B × R cross de rived parental line development using breeding value: A new model for hybrid rice parental line development

Three-line hybrid rice system is the most successful and widely practiced method around the world. Hybrid rice breeders have used B × B, A × R and R × R (R = Restorer line, B = Maintainer line, A = CMS line) scheme of parental line improvement frequently and avoided B × R and R × B scheme. As a result, female parents lack the genetic diversity carried by R lines. But B × R and R × B mating have great potential to produce high value parental lines of hybrid rice and overcome the limitation of the previous approach. We have demonstrated a new method for three-line hybrid system to minimize the barrier of crossing in parent selection for developing new elite maintainers and restorers. Parental combinations were selected based on breeding value of the genotypes. Breeding values were estimated based on ancestor, pedigree information and yield data of 74 test genotype to select parents for restorer and maintainer line improvement. This new protocol allows (B × R), (R × B) (R × Elite) and (B × Elite) improvement technique to bring out high yielding diverse B and R lines. This B line will be used for developing new A line in the genetic background of B line. Doubled haploid and RGA i.e. rapid generation advance tools of breeding will save the precious time and reduce breeding cycle length; and large population size will increase selection accuracy. We have predicted the genetic gain in parental line development for four parental cross using the studied 74 genotypes for doubled haploid and rapid generation advance methods. Our objectives were to demonstrate the new breeding approach plus breeding value and positive dominant gene effect-based parent selection strategy. We are hopeful about the new method that hybrid rice breeders across the world will extract benefit utilizing the new methodology of hybrid rice parental line development.