Production of doubled haploids in sugar beet (Beta vulgaris): an efficient method by a multivariate experiment

The present paper describes a detailed study of a highly efficient protocol to multiply the number of haploids in sugar beet production and subsequent chromosome doubling. The protocol involves an experiment investigating factorial interactions between cold pretreatment, seven genotypes of sugar beet, and kinetin to improve haploid embryo induction. In addition, the effects of color of ovules and flower bud position on haploid embryo induction were investigated. After subjecting the data to analysis of variance or Student's t test (P < .05), the effect sizes of the independent variables were also estimated. Cold pretreatment was effective in stimulating the ovules. The haploid embryo induction rate for 1-week cold pretreated ovules (9.01%) was higher than that of freshly cultured ones (6.15%). In comparison with hormone-free medium (5.16%), the gynogenesis rate for the media supplemented with 0.05 or 0.5 mg L-l kinetin increased to 7.58 and 10.05%, respectively. The genotype responses were significantly different. Interactions of kinetin x cold pretreatment, genotype x hormonal treatment, genotype x cold pretreatment, and the three-way interaction were statistically significant. Moreover, the main effects of flower bud position, ovule color, and comma-form ovule on gynogenic response were significant. After investigating the effect of 5 g L-l colchicine for 3, 5, or 7 min on one genotype's (SG2) specimens, all the haploid plantlets from the other genotypes were treated for 5 min as the best treatment. The paper discusses interactions of the factors, which may be interesting for others aiming to breed doubled haploid sugar beet or possibly other related plant species.