FDo the six types of Sri Lanka’sOryza comprise a domesticated-weed-wild complex?
Asanka
Tennakoona,b,1, Salinda
Sandamalc,d,1, Song Gec,d, Arthur
Meloe, Yao Zhaof, Buddhi
Marambeg, Norman C. Ellstrandh,
Beng-Kah Songi,2, Disna
Ratnasekeraa,2
aDepartment
of Agricultural Biology, Faculty of Agriculture, University of Ruhuna,
81100, Matara, Sri Lanka; bDepartment of Biosystems
Technology, Faculty of Technology, Eastern University, 30350, Sri Lanka;cState Key Laboratory of Systematic and Evolutionary
Botany, Institute of Botany, Chinese Academy of Sciences, Beijing,
100093, China; dUniversity of Chinese Academy of
Sciences, Beijing, 100049, China; eInova Genética
LTDA, Santa Barbara Farm, BR 251, Km18, Cristalina, Goiás, Brazil;fJiangxi Province Key Laboratory of Watershed
Ecosystem Change and Biodiversity, Center for Watershed Ecology,
Institute of Life Science and School of Life Sciences, Nanchang
University, Nanchang, 330031, China; gDepartment of
Crop Science, Faculty of Agriculture, University of Peradeniya, Kandy,
20400, Sri Lanka; hDepartment of Botany and Plant
Sciences, University of California, Riverside, CA, USA;iSchool of Science, Monash University Malaysia, 46150,
Bandar Sunway, Selangor, Malaysia
1should be considered joint first author.
2should be considered joint corresponding author.
Corresponding author email:disnaratnasekera@gmail.com
Corresponding author address: Department of Agricultural
Biology, Faculty of Agriculture, University of Ruhuna, 81100, Matara,
Sri Lanka
Abstract
Genetic studies of Domesticated-Weed-Wild Complexes (DWWC) have
typically focused on one-way introgression of crop alleles into wild or
weedy populations, with little consideration of the entire natural
ecosystem. In Sri Lanka, DWWC is diverse, comprising six evolutionarily
discrete groups in the genus Oryza . Using 33 neutral simple
sequence repeat (SSR) loci, we characterized six Oryza groups to
understand the genetic background and evolution of DWWC components. Our
analysis found that Oryza groups have large population sizes and
high inter-group long-term gene flows. Asymmetric gene flows were found
between wild and weedy rice groups, but the rare alleles shared among
DWWC components provide additional evidence for extensive and enduring
exchange, highlighting the dynamic nature of this complex genetic
admixture among different Oryza lineages. We found high genetic
diversity at the population and species levels due to mixed DWWC
components over the generations. Weedy rice types exhibit genetic
incorporation through admixture from both crop and wild species,
highlighting the multi-way genetic transfer in the evolution of weedy
rice types. Our findings support the idea that the DWWC is an integrated
complex in the Sri Lankan rice ecosystem and that its weedy rice has
multiple origins, including de-domestication via feralization of
cultivated rice, inter-varietal hybridization among distinct cultivated
rice types, adaptation, and invasion of rice cultivation areas by wildOryza species, and hybridization events between crop and wild
rice populations. Abandoned rice domesticates can also evolve into weedy
forms with less intimate human relationships and contaminate the rice
ecosystem.
Keywords: Domesticated-weed-wild complexes, Origin and
evolution, Oryza spp., Weedy rice