Location: Tropical Crops and Germplasm Research
2021 Annual Report
Objectives
1. Phenotype exotic sorghum germplasm for important agronomic traits to identify the most valuable accessions for sorghum breeding programs.
1a. Genetically-characterize sorghum accessions from the West-Central African diversity panel (WCADP).
1b. Phenotypically-characterize highly genetically diverse sorghum accessions from the WCADP.
1c. Phenotypically-characterize accessions from NPGS sweet sorghum germplasm.
2. Identify new sources of anthracnose and grain mold resistance through the evaluation of exotic sorghum germplasm from the National Plant Germplasm System (NPGS) sorghum germplasm collection for further introgression breeding.
2a. Identify new sources of host-plant resistance to anthracnose in the WCADP.
2b. Identify new sources of host-plant resistance to grain mold in the WCADP.
Approach
The focus of this research is to use genotypic and phenotypic characterization of National Plant Germplasm System (NPGS) sorghum germplasm to identify new sources of resistance to anthracnose and grain mold in exotic germplam. A total of 396 accessions from West-Central Africa countries will be characterized for host-plant resistance to both diseases followed by genetic characterization through genotype-by-sequence analysis. This information will be combined with phenotypic and genotypic characterization data from sorghum association panels and core subsets from the NPGS Ethiopian and Sudan collections to conduct a large genome wide association analysis. The results will discover new sources of disease resistance and identify novel molecular markers for breeding programs seeking disease resistance. Presently, sweet sorghum varieties utilized as a biofuel source have a narrow genetic base. Therefore, evaluation of sweet sorghum accessions present in the NPGS sorghum collection will be carried out to help to identify new germplasm to broaden genetic variability available for the development of new biofuel varieties of sorghum. For this purpose, a subset of NPGS sweet sorghum germplasm with high Brix values will be characterized for biofuel related traits in conjunction with a subset of the sorghum bioenergy association panel.
Progress Report
In 2021, ARS scientists in Mayaguez, Puerto Rico, conducted multiple field trials to identify new genes for anthracnose, rust, and grain mold resistance. By screening and studying the genetic relationship among tropical sorghum germplasms from Ethiopia, Yemen, Sudan and West African countries, ARS scientists identified genetically diverse anthracnose and grain mold resistance germplasm. Since there is a limited number of resistance sources to both diseases in temperate-adapted germplasm, these novel sources of resistance could be introgressed into temperate adapted germplasm to enhance the narrow genetic diversity that exists in sorghum breeding programs.
ARS scientists in Mayaguez, Puerto Rico, completed the screening of 356 accessions from the National Plant Germplasm System (NPGS) Yemen core collection for anthracnose and grain mold resistance. Based on data from 3 years (2019-2021), scientists identified 28 accessions with resistance to anthracnose. Likewise, 18 accessions that showed high germination rate and low seed deterioration across two years were classified as potential sources of grain mold resistance. In additions, a subset of 66 accessions from the NPGS Ethiopian and Sudan core collection, were evaluated for grain mold resistance of which 15 exhibited high germination rate and low seed deterioration.
To make a better use of the sorghum NPGS germplasm collection and to identify genetically diverse germplasm for sorghum breeding programs, ARS scientists at Mayaguez, Puerto Rico genetically characterized the NPGS Yemen core collection through a genotype-by-sequence (GBS) approach. Scientists found this core collection to be constituted by six populations that were associated with different phenotypic traits. Remarkably, it was found that some anthracnose and grain mold resistance was genetically related and likely to possess similar resistance genes. This analysis allowed ARS scientists to identify which disease-resistant germplasm is the most adequate to be used in future inheritance studies and breeding programs focused on developing new disease-resistant varieties.
The development of temperate-adapted germplasm is necessary to increase the genetic diversity of sorghum breeding programs. In this regard, seven tropical accessions that showed grain mold resistance were crossed with the temperate adapted germplasm RTx430. Through pedigree selection and bulk-population methods ARS scientists in Mayaguez, Puerto Rico, identified 29 lines that exhibited low seed deterioration and/or high germination. These lines are being evaluated in Texas, Florida, and Georgia to determine their flowering and seed quality in temperate regions. These grain mold temperate-adapted resistant lines will provide new germplasm to enhance the genetic diversity of sorghum breeding programs.
Increasing protein content in sorghum could have a beneficial effect in human and animal nutrition. ARS scientists in Mayaguez, Puerto Rico, used a near infrared spectroscopy (NIR) to evaluate the seed of 312 accessions from West-Central African countries and 179 accessions from the Yemen core collection. The 2-yr study found 16 West-Central African accessions and 77 accessions from Yemen with high protein content (<13%). These early results indicate human nutrition in developing countries can be enhanced by the cultivation of these high-protein content accessions. Likewise, food quality of sorghum products could be enhanced using these accessions.
The development of molecular markers linked to anthracnose resistance genes provide a valuable genomic tool for public and private sorghum breeding programs. As part of a grant awarded by the United States Department of Energy, entitled “Uncovering novel sources of anthracnose resistance in population of genetically diverse sorghums”, ARS scientists identified genomic regions in chromosome 6 and 8 associated with anthracnose resistance response in sorghum lines SC265 and SC1103. The sequencing analysis of multiple genes in both genomic regions resulted in the identification of several single nucleotide polymorphism sites (SNPs) and insertion/deletion (INDEL). Three INDEL were used to develop agarose gel molecular markers, while other SNPs are being use for rhAMP genotyping platform. These high throughput molecular markers will be useful in sorghum breeding to increase the selection efficiency of anthracnose resistant plants in segregating populations.
Accomplishments
Review Publications
Prom, L.K., Isakeit, T., Cuevas, H.E., Erattaimuthu, S., Jacobsen, R. 2020. Sorghum seed fungal community and their association with grain mold severity, seed weight, and germination rate. Journal of Agriculture and Crops. 7(1):14-19. https://doi.org/10.32861/jac.71.14.19.
Prom, L.K., Cuevas, H.E., Ahn, E., Isakeit, T., Rooney, W., Magill, C. 2020. Genome-wide association study of grain mold resistance in sorghum association panel as affected by inoculation with Alternaria alternata alone and Alternaria alternata, Fusarium thapsinum, and Curvularia lunata combined. European Journal of Plant Pathology. 157:783-798. https://doi.org/10.1007/s10658-020-02036-3.
