Cassava Brown Streak Disease (CBSD) is one of the most economically important diseases affecting cassava crops in East and Central Africa. Recent studies discovered new sources of resistance from genebank accessions of the world's largest cassava collection safeguarded at Future Seeds, the Americas’ genebank from the Alliance of Bioversity International and the International Center for Tropical Agriculture (CIAT). Seven accessions (COL40, COL2182, COL144, ECU41, PER315, PER353, and PER556) were identified by Sheat et al. (2019) as immune or highly resistant. Plant resistance was detected using a novel and powerful bud grafting technique to evaluate symptoms after inoculation with the most pathogenic virus isolate (CBSV-Mo83) as well as other isolates, followed by virus detection in each sample using quantitative reverse transcription PCR (qRT-PCR). Additionally, 35 accessions potentially resistant were identified by Ospina et al (2024) after screening genotypic data from 5302 accessions of CIAT’s genebank cassava collection. These 35 accessions harbor 1 or 2 favorable genotypes from single nucleotide polymorphic (SNP) markers associated with the resistance. Specifically, four resistance-associated markers that explain between 8-33% of phenotypic variance of CBSD severity or virus presence/absence. The associations were identified by a genome wide association (GWAS) analysis using SNP markers obtained from a genotyping-by-sequencing technique DArTseq and published phenotypic data from Sheat et al (2019) of 234 South American genebank accessions. The germplasm of this subset is useful for research and breeding, to validate and monitor the resistance, identify genes and plant response mechanisms associated with the resistance, evaluate the agronomic and commercial attributes of these accessions and use them as parental lines for breeding.

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Resistance Against Cassava Brown Streak Viruses From Africa in Cassava Germplasm From South America

Genome-wide association study of cassava brown streak disease resistance in cassava germplasm conserved in South America