MYO, a Candidate Gene for Haploid Induction in Maize Causes Male Sterility

Doubled haploid technology is highly successful in maize breeding programs and is contingent on the ability of maize inducers to efficiently produce haploids. Knowledge of the genes involved in haploid induction is important for not only developing better maize inducers, but also to create inducers in other crops. The main quantitative trait loci involved in maize haploid induction areqhir1andqhir8. The gene underlyingqhir1has been discovered and validated by independent research groups. Prior to initiation of this study, the gene associated withqhir8had yet to be recognized. Therefore, this research focused on characterizing positional candidate genes underlyingqhir8. Pursuing this goal, a strong candidate forqhir8,GRMZM2G435294(MYO), was silenced by RNAi. Analysis of crosses with these heterozygous RNAi-transgenic lines for haploid induction rate revealed that the silencing ofMYOsignificantly enhanced haploid induction rate by an average of 0.6% in the presence ofqhir1. Recently,GRMZM2G465053(ZmDMP) was identified by map-based gene isolation and shown to be responsible forqhir8. While our results suggest thatMYOmay contribute to haploid induction rate, results were inconsistent and only showing minor increases in haploid induction rate compared toZmDMP. Instead, reciprocal crosses clearly revealed that the silencing ofMYOcauses male sterility.