Nitrous Oxide‐Induced Chromosome Doubling of Maize Haploids

Abstract

Doubled haploid (DH) production is an important step in varietal development in maize (Zea mays L.), and the success rate of chromosome doubling determines a major portion of the production costs per DH line. Colchicine, the standard chemical used for chromosome doubling, is highly toxic and requires special disposal. In comparison, nitrous oxide (N2O) is a relatively safe gas with simple disposal requirements. Therefore, the objective of this study was to compare chromosome doubling treatment of maize seedlings with N2O with the standard colchicine treatment and a recently proposed alternative herbicide treatment containing amiprophos‐methyl and pronamide in two environments suitable for DH production (DH nursery and greenhouse). Various treatment factors, including different pressures and concentrations of N2O, O2, and air in the treatment chamber, imbibition duration, and treatment duration were analyzed for their effect on survival rate of germinated seedlings, reproduction rate measured as the proportion of haploid (D0) plants with seed set, and overall success rate (OSR) measured as the proportion of D0 plants with seed set obtained from the germinated seedlings. The OSR of the best N2O treatment ranged from 6.4 to 33.3%, whereas the OSR of colchicine ranged from 5.0 to 28.1%, depending on the year and environment. Nitrous oxide treatment did not have a significantly different OSR than herbicide treatment. In conclusion, N2O treatment is a competitive alternative to colchicine and herbicide treatments for chromosome doubling and offers safety and disposal‐related benefits.