Combining two semidwarfing genesd60andsd1for reduced height in ‘Minihikari’, a new rice germplasm in the ‘Koshihikari’ genetic background

Abstract

Dwarfing in rice has dramatically improved and stabilized rice yields worldwide, often controlled by a single dwarf gene, sd1. A novel semidwarf gene d60 complements the gametic lethal gene gal, such that the F(1) between 'Hokuriku 100' (genotype d60d60GalGal, Gal: mutant non-lethal allele) and 'Koshihikari' (D60D60galgal, D60: tall allele) would show 25% sterility due to deterioration of gametes bearing both gal and d60. The F(2) would segregate as one semidwarf (1 d60d60GalGal) : two tall and 25% sterile (2 D60d60Galgal) : six tall (2 D60d60GalGal : 1 D60D60GalGal : 2 D60D60Galgal : 1 D60D60galgal), skewed from a Mendelian segregation ratio of one semidwarf : three tall for a single recessive gene. To pyramid d60 and sd1, into the Japanese super-variety 'Koshihikari', the F(1) (D60d60Galgal) of 'Koshihikari' × 'Hokuriku 100' was first backcrossed with 'Koshihikari', and the BCF(1) segregated into a ratio of one tall and 25% sterile (D60d60Galgal) : two tall (1 D60D60Galgal : 1 D60D60galgal). Tall, 25% sterile BC(1)F(1) plants (D60d60Galgal) were then selected for pollen sterility and backcrossed with 'Koshihikari' as the recurrent parent. It is unnecessary to grow out and select a semidwarf from the BC(n)F(2) if a pollen parent with ~70% pollen fertility is chosen from the BC(n)F(1) to backcross with the recurrent parent. Semidwarfing genes d60 and sd1 were successfully pyramided into the 'Koshihikari' genome by crossing isogenic lines 'Koshihikari d60' and 'Koshihikari sd1', to produce 'Minihikari', a new parental source of both d60 and sd1. 'Minihikari' displayed super-short stature due to the combination of sd1 and d60, which are genetically and functionally independent.

The Gametic Non-Lethal Gene Gal on Chromosome 5 Is Indispensable for the Transmission of the Co-Induced Semidwarfing Gene d60 in Rice

“…However, in consideration of the maintenance and expansion of genetic diversity, this gene should not be solely relied upon for the development of semidwarf varieties. Through this study, we identified a new semidwarfing gene d60, which shows strong lodging-resistance, and genetically independence from sd1 [23]. Further research could elucidate the function of d60 and enable the development of novel semidwarf rice varieties.…”

“…To date, there is no evidence that the supposed semidwarf gene d60 is inherited as a single recessive gene according to the ratio of 1D60D60:2D60d60:1d60d60. However, double dwarfness due to a combination of d60 and sd1 was obtained via skewed segregation, and therefore d60 is regarded as an independent allele of sd1 [23].…”

Control of plant height by 24 alleles at 12 quantitative trait loci in rice

“…Previous reports indicated that genes can be pyramided to affect PH. Tomita (2012) showed that pyramiding two semidwarfing genes, d60 and sd1, resulted in a PH that was shorter than that using either d60 or sd1. Hu et al (2013) reported that a double mutant of tud1/d61 was shorter than either tud1 or d61, although tud1 and d61 were already two rice dwarf mutants.…”

Identification of Rice Large Grain Gene GW2 by Whole-Genome Sequencing of a Large Grain-Isogenic Line Integrated with Japonica Native Gene and Its Linkage Relationship with the Co-integrated Semidwarf Gene d60 on Chromosome 2

“…Then, we conducted whole-genome analysis of the developed large grain isogenic Koshihikari and identified a gene responsible for the large grain. Furthermore, we developed a large grain/semi-dwarf isogenic line by integrating both the identified large grain gene and the semidwarfing gene d60 [16].…”