Weedy rice (Oryza sativa f. spontanea) complexes on direct seeded rice (DSR) and its management strategy: A review

Weedy rice (Oryza sativa f. spontanea) is one of the most notorious weeds occurring in rice growing areas especially in direct-seeded rice (DSR) system, worldwide and the problem is pervasive. It is a complex of Oryza morphotypes widely distributed in the commercial rice fields in more than 50 countries of Asia, Africa, Latin America and Southeast Asia. Weedy rice is progenies of crosses between wild rice and cultivated. The major characteristic of weedy rice is easy shattering. Other characteristics observed are taller plants, fewer tillers, grains having awns and high percentage of red rice in milled rice. It is difficult to manage the infestation of weedy rice because of its morphological similarities with cultivated rice. Recently, biotechnology approach using genetically modified herbicide tolerant rice varieties may be an efficient strategy. A non-transgenic rice variety Clearfield’ is tolerant to Imidazolinone herbicides. It aims at determining whether the integration of Imidazolinone herbicides and tolerant trait in the genotypes can be used for controlling weedy rice in rice field. Satisfactory control of weedy rice requires an integrated approach based on the combination of preventive, cultural, mechanical, chemical and biotechnological means rather than using only a single method for its control.