By Dr. Xiangqian Zhao
Scientist, Population Improvement
Plant Breeding, Genetics, and Biotechnology Division
11 September 2014, Thursday
Recurrent selection (RS) is commonly used in open-pollinated species and is gaining popularity in self-pollinated crops such as wheat, barley, and rice in some countries. At IRRI, RS officially started again in May 2012 to develop high-yielding pre-breeding lines by combining desirable alleles from multiple sources. Base populations for yield potential and specific traits were developed using 26 parents through manual crossing in the 2012WS; two selection cycles have been completed. Huge genetic variations for yield-related traits such as lodging resistance, stem and panicle size, and grain quality were created, which allows outstanding families and/or individuals being selected for variety development. Two cycles of RS in a bi-parental population increased average yield by 1.24% and 1.78% per year in the DS and WS, respectively. About 500 lines from the recurrent selection project have been chosen by different variety development breeders for further testing in India, Bangladesh, Myanmar, Pakistan, and Burundi. Twenty of the 200 lines tested in the 2014DS irrigated OYTs were among the top 50 high yielders of all 1,500 entries, and 57 entries are being tested in the 2014WS PYTs. Many of these lines have very low chalkiness (<3%) as well. It is clear that recurrent selection is very effective in improving quantitative traits in rice. In addition, a male sterile gene in msIR36 was fine-mapped and transferred into 70 elite breeding lines using marker-assisted backcrossing (MABC). This will greatly improve the efficiency of RS in the future. How to integrate RS with pedigree breeding and genomic selection will also be discussed.