Submitted to: Arkansas Agricultural Experiment Station Research Series
Publication Type: Experiment Station
Publication Acceptance Date: 9/27/2005
Publication Date: 8/8/2005
Citation: Shivrain, V.K., Burgos, N.R., Sales, M.A., Gealy, D.R. 2005. Planting time and cultivar effects on outcrossing in Clearfield(tm) rice. In: Norman, R.L., Meullenet, J.-F., Moldenhauer, K.A.K., editors. B.R. Wells Rice Research Studies 2004, Arkansas Agricultural Experiment Station Research Series 529. p, 240-249. Available: http://www.uark.edu/depts/agripub/Publications/researchseries/. Interpretive Summary:
Technical Abstract: Experiments were conducted at the Rice Research and Extension Center (RREC), Stuttgart, Ark., from 2002 to 2004 to determine the effect of planting date on the synchronization of flowering between ClearfieldTM cultivars, ‘CL121’ and ‘CL161’, and Stuttgart strawhull red rice. Seeds were drill-planted in 10-ft long, 3-row plots starting from mid-April to the third week of May at weekly intervals. Each Clearfield cultivar was replicated four times at each planting date. Data on flowering were collected twice a week. At maturity, plant height was measured and seed samples were collected for planting and subsequent screening of hybrids. Plots were sprayed with Newpath® (0.063 lb ai/acre) in the following year to observe the number of hybrids resulting from the shattering of red rice in the preceding year. Seed samples collected were planted and sprayed with Newpath (0.063 lb ai/acre) at the Vegetable Substation, Kibler, Ark., in 2004 to observe the number of hybrids. Red rice, CL121, and CL161 planted in mid-April (first planting) started flowering 90, 95, and 97 days after planting (DAP), respectively. In the second planting, flowering started 85, 90 and 95 DAP for red rice, CL121, and CL161, respectively. In subsequent plantings, flowering time decreased by 5 to 7 days for the Clearfield cultivars as well as for the red rice. Synchronization in flowering was highest between CL121 and red rice compared to CL161 and red rice in all planting timings. Survivors of screening from seedlings were confirmed as hybrids by DNA fingerprinting with the single sequence repeat (SSR) primer RM 180. The six planting dates in 2003 produced 48, 8, 25, 18, 8, and 9 hybrids, respectively, for both cultivars. The highest synchronization in flowering between red rice and Clearfield rice at first planting produced the highest number of survivors. Despite less synchronous flowering, CL161 produced a higher number of hybrids with red rice than did CL121.