Identification of maize-derived dominant gametophyte factors

Abstract

The use of gametophyte factors to protect specialty-type maize has long been advocated, but as of yet, they have made very little impact on preventing pollen contamination due to the complications associated with breeding with these materials, mainly the additive nature of the alleles. A dominant gametophyte factor (DGF) overcomes this problem, allowing for less time consuming production of gametophytic hybrids, but effectively utilized sources do not exist. Tcb1-s, a known DGF, is a teosinte introgression into maize and the leading candidate for utilization, however, it has several issues that limit its effective use in expediting the breeding process for gametophytic hybrids. The use of maize for a source of DGFs may overcome this problem; with the idea years of selection by farmers would likely have minimized any segregation for yield associated with these alleles, making their use for production of gametophytic hybrids an appealing option for modern breeders. Through screening and backcrossing selected maize accessions, we identified DGFs in seven accessions from race Maiz Dulce, which we document here as a starting point for identification of additional maize-derived DGFs. These accessions did not appear to segregate for yield, a marked improvement over existing DGFs. Additionally, we assessed the compatibility of identified maize-derived DGFs from one accession, and showed that, while lines are generally compatible, they are not obligately so since a single accession may segregate for multiple gametophyte factors. There is, therefore, a need to consider the compatibility of pairs of DGFs early in the inbreeding process. Maize-derived DGFs provide a more effective method of producing gametophytic hybrids, making their production economical enough to be brought to market. The use of DGFs has wider potential to benefit any producers interested in preventing pollen contamination with gametophytic hybrids through the same benefits provided to breeders for organic and other specialty systems. In combination with Ga1-m resistance, maize-derived DGFs provide a long-term gametophytic solution to pollen contamination, in a more expeditious way.