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Haploid plants after doubling the chromosomes can give rise to diploid homozygote lines, which can be used as DH lines in breeding new varieties or as initial plant material in creating F1 hybrids. This work studied natural polyembryony and the effect of growth regulators on induction of polyembryonic seeds and haploid embryogenesis in five species of the genus Capsicum. Water solutions of the following growth regulators were used: 2,4-D (2,4-dichlorophenoxyacetic acid) and BNOA (beta-naphthoxyacetic acid) at 0.001% used separately or combined with BAP (benzylamino-purine). Twin seed frequency was highest in C. chinense and lowest in C. baccatum var. pendulum. In C. annuum the share of twin embryos was highest in the 'Corno di toro' variety; 2,4-D clearly increased the number of twin plants only in 'Corno di toro' seeds. Treatment with combinations of 2,4-D or BNOA with BAP increased the frequency of polyembryonie seeds in the 'ATZ1' line. In C. frutescens the frequency of polyembryony increased following application of BNOA with BAP. Of all the seeds tested, seven haploid plants were obtained, representing C. frutescens, C. chacoense and C. baccatum var. pendulum. The differences in the frequency of polyembryony in the studied genotypes points to genetic control of this phenomenon. The presence of monoploid plants definitely depends on the genotype, as a high frequency of polyembryony is not always accompanied by a high share of haploid plants. For most genotypes evaluated, the effect of growth regulators was disadvantageous, resulting in a considerable decrease in the share of twin plants among germinated seeds.
The effect of C17 and W14 induction media on the formation of embryo-like structures (ELS) from F3 generation of nine hexaploid oat hybrids was investigated in the study. In all genotypes, the highest number of ELS (0.6 - 12.1/100 anthers) was obtained on C17 medium. The efficiency of plant regeneration on medium 190-2 was tested, in relation to different ELS culture conditions. The highest rate of green plants per 100 ELS (3.3 - 42.4) was produced by incubation at 22oC in the dark for the first two weeks. Among 36 green regenerants, 28 (77.8%) were haploid and 8 (22.2%) were spontaneous doubled haploids, fully fertile. After colchicine treatment of haploid plants, 19 were partially fertile and set from 1 to 15 seed per panicle.
Anthers of twenty triticale genotypes were cultured on three different media: 1 - PII (Chuang et al. 1978) with increased 2,4-D to 2 mg L⁻¹ and agarose 6 g L⁻¹ , 2 - Macro-, micronutrients and vitamines like in MN6 (Chu, Hill 1988) + 2 mg L⁻¹ 2.4-D + 0.5 mg L⁻¹ KIN + 5 mg L⁻¹ FeEDTA + 90 g L⁻¹ sucrose; 3 - Macro-, micronutrients and vitamines like in MN6 (Chu, Hill, 1988) + 2 mg L⁻¹ 2.4-D + 0.5 mg L⁻¹ KIN + 5 mg L⁻¹ FeEDTA + 120 g L⁻¹ sucrose. Embryoid induction and plant regeneration were influenced by donor plant genotype and induction medium. Medium 1 was the best for embryoid induction, while for green plant regeneration the best were media 1 and 2. Out of 300 anthers from each genotype plated on each of the three media, 64-1250, 12-486 and 6-212 somatic embryos and 8-86, 3-136 and 1-26 green plants were recorded, on media 1, 2 and 3, respectively.
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Gene segregation in a barley DH population

72%
A large population of anther culture-derived barley regenerants and their progeny was tested for allele segregation at 1 isozyme and 8 morphological marker loci. The segregation of genetic markers was examined separately for haploid, diploid and polyploid regenerants. All the 9 analysed genes except al (albino lemma) on chromosome 3 segregated according to the expected 1:1 ratio in the microspore-derived barley population. There was no difference in allele distribution between haploid and diploid regenerants. Among the limited number of 34 analysed tetraploids a significant excess of the dominant allele at locus о (orange lemma) of chromosome 6 was also observed. The recombination frequency between linked genes (n - lk2 on chromosome 1 and r - s on chromosome 7) estimated in the DH population did not differ significantly from recombination rates calculated in F₂ progeny or presented in barley chromosome maps. The phenomenon of gametic selection is discussed in relation to the genotype dependency of anther culture response and procedures used for DH production in barley.
Haploid wheat plants have been produced by a new method of zygote rescue carried out after distant pollination. Wheat stigmas were pollinated with maize pollen and subsequently the activated egg cells from the elongated ovaries were rescued for in vitro plant development in single cell culture. As the control, 2-week-old embryos were also dissected and then cultured. The efficiency of both techniques was comparable. Wheat was also pollinated with rice, and the further development of rescued zygotes into multicellular structures is reported here for the first time. Because the lack of a normal endosperm hampers embryo development even in the early stages, early zygote rescue (two days after distant pollination) may represent a more efficient way of producing double haploid (DH) plants in cultivars that are recalcitrant in androgenic cultures, after further optimization of in vitro culture of isolated single cells.
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