Weedy red rice is conspecific weed of rice, identified as a threat to global rice production. As weedy rice is more tolerant to stresses than cultivated rice and has wide genetic and morphological variation we hypothesized that weedy rice has high herbicide tolerance and weed suppressive potential. Herbicide tolerance and weed suppressive potential of 54 weedy rice accessions were evaluated and the traits were associated with molecular markers. Accessions B2, B20 and S11 showed high tolerance to glyphosate and B49, B51 and S59 had high tolerance to flumioxazin. All the accessions were controlled 100% with 1311g a.i/ha (1.5x) rate of glufosinate. Accession B2 inhibited the growth of barnyardgrass and amazon sprangletop by more than 50% indicating its high weed suppressive potential. Nei’s gene diversity and Shannon’s information index among the weedy rice accessions were found to be 0.45 and 0.66 respectively indicating high genetic diversity among weedy rice accessions.

Weedy rice is of the same species as cultivated rice, Oryza, and is a common rice weed exhibiting allopathic characteristics. Incorporation of allelopathic traits from weedy rice into cultivated rice may have a positive impact on rice yield. The overall objective of this study was to characterize weedy rice accessions based on the allelopathic potential to suppress barnyardgrass. These accessions, once discovered, may be used in identifying phenotypic traits and genes associated with their weed suppressive trait. Ten weedy rice accessions, and five rice cultivars (Rex, CL163,Rondo, PI312777, PI338046) were screened using a stair-step technique. The allelopathic potential was calculated based on the percent inhibition of barnyardgrass. The best performing accessions were phenotyped for root characteristics in a lab setting. Lastly, 30 SSR markers were used to evaluate the weedy rice to identify markers associated with the trait. Accessions identified in this study should be considered in the development of weed-suppressive rice cultivars.