Populations of doubled haploids for genetic mapping in hexaploid winter triticale.

To create a framework for genetic dissection of hexaploid triticale, six populations of doubled haploid (DH) lines were developed from pairwise hybrids of high-yielding winter triticale cultivars. The six populations comprise between 97 and 231 genotyped DH lines each, totaling 957 DH lines. A consensus genetic map spans 4593.9 cM is composed of 1576 unique DArT markers. The maps reveal several structural rearrangements in triticale genomes. In preliminary tests of the populations and maps, markers specific to wheat segments of the engineered rye chromosome 1R (RM1B) were identified. Example QTL mapping of days to heading in cv. Krakowiak revealed loci on chromosomes 2BL and 2R responsible for extended vernalization requirement, and candidate genes were identified. The material is available to all parties interested in triticale genetics.

The Ph1 locus of wheat does not discriminate between identical and non-identical homologues in rye.

The main locus responsible for diploid-like behavior of polyploid wheat in meiosis, Ph1, is located on the long arm of chromosome 5B (5BL). It restricts metaphase I pairing to essentially identical homologues. Introduction of 5BL into outcrossing autotetraploid rye severely reduced multivalent formation and increased the frequency of bivalents and univalents, but the key by which homologues were selected for effective pairing was not clear. We created doubled haploids of autotetraploid rye with the long arm of wheat 5BL, verified their nature by DNA markers, and analyzed metaphase I chromosome pairing. The doubled haploid nature guaranteed the presence of pairs of identical and non-identical homologues in each homologous group. The metaphase I pairing patterns were essentially the same as in plants from open pollination, with frequent bivalents and univalents and rare multivalents. The level of pairing was low and depended on the dosage of 5BL. The pairing levels show that unlike in wheat, in rye the Ph1 locus does not use homologue similarity as the criterion in selection of pairing partners. It is possible that the Ph1 of wheat and the rye chromosome pairing system are mutually exclusive. The minimum level of chromosome differences required for effective pairing in rye may be well above the maximum difference level tolerated by the Ph1 system of wheat. In other words, effective chromosome pairing in rye may be possible between non-identical chromosomes that might not normally pair in the Ph1 wheat background.

Androgenic response to preculture stress in microspore cultures of barley.

Various stresses such as starvation and cold or heat shocks have been identified as triggers in the induction of the microspore embryogenesis. This study attempts to quantify the effects of different pretreatment conditions for successful microspore culture of malting barley (cv. Scarlett). While the sporophytic microspore development could be induced from treated and nontreated microspores, abiotic stress was essential for embryo formation and plant regeneration. The type of stress treatment applied affected the numbers and the ratios of albino and green plants regenerated, as well as their fertility. The highest number of green plants was obtained after the treatment of anthers in 0.3 M mannitol at 32 degrees C for 24 h before microspore culture.

Direct embryogenesis and green plant regeneration from isolated microspores of hexaploid triticale (x Triticosecale Wittmack) cv. Bogo.

The use of doubled haploids improves the efficiency of cultivar development in many crops and can be helpful in genetic and molecular studies. The major problem with this approach is the low efficiency of green plant regeneration. We describe here an efficient method for inducing embryos and regenerating green plants directly from isolated microspores of hexaploid triticale (x Triticosecale Wittmack) cv. Bogo. The absence of growth regulators in the induction medium was the most effective condition for the formation of embryo-like structures. The highest induction rates were observed at microspore densities of 1.5x10(5) microspores and 2x10(5) microspores per milliliter. Such cultures produced an average of 54.9 green plants per single donor spike. The frequency of albino plants ranged from 9.3% to 22.9%. Among the green progeny tested, 30.8% were spontaneously doubled haploids.