Genomic Science Program

Plant Feedstock Genomics
for Bioenergy

2009 Awardee

Characterization of Nitrogen Use Efficiency in Sweet Sorghum

INVESTIGATORS: I. Dweikat, T. Clemente, D. Weeks, and J. Yu

INSTITUTIONS: University of Nebraska–Lincoln and Kansas State University-Manhattan

NON-TECHNICAL SUMMARY: Demand for low-input sustainable crop cultivation is increasing to meet the critical need for environment-friendly agriculture. Consequently, developing genotypes with high nutrient use efficiency is one of the major objectives of crop breeding programs. Sweet sorghum (Sorghum bicolor L. Moench) has the potential to augment the increasing demand for alternative fuels by serving as an input efficient, environmentally friendly bioenergy crop. Nitrogen (N) is one the most expensive nutrients to supply; simultaneously, it is the most important factor limiting crop productivity. Approximately 85 to 90 million metric tons of nitrogenous fertilizers are added to soil worldwide each year. Worldwide, nitrogen use efficiency (NUE) for the production of cereals such as wheat, rice, corn, barley, sorghum, millet, oat, and rye is approximately 33 percent. The 67 percent that goes unaccounted for represents a $33 billion annual loss of N fertilizer. An increase in NUE of 10% would result in a savings in excess of $7.5 billion per year. Furthermore, producers are looking for ways to improve their ability to manage N fertilizers more effectively because of recent sharp increases in N fertilizer prices.

OBJECTIVES: The goal of this project is to employ complementary strategies to enhance the ability of sweet sorghum, a potential bioenergy and drought tolerant crop, to become an efficient nitrogen user. To achieve this goal, we will pursue the following specific objectives: (1) Conduct quantitative trait loci (QTL) analysis and marker identification for NUE in advanced grain sorghum populations; (2) Identify loci and specific alleles that control NUE using whole genome and candidate gene association mapping techniques across a diverse set of grain and sweet sorghum accessions.

APPROACH:  Obj. 1. Two inbred sorghum lines, China17and Ck60, have been identified as being tolerant and intolerant, respectively, under low-N stress and comparable adequate-N conditions. China17 uses nitrogen 25 percent more efficiently than most sorghum lines used as parents for hybrid varieties.  The focus of this objective will be to identify the factors in China17 that contribute to its NUE and transfer these factors to sweet sorghum lines that are superior in term of their total biomass production, such as M81E, Grassel, Theis, Keller, Sugar Drip and Della. A subset of 250 F9 plants will be used. Field experiments will be conducted at the University of Nebraska-Lincoln’s Experimental Farms at Mead and Lincoln and will consist of low and nigh N regimes. Plants will be phenotyped for NUE.

Obj. 2.  We have identified two sets of 96 lines in both grain and sweet sorghum by screening for NUE at Mead, NE in an N-starved field. The two sets will be grown both at Mead, NE and Manhattan, KS. Sweet sorghum is similar to grain sorghum except it has a small panicle and produces about 25% of the total grain compared to grain sorghum. Conducting the study using both grain and sweet sorghum should provide some additional insight on the genetics of NUE in both types. Planting, treatments, and phenotypic data collection will proceed as in Obj. 1, and used to perform association analyses for candidate genes involved in N uptake. All plants will be genotyped with simple sequence repeat (SSR) and diversity array technology (DArT) markers, some of which will be selected based on their association with quantitative trait loci (QTL) for NUE. We will also assay for sugar concentration in the sweet sorghum set to determine if N availability has any influence on sugar level in the stalks.  PCR amplification of gene fragments from a subset of 24 lines, followed by sequencing, will be used to discover single nucleotide polymorphisms (SNPs) in 30 to 50 candidate genes involved in NUE.  The identified SNPs will be used to genotype all 192 lines with the Illumina Golden Gate assay.

PROJECT CONTACT:
Name: Ismail Dweikat
Phone: 402-472-5328
Fax: 402-472-7904
Email: idweikat2@unl.edu