Extension of thein vivohaploid induction system from maize to wheat

Abstract

3Doubled haploid breeding technology has been one of the most important techniques for 1 4 accelerating crop breeding. In compare to in vivo haploid induction in maize, which is efficient 1 5 and background independent, wheat haploid production by interspecific hybridization pollinated 1 6 with maize is influenced by genetic background and requires rescue of young embryos. Here, we 1 7 analyzed the homologues of maize haploid induction gene MTL/ZmPLA1/NLD in several crop 1 8 species systematically, the homologues are highly conserved in sorghum, millet and wheat etc. 1 9Since wheat is a very important polyploidy crop, as a proof of concept, we demonstrated that the 2 0 in vivo haploid induction method could be extended from diploid maize to hexaploid wheat by 2 1 knocking out the wheat homologues (TaPLAs). Result showed that double knock-out mutation 2 2 could trigger wheat haploid induction at ~ 2%-3%, accompanied by 30% -60% seed setting rate. 3The performance of haploid wheat individual showed shorter plant, narrower leaves and male 2 4 sterile. Our results also revealed that knockout of TaPLA-A and TaPLA-D do not affect pollen 2 5 viability. This study not only confirmed the function of the induction gene and explored a new 2 6approach for haploid production in wheat, but also provided an example that the in vivo haploid 2 7 induction could be applied in more crop species with different ploidy levels. Furthermore, by 2 8 combining with gene editing, it would be a fast and powerful platform for traits improvement in 2 9 polyploidy crops breeding. 3 0