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Weedy rice (Oryza spp.): what’s in a name?
- Nilda Roma-Burgos, Maggie Pui San Sudo, Kenneth M. Olsen, Isabel Werle, Beng-Kah Song
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- Journal:
- Weed Science / Volume 69 / Issue 5 / September 2021
- Published online by Cambridge University Press:
- 22 March 2021, pp. 505-513
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There are two species of cultivated rice in the world—Oryza sativa L. from Asia and Oryza glaberrima Steud. from Africa. The former was domesticated from the wild progenitor Oryza rufipogon Griff. and the latter from the African wild rice species Oryza barthii A. Shiv. The first known center of rice cultivation in China generated the O. sativa subspecies japonica. The indica subspecies arose from the second center of domestication in the Ganges River plains of India. Variants of domesticated lines and the continuous hybridization between cultivated varieties and the wild progenitor(s) resulted in weedy rice types. Some weedy types resemble the wild ancestor, but the majority of weedy rices today bear close resemblance to cultivated rice. Weedy rice accompanies rice culture and has increased in occurrence with the global shift in rice establishment from transplanting to direct-seeded or dry-drill-seeded rice. Weedy rice (Oryza spp.) is the most difficult weed to control in rice, causing as much as 90% yield loss or abandonment of severely infested fields. The gene flow continuum between cultivar and weedy rice or wild relative, crop de-domestication, and regionalized adaptation have resulted in a myriad of weedy rice types. The complex lineage of weedy rice has resulted in confusion of weedy rice nomenclature. Two names are generally used for weedy rice—Oryza sativa L. and Oryza sativa f. spontanea. Genomic data show that O. sativa L. applies to weedy rice populations derived from cultivated O. sativa, whereas O. sativa f. spontanea applies only to weedy types that primarily descended from O. rufipogon. Neither of these names applies to African weedy rice, which is of African wild rice or O. glaberrima lineage. Therefore, unless the lineage of the weedy population in question is known, the proper name to use is the generalized name Oryza spp.
Morphology of Malaysian Weedy Rice (Oryza sativa): Diversity, Origin and Implications for Weed Management
- Edi Sudianto, Ting-Xiang Neik, Sheh May Tam, Tse-Seng Chuah, Akmal Adilah Idris, Kenneth M. Olsen, Beng-Kah Song
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- Journal:
- Weed Science / Volume 64 / Issue 3 / September 2016
- Published online by Cambridge University Press:
- 20 January 2017, pp. 501-512
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Weedy rice is one of the most dominant and competitive weed species found throughout rice planting areas worldwide. In Malaysia, a combination of agricultural practices such as direct seeding and shared use of machinery has contributed to the rapid proliferation of weedy rice across paddy fields in recent decades. Here, we report on the morphological characterization of weedy rice populations and inferred origin(s) of different morphotypes present in Peninsular Malaysia. Eight weedy rice morphotypes were distinguished based on a combination of traits such as awn presence/absence and hull color, from 193 accessions collected in 17 locations. Results showed a high proportion of awnless accessions (strawhull-, intermediate strawhull-, and brownhull-colored morphotypes, together composing 65% of sampled accessions), with awned accessions represented by strawhull, brownhull, and blackhull forms. Clustering and PCA analyses revealed four major clusters: (1) O. rufipogon and the majority of awned, blackhull, and brownhull—suggestive of a type of weedy rice originating from wild Oryza populations; (2) elite indica cultivar rice and the majority of strawhull weeds—supporting a previous proposal that weedy rice from Malaysia mainly evolved from indirect selection on cultivars for easy-shattering feral forms; (3) the majority of brownhull; and (4) a mixture of other weedy morphotypes—potentially reflecting multiple origins and subsequent admixture. The combination of key morphological descriptors will be useful for advising farmers appropriately in strategies for controlling the spread of weedy rice, including periodic manual weeding to reduce buildup of the seed bank in the fields.