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.

Quantitative trait loci and candidate genes associated with freezing tolerance of winter triticale (× Triticosecale Wittmack).

Freezing tolerance of triticale is a major trait contributing to its winter hardiness. The identification of genomic regions - quantitative trait loci (QTL) and molecular markers associated with freezing tolerance in winter hexaploid triticale - was the aim of this study. For that purpose, a new genetic linkage map was developed for the population of 92 doubled haploid lines derived from 'Hewo' × 'Magnat' F1 hybrid. Those lines, together with parents were subjected to freezing tolerance test three times during two winter seasons. Plants were grown and cold-hardened under natural fall/winter conditions and then subjected to freezing in controlled conditions. Freezing tolerance was assessed as the plants recovery (REC), the electrolyte leakage (EL) from leaves and chlorophyll fluorescence parameters (JIP) after freezing. Three consistent QTL for several fluorescence parameters, electrolyte leakage, and the percentage of the survived plants were identified with composite interval mapping (CIM) and single marker analysis (SMA). The first locus Qfr.hm-7A.1 explained 9% of variation of both electrolyte leakage and plants recovery after freezing. Two QTL explaining up to 12% of variation in plants recovery and shared by selected chlorophyll fluorescence parameters were found on 4R and 5R chromosomes. Finally, main locus Qchl.hm-5A.1 was detected for chlorophyll fluorescence parameters that explained up to 19.6% of phenotypic variation. The co-located QTL on chromosomes 7A.1, 4R and 5R, clearly indicated physiological and genetic relationship of the plant survival after freezing with the ability to maintain optimal photochemical activity of the photosystem II and preservation of the cell membranes integrity. The genes located in silico within the identified QTL include those encoding BTR1-like protein, transmembrane helix proteins like potassium channel, and phosphoric ester hydrolase involved in response to osmotic stress as well as proteins involved in the regulation of the gene expression, chloroplast RNA processing, and pyrimidine salvage pathway. Additionally, our results confirm that the JIP test is a valuable tool to evaluate freezing tolerance of triticale under unstable winter environments.

Genetic map of triticale compiling DArT, SSR, and AFLP markers.

A set of 90 doubled haploid (DH) lines derived from F(1) plants that originated from a cross between × Triticosecale Wittm. 'Saka3006' and ×Triticosecale Wittm. 'Modus', via wide crossing with maize, were used to create a genetic linkage map of triticale. The map has 21 linkage groups assigned to the A, B, and R genomes including 155 simple sequence repeat (SSR), 1385 diversity array technology (DArT), and 28 amplified fragment length polymorphism (AFLP) markers covering 2397 cM with a mean distance between two markers of 4.1 cM. Comparative analysis with wheat consensus maps revealed that triticale chromosomes of the A and B genomes were represented by 15 chromosomes, including combinations of 2AS.2AL#, 2AL#2BL, 6AS.6AL#, and 2BS.6AL# instead of 2A, 2B, and 6A. In respect to published maps of rye, substantial rearrangements were found also for chromosomes 1R, 2R, and 3R of the rye genome. Chromosomes 1R and 2R were truncated and the latter was linked with 3R. A nonhomogeneous distribution of markers across the triticale genome was observed with evident bias (48%) towards the rye genome. This genetic map may serve as a reference linkage map of triticale for efficient studies of structural rearrangements, gene mapping, and marker-assisted selection.

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.

Quantitative trait loci for leaf chlorophyll fluorescence parameters, chlorophyll and carotenoid contents in relation to biomass and yield in bread wheat and their chromosome deletion bin assignments.

Relatively little is known of the genetic control of chlorophyll fluorescence (CF) and pigment traits important in determining efficiency of photosynthesis in wheat and its association with biomass productivity. A doubled haploid population of 94 lines from the wheat cross Chinese Spring × SQ1 was trialled under optimum glasshouse conditions for 4 years to identify quantitative trait loci (QTL) for CF traits including, for the first time in wheat, JIP-test parameters per excited cross section (CSm): ABS/CSm, DIo/CSm, TRo/CSm, RC/CSm and ETo/CSm, key parameters determining efficiency of the photosynthetic apparatus, as well as chlorophyll and carotenoid contents to establish associations with biomass and grain yield. The existing genetic map was extended to 920 loci by adding Diversity Arrays Technology markers. Markers and selected genes for photosynthetic light reactions, pigment metabolism and biomass accumulation were located to chromosome deletion bins. Across all CF traits and years, 116 QTL for CF were located on all chromosomes except 7B, and 39 QTL were identified for pigments on the majority of chromosomes, excluding 1A, 2A, 4A, 3B, 5B, 1D, 2D, 5D, 6D and 7D. Thirty QTL for plant productivity traits were mapped on chromosomes 3A, 5A, 6A, 7A, 1B, 2B, 4B, 6B, 7B, 3D and 4D. A region on chromosome 6B was identified where 14 QTL for CF parameters coincided with QTL for chlorophyll content and grain weight per ear. Thirty-five QTL regions were coincident with candidate genes. The environment was shown to dominate in determining expression of genes for those traits.

Identification of wild and cultivated sunflower for breeding purposes by AFLP markers.

Amplified fragment length polymorphisms (AFLPs) represent one of the most powerful polymerase chain reaction (PCR)-based markers which enables one to discriminate single plants by DNA analysis. To date this technique has only been applied in cultivated sunflower to detect genetic diversity among oilseed inbred lines. In this article we report the use of AFLP markers to investigate the level of diversity within and between populations of Helianthus argophyllus collected in the Maputo area, Mozambique, both for taxonomic and breeding purposes. Three primer combinations gave the best results with 92 polymorphic fragments and were able to discriminate these wild endemic populations from H. annuus and from one of its interspecific hybrids. Most of the variation (71%) observed was within population, and the dendrogram based on shared fragments did not divide the H. argophyllus genotypes into distinct groups resembling different populations. Moreover the hybrid genotypes formed distinguishable subgroups with the cultivated sunflower genotype, confirming the suitability of this technique for taxonomic and phylogenetic studies. From a breeding point of view, although the 12 populations of H. argophyllus represent a new valuable genetic resource, only two of them possessed most of the variation observed, suggesting that they can be the most promising material for crossing with cultivated sunflower.