High-Contiguity Haplotype-Resolved Genome Assembly of the Hexaploid Actinidia valvata Rootstock Sheds Light on Waterlogging Resistance Gene.
Lin M, Li Z, Deng CH, Li C, Zhang Z
Crop Improvement
Kiwifruit vines in waterlogged soils typically die within days — this rootstock survives, and the gene behind that toughness is now identified and editable for breeders trying to keep orchards alive through increasingly wet winters.
A kiwifruit relative called Actinidia valvata has an unusually complex genome — it carries six copies of its entire genetic blueprint instead of the usual two. Researchers mapped all six copies in detail and discovered that one particular gene, activated mainly in one of those copies, tells the plant how to cope when its roots are sitting in water. When they inserted extra copies of that gene into regular kiwifruit plants, those plants became significantly better at surviving floods.
Key Findings
The hexaploid genome contains 174 chromosomes across 6 haplotypes, with over 82% of chromosomes telomere-capped and three haplotypes achieving 100% telomeric representation — indicating exceptional assembly completeness.
Approximately 212,055 protein-coding genes were predicted (~35,000 per haplotype), with the subgenome structure traced to two ancestral donors: Actinidia polygama (contributing 2 sub-genomes) and Actinidia macrosperma (contributing 4 sub-genomes).
Overexpression of the B1 haplotype copy of an ethylene-response factor (ERF) gene in transgenic kiwifruit lines conferred enhanced waterlogging resistance, demonstrating subgenome-specific functional divergence.
chevron_right Technical Summary
Scientists assembled a complete, high-quality genome of a waterlogging-tolerant kiwifruit rootstock, revealing how its six-copy (hexaploid) genome is structured and identifying a specific gene that, when boosted, helps kiwifruit survive flooded conditions.
Abstract Preview
Polyploidisation, creating redundant or diverged copies of the genome, is a major driving force in plant evolution, diversification and environmental adaptation, including for the kiwifruit genus (...
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Kiwifruit, or Chinese gooseberry, is the edible berry of several species of woody vines in the genus Actinidia. The most common cultivar group of kiwifruit is oval, about the size of a large hen's egg: 5–8 centimetres in length and 4.5–5.5 cm in diameter. Kiwifruit has a thin, fuzzy, fibrous, lig...