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Haplotype-resolved genomes of geminivirus-resistant and geminivirus-susceptible African cassava cultivars


Kuon, Joel-E; Qi, Weihong; Schläpfer, Pascal; Hirsch-Hoffmann, Matthias; von Bieberstein, Philipp Rogalla; Patrignani, Andrea; Poveda, Lucy; Grob, Stefan; Keller, Miyako; Shimizu-Inatsugi, Rie; Grossniklaus, Ueli; Vanderschuren, Hervé; Gruissem, Wilhelm (2019). Haplotype-resolved genomes of geminivirus-resistant and geminivirus-susceptible African cassava cultivars. BMC Biology, 17(1):75.

Abstract

Background
Cassava is an important food crop in tropical and sub-tropical regions worldwide. In Africa, cassava production is widely affected by cassava mosaic disease (CMD), which is caused by the African cassava mosaic geminivirus that is transmitted by whiteflies. Cassava breeders often use a single locus, CMD2, for introducing CMD resistance into susceptible cultivars. The CMD2 locus has been genetically mapped to a 10-Mbp region, but its organization and genes as well as their functions are unknown.
Results
We report haplotype-resolved de novo assemblies and annotations of the genomes for the African cassava cultivar TME (tropical Manihot esculenta), which is the origin of CMD2, and the CMD-susceptible cultivar 60444. The assemblies provide phased haplotype information for over 80% of the genomes. Haplotype comparison identified novel features previously hidden in collapsed and fragmented cassava genomes, including thousands of allelic variants, inter-haplotype diversity in coding regions, and patterns of diversification through allele-specific expression. Reconstruction of the CMD2 locus revealed a highly complex region with nearly identical gene sets but limited microsynteny between the two cultivars.
Conclusions
The genome maps of the CMD2 locus in both 60444 and TME3, together with the newly annotated genes, will help the identification of the causal genetic basis of CMD2 resistance to geminiviruses. Our de novo cassava genome assemblies will also facilitate genetic mapping approaches to narrow the large CMD2 region to a few candidate genes for better informed strategies to develop robust geminivirus resistance in susceptible cassava cultivars.

Abstract

Background
Cassava is an important food crop in tropical and sub-tropical regions worldwide. In Africa, cassava production is widely affected by cassava mosaic disease (CMD), which is caused by the African cassava mosaic geminivirus that is transmitted by whiteflies. Cassava breeders often use a single locus, CMD2, for introducing CMD resistance into susceptible cultivars. The CMD2 locus has been genetically mapped to a 10-Mbp region, but its organization and genes as well as their functions are unknown.
Results
We report haplotype-resolved de novo assemblies and annotations of the genomes for the African cassava cultivar TME (tropical Manihot esculenta), which is the origin of CMD2, and the CMD-susceptible cultivar 60444. The assemblies provide phased haplotype information for over 80% of the genomes. Haplotype comparison identified novel features previously hidden in collapsed and fragmented cassava genomes, including thousands of allelic variants, inter-haplotype diversity in coding regions, and patterns of diversification through allele-specific expression. Reconstruction of the CMD2 locus revealed a highly complex region with nearly identical gene sets but limited microsynteny between the two cultivars.
Conclusions
The genome maps of the CMD2 locus in both 60444 and TME3, together with the newly annotated genes, will help the identification of the causal genetic basis of CMD2 resistance to geminiviruses. Our de novo cassava genome assemblies will also facilitate genetic mapping approaches to narrow the large CMD2 region to a few candidate genes for better informed strategies to develop robust geminivirus resistance in susceptible cassava cultivars.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:04 Faculty of Medicine > Functional Genomics Center Zurich
07 Faculty of Science > Department of Plant and Microbial Biology
07 Faculty of Science > Zurich-Basel Plant Science Center
Dewey Decimal Classification:580 Plants (Botany)
Scopus Subject Areas:Life Sciences > Biotechnology
Life Sciences > Structural Biology
Life Sciences > Ecology, Evolution, Behavior and Systematics
Life Sciences > Physiology
Life Sciences > General Biochemistry, Genetics and Molecular Biology
Life Sciences > General Agricultural and Biological Sciences
Life Sciences > Plant Science
Life Sciences > Developmental Biology
Life Sciences > Cell Biology
Uncontrolled Keywords:Biotechnology, Plant Science, General Biochemistry, Genetics and Molecular Biology, Developmental Biology, Cell Biology, Physiology, Ecology, Evolution, Behavior and Systematics, Structural Biology, General Agricultural and Biological Sciences
Language:English
Date:1 December 2019
Deposited On:04 Feb 2020 12:59
Last Modified:22 Apr 2020 22:33
Publisher:BioMed Central
ISSN:1741-7007
OA Status:Gold
Free access at:PubMed ID. An embargo period may apply.
Publisher DOI:https://doi.org/10.1186/s12915-019-0697-6
PubMed ID:31533702
Project Information:
  • : FunderSNSF
  • : Grant IDIZLSZ3_149092
  • : Project TitleSAVUCA: Southern African Value Added Cassava: Next-generation cassava with enhanced agronomic and industrial performances for southern Africa

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