Nandudu Leah, Kawuki Robert, Ogbonna Alex, Kanaabi Michael, Jannink Jean-Luc
Section of Plant Breeding and Genetics, School of Integrative Plant Sciences, Cornell University, Ithaca, NY, United States.
Root crops Department National Crops Resources Research Institute (NaCRRI), Kampala, Uganda.
Front Plant Sci. 2023 Jan 13;13:1099409. doi: 10.3389/fpls.2022.1099409. eCollection 2022.
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.
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.
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.
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.
木薯褐色条纹病（CBSD）是对东非和中非粮食安全的重大威胁。培育抗CBSD品种是应对这一挑战最经济且可持续的方式。
本研究旨在评估（1）国家作物资源研究所第二代群体中CBSD发病率和严重程度的表现；（2）确定与CBSD性状相关的基因组区域；（3）确定感兴趣区域中的候选基因。
共筛选了302个不同的克隆，结果显示整个生长季节的CBSD发病率为44%。叶部和根部症状的严重程度评分在各季节分别为1.28至1.99和1.75至2.28。广义遗传率从低到高（0.15 - 0.96），而狭义遗传率从低到中等（0.03 - 0.61）。在单变量全基因组关联研究（GWAS）分析中，在种植后3个月时，在第1、13和18号染色体上鉴定出5个与CBSD严重程度相关的数量性状基因座（QTL），解释了约19%的表型变异。多变量GWAS分析确定了17个与单变量分析一致的QTL，包括第6号染色体上的其他QTL。在这些区域鉴定出77个基因，其功能包括催化活性、ATP依赖活性、结合、对刺激的反应、翻译调节活性、转运活性等。
这些结果表明第二代群体中毒力存在差异，这主要归因于遗传因素，并且这些QTL区域中注释的基因可能在病毒起始和复制中起关键作用，从而增加了对CBSD的易感性。
