Introgression of the cercospora leaf spot (CLS)disease resistance trait from KEMS06 sugar beet germplasm into two double-haploid breeding lines, KDH4-9 and KDH13

Authors: Vincill, Eric; Eujayl, Imad; Majumdar, Raj; Strausbaugh, Carl

Submitted to: Journal of Sugar Beet Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/1/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: One of the most destructive diseases of sugar beet is Cercospora leaf spot (CLS). Epidemics of this disease are reported yearly in the United States sugar beet growing regions causing leaf destruction followed by intensive foliage regrowth. This results in considerable sugar losses despite the application of fungicides throughout the growing season. While progress is being made towards improving the CLS disease resistance in commercially available varieties of sugar beet, CLS disease still remains a significant problem for sugar beet growers. Increasing the genetic resistance in sugar beet has a potential to solve this problem if robust enough CLS disease resistance traits can be identified and rapidly transferred into seed varieties that farmers can use. This report documents the identification of a potentially new CLS disease resistance trait in a sugar beet pre-breeding line (KEMS06) that generated within USDA's sugar beet disease resistance program. We describe the use of greenhouse CLS disease rating assays to characterize the CLS resistance trait, and report that this trait is genetically inheritable into the next generation, providing robust CLS resistance when crossed into other sugar beet breeding lines. In addition, the methods described within this report accelerated our CLS disease resistance trait discovery and development pre-breeding timeline by reducing the time that would normally be required to transfer and fix CLS resistance traits into new sugar beet lines by one to two years.

Technical Abstract: Cercospora beticola Sacc. is the causative agent of Cercospora leaf spot (CLS). CLS is considered one of the most destructive diseases of sugar beet (Beta vulgaris L.) by causing leaf destruction followed by intensive foliage regrowth resulting in considerable sugar losses despite the application of fungicides throughout the growing season. While progress is being made towards improving CLS disease resistance in commercially available varieties of sugar beet, disease-prone areas still require multiple applications of fungicides during the growing season to keep sugar beet crop losses to a minimum. Recently, the sugar beet germplasm KEMS06 (PI 683514) derived from an ethyl methanesulfonate (EMS) mutagenized population was found to have high CLS disease resistance. Sibling cohorts of KEMS06 have shown diverse and tractable phenotypes suggesting that the CLS disease resistance may contain genetic underpinnings that have not been leveraged before in commercial sugar beet varieties. In this report, we describe the use of greenhouse CLS disease assays to characterize the CLS disease resistance trait from the KEMS06 sugar beet germplasm. Two different hybrid (resistant x susceptible) crosses were generated, and the segregation patterns with corresponding variance scores in the successive filial generations were measured. The results presented in this report strongly suggest the CLS disease resistance trait is directly linked to underlying genetic determinants that are segregating in-step across the population in a quantitative manner. Heritability of the KEMS06 CLS disease resistant trait was tractable into the F2, F3, and F4 filial generations. By following a single plant descent methodology—expedited by the use of self-fertility traits in the parental lines—complete introgression of the KEMS06 CLS disease resistance trait was observed in the progeny families. In addition, the methods described within this report accelerated our CLS disease resistance trait discovery and development pre-breeding timeline by reducing the time that would normally be required to introgress and fix disease resistance traits into new sugar beet germplasm by one to two years.