Registration of two Oryza sativa tropical japonica germplasm lines selected for panicle architecture and grain size traits

Authors: Eizenga, Georgia; McClung, Anna; Huggins, Trevis

Submitted to: Journal of Plant Registrations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/10/2021
Publication Date: 7/31/2021
Citation: Eizenga, G.C., McClung, A.M., Huggins, T.D. 2021. Registration of two Oryza sativa tropical japonica germplasm lines selected for panicle architecture and grain size traits. Journal of Plant Registrations. https://doi.org/10.1002/plr2.20145.
DOI: https://doi.org/10.1002/plr2.20145

Interpretive Summary: In order to feed the world’s growing population, there is a need to increase rice yield since it is a staple food for half the world’s population. Increasing the number of branches and the number of seeds produced on the rice panicle (seed head) is a means of accomplishing this. The majority of the rice grown in the United States is from the Japonica rice subspecies which is difficult to cross with the other major subspecies, Indica, because of sterility problems. Having rice germplasm available in the Japonica genetic background that possesses greater panicle branching and higher seed production will help U.S. rice breeders develop new cultivars with higher yield. Two Japonica germplasm lines, SC14_166 and SC14_072, are being made available for breeding that can be used for improving medium grain and long grain market classes of rice. The SC14_072 long grain germplasm line has at least two major genes associated with increased grain length that is a highly desired grain appearance trait in the long grain market. The SC14_166 medium grain germplasm line possesses genes which increase the number of seed produced on the panicle. As part of this effort, DNA markers were developed which are linked to these desired traits and will facilitate breeding efforts to improve yield and grain size in tropical japonica-based breeding programs.

Technical Abstract: Two Estrela × NSFTV199 tropical japonica rice (Oryza sativa L.) germplasm lines designated as SC14_166 and SC14_072 contain alleles for improving panicle branching, seeds per panicle and grain length in tropical japonica rice and are being released by the USDA-ARS. Based on significant associations between SNP markers and targeted traits, SC14_166 contains alleles for two major genes, SPIKELET NUMBER (SPIKE) on chromosome (chr.) 4 (31.21 Mb) and FRIZZY PANICLE (FZP) on chr. 7 (28.29 Mb) which increase the number of panicle branches, seeds and spikelets per panicle. Based on associations with grain length, SC14_072 contains alleles for two major genes on chr. 3, GRAIN SIZE3 (GS3) at 16.73 Mb and GRAIN LENGTH3.2 (GL3.2) at 17.34 Mb resulting in an extra long grain. Both germplasm lines are recombinant inbred lines selected from the Estrela × NSFTV199 mapping population which segregated for panicle branching, number of seeds and spikelets per panicle, and grain length and width. SC14_166 is a medium grain with low amylose content and high gelatinization temperature. The plant is glabrous, flowers in about 70 days and is about 126 cm tall. The panicles have a mean of 12.6 primary branches and 115.6 seeds per panicle. SC14_072 is a long grain with a mean kernel length of 7.91 mm, that has low amylose content and high gelatinization temperature. The plant is pubescent, has the Pi-z blast resistance allele, flowers in about 74 days and is about 119 cm tall. These germplasm lines are well adapted to growing conditions in the southern USA and will benefit long grain and medium grain breeding programs that desire to increase grain dimensions and panicle architecture traits. Because they are derived from the tropical japonica subpopulation, like most cultivars in the USA, it is expected that they will be highly compatible for making breeding crosses and will contribute novel alleles to the gene pool.