|Estorninos Jr., Leopoldo|
Submitted to: North Central Weed Science Society US Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 12/12/2005
Publication Date: 12/15/2005
Citation: Gealy, D.R., Estorninos Jr., L., Wilson, C.E., Agrama, H. 2005. Confirmation of hybridization between rice and phenotypically distinct red rice types in Arkansas rice fields. North Central Weed Science Society US Proceedings. Dec. 12-15, 2005 Kansas City, MO, Vol. 60. Interpretive Summary:
Technical Abstract: This review details several key findings from red-rice rice outcrossing evaluations in research plots and in grower fields in Arkansas from 2000 to 2005. Observations from research plots, controlled crosses, and grower fields have provided us with several easily discernable phenotypic traits (e.g. leaf pubescence, stem and leaf coloration, days to flowering, awn length) that can be very useful in establishing the general biotype of the red rice parent involved in the original cross with rice. For instance blackhull awned red rice types crossed commercial long grain rice typically produce hybrids (first generation cross) with purple colored lower stems (basal leaf sheaths), and/or pink awns, and normal flowering patterns, while hybrids derived from strawhull awnless red rice types produce hybrids with normal green stems, no awns, and extremely delayed flowering periods. In combination with these and other phenotypic traits( e.g. seed pericarp color, seed shape, leaf pubescence, plant height, culm growth angle), SSR DNA fingerprinting and subsequent mathematical analyses can be used to infer population structure and the probable parentage of unknown crosses. Evaluation of reciprocal outcrossing between pairs of rice cultivars (both herbicide-resistant and non-resistant) and red rice biotypes, chosen for their overlapping flowering periods in order to optimize outcrossing, has revealed substantial year-to-year and cultivar-biotype variations at Stuttgart, AR. Outcrossing estimates (based on phenotypic traits only) have ranged from as high as 0.79% in 2005 in a Kaybonnet rice (female)/#8 awned blackhull red rice (male) to as low as 0.006% in 2001 in a StgS awnless strawhll red rice (female)/CL121 imidazolinone-resistant rice plot. The greatest outcrossing between imidazolinone-resistant rice and red rice was 0.54% in a CL161 rice (female)/#8 awned blackhull red rice (male) plot in 2004. Outcrossing was usually much greater when red rice, instead of cultivated rice, served as the pollen donor. In circumstances where red rice serves as the pollen donor in outcrossing, the hybrid seed will be removed from the field during harvest, thus minimizing the chance of contaminating the field for next year. However, the harvested rice may be of lower value if it is contaminated with red bran hybrid seed. Conversely, since red rice usually shatters prior to harvest, outcrosses with red rice as the female, may result in fields contaminated for future growing seasons.