Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/28/2002
Publication Date: 2/15/2002
Citation: Estorninos, L.E., Gealy, D.R., Dillon, T.L., Baldwin, F.L., Burgos, N.R., Tai, T. 2002. DETERMINATION OF HYBRIDIZATION BETWEEN RICE AND RED RICE USING MICROSATELLITE MARKERS. Proceedings of Southern Weed Science Society. 55:197.
Technical Abstract: Simultaneous flowering of cultivated rice and red rice creates a favorable environment for hybridization. Hybridization can be assessed based on molecular markers. Four simple sequence repeat (SSR) markers, previously found to discriminate hybrids from cultivated rice and red rice, were used to determine the rate of hybridization. In the 2000 rice planting season at Stuttgart, AR, two IMI herbicide resistant rice cultivars (CF 2551 and CF 0051) were found to flower nearly simultaneously with a strawhull red rice biotype. Red rice-infested IMI rice plots were combine harvested. From these samples, 12,000 apparent red rice seeds (medium grain) were selected by hand. At the same field site, 13,000 seeds were harvested directly from panicles on numerous red rice-like plants (tall with rough leaves) growing between IMI rice plots. All 25,000 seeds were planted in the greenhouse and seedlings were sprayed three times with 0.063 lb/A (0.07 kg/ha) imazethapyr herbicide at 7 day intervals. Sixty-nine of the 12,000 apparent red rice seeds and 78 of the 13,000 from red rice-like plants survived the three herbicide applications. DNA was extracted from survivors and fingerprinted. Only three of the 147 survivors had banding patterns consistent with true hybridization indicating an outcrossing rate of about 0.012%. Although this number is very small, it may translate into hundreds or thousands of plants per field depending on the level of red rice infestation. A field infested with red rice that had been planted with CF 2551 in 2000 was sprayed three times with imazethapyr herbicide in 2001. The initial red rice population density in 2001 was approximately 122 plants/ft2 (1310 plants/m2) in the 30,000 /ft2 plot area. Seven hundred twenty plants survived the three herbicide applications. DNA was extracted and fingerprinted from the initial 173 survivors. Seventeen percent of the 173 survivors had bands consistent with CF 2551 in all four SSR markers and about 51% had bands consistent with at least three of the four markers. About 5% of the 173 survivors produced banding patterns in all four markers that were consistent with true hybridization between CF 2551 and Stuttgart strawhull red rice, while 22% produced similarly consistent bands in at least three of the four markers. These survivors had generally pale, rough, and droopy leaves, and were very late to mature. These characteristics are consistent with those found in red rice hybrids observed previously. An outcrossing test was also done between a nonherbicide resistant rice and red rice. Starbonnet rice was found to flower almost simultaneously with Stuttgart blackhull red rice. About 2,500 seeds of Starbonnet from the year 2000 outcrossing pairs were planted in the greenhouse. DNA was extracted from 14-day-old seedlings and fingerprinted. None of the bands showed hybridization patterns consistent with Starbonnet and Stuttgart blackhull red rice.