Genetic differentiation and diversity of sugarbeet germplasm resistant to sugarbeet root maggot

Authors: Fugate, Karen; Campbell, Larry; COVARRUBIAS-PAZARAN, GIOVANNY - University Of Wisconsin; RODRIGUEZ-BONILLA, LORRAINE - University Of Wisconsin; Zalapa, Juan

Submitted to: Plant Genetic Resources
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/18/2019
Publication Date: 11/15/2019
Citation: Fugate, K.K., Campbell, L.G., Covarrubias-Pazaran, G., Rodriguez-Bonilla, L., Zalapa, J.E. 2019. Genetic differentiation and diversity of sugarbeet germplasm resistant to sugarbeet root maggot. Plant Genetic Resources. 17(6):514-521. https://doi.org/10.1017/S1479262119000388.
DOI: https://doi.org/10.1017/S1479262119000388

Interpretive Summary: The USDA breeding program in Fargo, ND has developed five sugarbeet varieties (F1015, F1016, F1024, F1043, and F1055) with resistance to the sugarbeet root maggot (SBRM), the most devasting insect pest of sugarbeet in North America. However, to effectively use these varieties in commercial breeding programs for the production of SBRM-resistant hybrids requires knowledge of the strength of SBRM resistance of each variety and knowledge of the genetic differences and similarities between varieties. Therefore, field studies were conducted to compare the level of SBRM resistance between resistant varieties and a study was undertaken to measure the level of genetic variability between and within varieties. SBRM damage was significantly reduced in all resistant varieties tested. SBRM resistance was similar in F1016, F1024, F1043, and F1055 and these varieties had greater SBRM resistance than F1015. F1016, F1024, and F1055 exhibited genetic similarities, while F1015 and F1043 were genetically distinct from these three varieties. With similar levels of SBRM resistance and similar genetics, F1016, F1024, and F1055 are expected to be equally effective in introducing SBRM resistance into commercial hybrids. F1043, with similar SBRM resistance but distinct genetics, provides sugarbeet breeders an alternative, genetically unique source of SBRM resistance for the development of SBRM-resistant sugarbeet hybrids.

Technical Abstract: Germplasm lines with resistance to the sugarbeet root maggot (SBRM) have been developed and released to the public, providing a means to generate hybrids with resistance against the most devasting insect pest of sugarbeet in North America. Effective use of this germplasm, however, requires knowledge of relative strengths of SBRM resistance between lines and knowledge of the diversity and genetic relationships between germplasm. Therefore, field studies comparing SBRM resistance of four released SBRM-resistant germplasm lines (F1015, F1016, F1024, and F1043), a SBRM-resistant parent (PI 179180), and an unreleased SBRM-resistant population (F1055) were performed, and genetic analysis of the diversity and relationships between SBRM-resistant germplasm and their available parents was conducted using simple sequence repeat (SSR) markers. Under natural SBRM infestations, resistant germplasm exhibited significantly less SBRM damage than a susceptible control, with similar, high levels of resistance in F1016, F1024, F1043, F1055, and PI 179180 and lower resistance in F1015. SSR analysis revealed genetic similarities between F1016, F1024, and F1055, while F1015 and F1043 were genetically distinct from these lines. Among resistant genotypes, F1015 and F1043 exhibited greatest and least within-line genetic diversity, indicating greater and lesser inbreeding for F1043 and F1015, respectively. Similarities in damage ratings and genetics for F1016, F1024, and F1055 indicate that these lines are likely to be equally effective in introducing SBRM resistance into elite populations and in combining ability. In contrast, F1043, with its unique parentage and genetic dissimilarity from other resistant lines, provides a genetically distinct, but similarly effective, source of SBRM resistance.