Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: 2/24/2002
Publication Date: N/A
Technical Abstract: In the 2000 and 2001 rice planting seasons 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. This condition could provide a favorable environment for outcrossing between cultivated rice and red rice. Outcrossing was assessed based on four simple sequence repeat (SSR) molecular markers that were used to differentiate hybrids from rice cultivars and red rice. At maturity in 2000, approximately 12,000 "apparent" red rice seeds from combine-harvested plots of IMI rice cultivars, CF 2551, CF 0051, or CF 3291 (later flowering), and 13,000 seeds from red rice-like plants growing adjacent to CF 2551 or CF 0051 plots were selected. These seeds were planted in the greenhouse and the resulting seedlings were sprayed three times with 71 g/ha (0.063 lb/A) imazethapyr herbicide at 7 day intervals. Seventy one of fthe 12,000 apparent red rice seedlings and 78 of the 13,000 from red rice- like plants survived the three herbicide applications. DNA was extracted from survivors and fingerprinted using four SSR markers for rice to determine hybridization rates between cultivated rice and red rice. A maximum of three of the 149 survivors had banding patterns consistent with true hybridization indicating an average outcrossing rate of about 0.012%. Although, this number is very small, it may translate into hundreds of plants/ha depending on the level of red rice infestation.