Low relative humidity increases haploid production in durum wheat x maize crosses

Haploidization is a useful tool for genetic analysis and plant breeding, but a consistent and satisfactory protocol for haploid production has been difficult to achieve in durum wheat. The objective of this study was to analyze the influence of the relative humidity of the environment, when culturing detached tillers during the production of haploids plants in durum wheat by the maize method. Thirty-eight F-3 lines from eight crosses of durum wheat were pollinated with bulked pollen from three commercial maize hybrids. A mixture of 2-4D and dicamba was used as a hormone treatment. The numbers of caryopses, embryos and haploids plants were scored. When 65-85% (light-dark) humidity was substituted for 55-65% the number of haploids per spike increased notably. This increased frequency was largely attributed to a rise in the production of generated caryopses. On average, 15.2 vs. 9.3 caryopses, 5.0 vs. 2.8 embryos, and 3.1 vs. 0.6 haploid plants, per spike, were produced under low and high humidity regimes, respectively.