Genetic dissection of cassava brown streak disease in a genomic selection population

Authors: NANDUDU, LEAH - Cornell University; KAWUKI, ROBERT - National Crops Resources Research Institute; OGBONNA, ALEX - Cornell University; KANAABI, MICHAEL - National Crops Resources Research Institute; Jannink, Jean-Luc

Submitted to: Frontiers in Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2022
Publication Date: 1/13/2023
Citation: Nandudu, L., Kawuki, R., Ogbonna, A., Kanaabi, M., Jannink, J. 2023. Genetic dissection of cassava brown streak disease in a genomic selection population. Frontiers in Plant Science. 13:1099409. https://doi.org/10.3389/fpls.2022.1099409.
DOI: https://doi.org/10.3389/fpls.2022.1099409

Interpretive Summary: Cassava brown streak disease (CBSD) is a major threat to food security in East and Central Africa. Breeding for resistance against CBSD is the most economical and sustainable way of addressing this challenge. We evaluated genetic variability for CBSD resistance in cassava. A total of 302 diverse clones were evaluated for symptoms on leaves and roots. The amount of variability explained by genetics depended on the trait and ranged from 3% to 61%. We identified loci in the genome that affected these traits. These results suggest variation in resistance in our population exists and can be useful for breeding.

Technical Abstract: Introduction: Cassava brown streak disease (CBSD) is a major threat to food security in East and central Africa. Breeding for resistance against CBSD is the most economical and sustainable way of addressing this challenge. Methods: This study seeks to assess the (1) performance of CBSD incidence and severity; (2) identify genomic regions associated with CBSD traits and (3) candidate genes in the regions of interest, in the Cycle 2 population of the National Crops Resources Research Institute. Results: A total of 302 diverse clones were screened, revealing that CBSD incidence across growing seasons was 44%. Severity scores for both foliar and root symptoms ranged from 1.28 to 1.99 and 1.75 to 2.28, respectively across seasons. Broad sense heritability ranged from low to high (0.15 - 0.96), while narrow sense heritability ranged from low to moderate (0.03 - 0.61). Five QTLs, explaining approximately 19% phenotypic variation were identified for CBSD severity at 3 months after planting on chromosomes 1, 13, and 18 in the univariate GWAS analysis. Multivariate GWAS analysis identified 17 QTLs that were consistent with the univariate analysis including additional QTLs on chromosome 6. Seventy-seven genes were identified in these regions with functions such as catalytic activity, ATP-dependent activity, binding, response to stimulus, translation regulator activity, transporter activity among others. Discussion: These results suggest variation in virulence in the C2 population, largely due to genetics and annotated genes in these QTLs regions may play critical roles in virus initiation and replication, thus increasing susceptibility to CBSD.