Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 2/27/2012
Publication Date: 2/1/2013
Citation: Huang, B., Yan, Z., Deren, C.W., Yan, W., Mcclung, A.M. 2013. Evaluation of sterility and fertility of male sterile lines in the USPB farm. Rice Technical Working Group Meeting Proceedings. Feb.27-Mar.1,2012. Hot Springs, AR. pg. 69. Interpretive Summary:
Technical Abstract: Hybrid rice has proven to have a yield advantage of 15–20% over the best inbred cultivars at the commercial scale worldwide. At present, two methods have been successfully commercialized; the three-line and two-line systems. The three-line system consists of the male sterile (MS), maintainer and restoring lines. The two-line system has only the MS and restoring lines because sterility and fertility shifts in the MS line as a result of environmental changes. The two-line system has advantages over the three-line system by 1) simplifying seed production of both the hybrid and the MS line itself, and 2) opportunities for improving the level of heterosis are greater because the selection pool for identifying restorer lines is expanded. In the two-line system, male sterility and fertility of MS line are controlled by environmental factors such as temperature, day-length, or both. MS lines are male sterile when they head under conditions where the average day temperature >23 ºC and become male fertile when they head when the average day temperature is between 23 ºC and 13 ºC. Therefore, seed production of hybrids can be conducted in the summer and reproduction of MS line can be done in the autumn under southern US conditions. A good MS line should be completely male sterile in the summer and highly male fertile in the autumn. We tested six MS lines selected from our breeding program for a shift between male sterility and fertility at the University of Arkansas at Pine Bluff (UAPB) farm in 2011. The experimental lines were planted 9 times, a week apart for continuous heading from Aug. 13 to Oct. 8, 2011. Ten panicles of each line at each planting date were bagged as soon as heading occurred to prevent cross pollination from other sources. The seed setting rates of the bagged panicles were recorded. The seed set rates were zero for all lines which headed between Aug. 13 and Sep. 4. Average seed set rates over the six lines were 1.73, 5.9, 25.7, 20.6 and 17.9% when heading occurred on Sep. 10, 17 and 24, Oct. 1 and 8, respectively. The best line had a seed set rate of 53.6 and 48.8% when heading occured on Sep. 24 and Oct. 1, respectively. The 2nd best line had a seed set rate of 46.2 and 27.4% when they headed on Sep. 24 and Oct. 1, respectively. These results suggest that 1) there is genetic diversity for lines that respond to environmental changes causing a shift in pollen viability that can be used for hybrid breeding, 2) seed production of hybrids is effective when heading occurs within August, and 3) reproduction of the MS line is best when heading occurs after mid-September. The UAPB farm is an ideal place for breeding two-line hybrid rice because it is isolated from commercial rice production fields.