Development of Hybrid Rice in Louisiana.

Rice heterosis was first reported in the United States in 1926; nonetheless, successful commercialization of hybrid rice didn’t occur until early 1970s when Chinese scientists discovered the cytoplasmic male sterility from a biotype of wild species Oryza rufipogon. Through the use of Chinese germplasm, RiceTec successfully commercialized hybrid rice production in the southern U.S. in 1999. In 2011, RiceTec hybrid rice accounted for over 30% of the southern U.S. rice acreage. By incorporating the important hybrid rice sterility and fertility traits from introduced hybrid rice germplasm into elite U.S. genotypes, or even direct test-crossing between introduced male sterile lines and Louisiana cultivars or lines, we hope to be able to develop adapted hybrids with competitive yield, comparable milling, and acceptable grain quality in the near future. Breeding objectives include 1) creating and/or identifying male sterile (Cytoplasmic A or environmental sensitive S) lines and restorer (R) lines adapted to the Louisiana and southern U.S. environmental conditions, 2) development of elite cross combinations (hybrid varieties) through extensive test-crossing and yield trials, and 3) development of an effective and economical hybrid seed production technology for Louisiana by modifying or perfecting available technologies.

During last two years, research has been focused on the development of adapted male-sterile, maintainer, and restorer lines; production of large number of test crosses between introduced male sterile lines and elite Louisiana long-grain genotypes; observational trial of 700 test crosses; multi-location hybrid yield trial; and both mini- and small-scale concept hybrid seed production. Breeding populations have been significantly increased and rapidly advanced for the development of adapted male sterile, maintainer, and restorer lines by the extensive use of both greenhouse and Puerto Rico winter nursery. About 3,000 progeny rows ranging from F₃ to F₅ were grown in summer 2011 for various line developments. From observational test crosses trial, we have identified and harvested 118 cross combinations, which include 45 3-line and 73 2-line hybrids, for further milling and cereal chemistry evaluation. A total of 31 southern long-grain varieties/lines were found to have either partial or full restoring ability to CMS male sterile lines. A number of test crosses showed good agronomic characteristics and were chosen for re-evaluation in 2012. In the multi-location advanced hybrid yield trial, Two medium-grain hybrids LAH10 and LAH20 that were developed at Louisiana State University AgCenter’s Rice Research Station from introduced hybrid lines, along with two experimental long-grain hybrids 10TC447 and 10TC151 demonstrated good yield potential as compared with pureline cultivars CL151 and Caffey. Meanwhile, LAH10 was also tested and shown excellent yield potential in several other trials that included uniform regional rice nursery, Louisiana commercial advanced yield trial, date of planting, and variety x nitrogen trials. To facilitate future research needs, several different mini- and small-scale seed production methods were also proposed and tested.