogen loss from cropping systems is significant and is estimated at more than 50% of the amounts applied. Root exudates of certain plant species including sorghum [Sorghum bicolor (L.) Moench] contain sorgoleone which can reduce nitrification and nitrogen loss through biological nitrification inhibition (BNI). Therefore, the goal of this study was to screen selected elite sorghum germplasm comprising hybrids and parents to determine the best sorgoleone secreting cultivars. The hypothesis was that nitrogen loss from croplands could be curbed through exploring sorghum BNI traits. Screening of the cultivars selected was done using an established sorghum culture and extraction pipeline that quantifies sorgoleone, the principal BNI compound in sorghum root hairs.

The procedure involved growing the sorghum cultivars in three replicates, harvesting 6-18 roots per cultivar, and then extracting the sorgoleone with solvents and vacuum centrifuging. Freshly harvested roots were washed with 5 mL of dichloromethane (DCM) to extract the sorgoleone. The roots were dried in parchment bags at 65oC for two days to obtain root dry weights. Next, the DCM was evaporated overnight at room temperature to dry the sorgoleone. The dried out sorgoleone was re-extracted with 500 μL methanol and dried down using speed vacuuming followed by a second extraction with 400 μL methanol. The sorgoleone extract was then dissolved in HPLC-grade acetonitrile for HPLC analysis. The sorgoleone extract was separated using a Schimadzu reverse phase C18 column using isocratic elution. The mobile phase comprised 65% acetonitrile and 35% acidified water (0.5% formic acid). Sorgoleone was detected at 260 nm using a Shimadzu diode-array-detector. Concentrations were determined by comparing the peak area with pure sorgoleone samples with known concentrations.

The sorghum genotypes evaluated showed varied levels of germination. Root biomass produced also varied among genotypes as did sorgoleone. Sorgoleone amounts quantified ranged from 1.8 to 19.1 mg/g of sorgoleone/dry root weight for the sorghum genotypes evaluated. In terms of sorgoleone production, the top genotypes in order of magnitude were PI482903 > R.Tx430 > SC372 > SC265 > SC1345 > B.Tx623 >P898012.

Keywords: Sorgoleone, Sorghum, Sorgoleone, Nitrogen, Biological Nitrification Inhibition, HPLC

Committee Chair/Advisor

Harshica Fernando

Committee Co-Chair

Peter Ampim

Committee Member

Richard W. Griffin

Publisher

Prairie View A&M University

Rights

Date of Digitization

2/19/2025

Contributing Institution

John B Coleman Library

City of Publication

Prairie View

MIME Type

Application/PDF

Recommended Citation

Lee, S. J. (2024). Sorgoleone (Lipophilic Benzoquinones) Levels In The Root Exudates Of Elite Sorghum [Sorghum Bicolor (L.) Moench] Cultivars. Retrieved from https://digitalcommons.pvamu.edu/pvamu-theses/1544