The Genome Regions Associated with Abiotic and Biotic Stress Tolerance, as Well as Other Important Breeding Traits in Triticale.

This review article presents the greatest challenges in modern triticale breeding. Genetic maps that were developed and described thus far, together with the quantitative trait loci and candidate genes linked to important traits are also described. The most important part of this review is dedicated to a winter triticale mapping population based on doubled haploid lines obtained from a cross of the cultivars 'Hewo' and 'Magnat'. Many research studies on this population have focused on the analysis of quantitative trait loci regions associated with abiotic (drought and freezing) and biotic (pink snow mold and powdery mildew) stress tolerance as well as related to other important breeding traits such as stem length, plant height, spike length, number of the productive spikelets per spike, number of grains per spike, and thousand kernel weight. In addition, candidate genes located among these regions are described in detail. A comparison analysis of all of these results revealed the location of common quantitative trait loci regions on the rye chromosomes 4R, 5R, and 6R, with a particular emphasis on chromosome 5R. Described here are the candidate genes identified in the above genome regions that may potentially play an important role in the analysis of trait expression. Nevertheless, these results should guide further research using molecular methods of gene identification and it is worth extending the research to other mapping populations. The article is also a review of research led by other authors on the triticale tolerance to the most current stress factors appearing in the breeding.

Genetic mapping of adult-plant resistance genes to powdery mildew in triticale.

Triticale is a cereal of high economic importance; however, along with the increase in the area of this cereal, it is more often infected by the fungal pathogen Blumeria graminis, which causes powdery mildew. The rapid development of molecular biology techniques, in particular methods based on molecular markers may be an important tool used in modern plant breeding. Development of genetic maps, location of the QTLs defining the region of the genome associated with resistance and selection of markers linked to particular trait can be used to select resistant genotypes as well as to pyramidize several resistance genes in one variety. In this paper, we present a new, high-density genetic map of triticale doubled haploids (DH) population "Grenado" × "Zorro" composed of DArT, silicoDArT, and SNP markers. Composite interval mapping method was used to detect eight QTL regions associated with the area under disease progress curve (AUDPC) and 15 regions with the average value of powdery mildew infection (avPM) based on observation conducted in 3-year period in three different locations across the Poland. Two regions on rye chromosome 4R, and single loci on 5R and 6R were reported for the first time as regions associated with powdery mildew resistance. Among all QTLs, 14 candidate genes were identified coded cyclin-dependent kinase, serine/threonine-protein kinase-like protein as well as AMEIOTIC 1 homolog DYAD-like protein, DETOXIFICATION 16-like protein, and putative disease resistance protein RGA3. Three of identified candidate genes were found among newly described QTL regions associated with powdery mildew resistance in triticale.

Quantitative Trait Loci and Candidate Genes Associated with Cold-Acclimation and Microdochium nivale Tolerance/Susceptibility in Winter Triticale (x Triticosecale).

Tolerance to pink snow mold caused by Microdochium nivale appears after a cold-hardening period and it is an essential, genotype-dependent, complex quantitative trait for the wintering of triticale (x Triticosecale) and other cereals. Despite long-term studies, a marker for the selection of the tolerant genotypes is still insufficiently recognized. Chlorophyll fluorescence has been reported as a sensitive indicator of stress effects on photosynthesis and can be used to predict plant tolerance. In this study, the genomic regions (QTLs) associated with the level of winter triticale seedlings damage caused by M. nivale infection as well as photosynthesis quantum efficiency and chlorophyll a fluorescence parameters were identified in seedlings of mapping population of 89 doubled haploids lines (DHs) derived from F1 hybrid of cv. 'Hewo' and cv. 'Magnat' accompanied with the genetic map consisting of 20 linkage groups with a total map length 4997.4 cm. Independent experiments performed in controlled conditions revealed 13 regions identified by a composite interval mapping, located on 7A, 1B, 2B, 6B, 7B, 3R, 5R, and 6R linkage groups and related to the PI, PIABS, TRo/CS, ABS/CS, ABS/CSm, ABS/RC, and Qy values as well as M. nivale tolerance T and susceptibility level P expressed by the seedling damage index. Additionally, candidate genes were in silico identified with the sequence position on wheat (2B and 7B) and rye (5R) chromosomes, where relevant QTL regions were found. The most important candidate genes indicated for M. nivale tolerance of cold-hardened triticale seedlings include those coding: sterol 3-beta-glucosyltransferase UGT80A2-like, transcription factor NAI1-like, and flavonol3-sulfotransferase-like proteins on chromosomes 2B and 5R.

Local and systemic regulation of PSII efficiency in triticale infected by the hemibiotrophic pathogen Microdochium nivale.

Microdochium nivale is a fungal pathogen that causes yield losses of cereals during winter. Cold hardening under light conditions induces genotype-dependent resistance of a plant to infection. We aim to show how photosystem II (PSII) regulation contributes to plant resistance. Using mapping population of triticale doubled haploid lines, three M. nivale strains and different infection assays, we demonstrate that plants that maintain a higher maximum quantum efficiency of PSII show less leaf damage upon infection. The fungus can establish necrotrophic or biotrophic interactions with susceptible or resistant genotypes, respectively. It is suggested that local inhibition of photosynthesis during the infection of sensitive genotypes is not balanced by a supply of energy from the tissue surrounding the infected cells as efficiently as in resistant genotypes. Thus, defence is limited, which in turn results in extensive necrotic damage. Quantitative trait loci regions, involved in the control of both PSII functioning and resistance, were located on chromosomes 4 and 6, similar to a wide range of PSII- and resistance-related genes. A meta-analysis of microarray experiments showed that the expression of genes involved in the repair and de novo assembly of PSII was maintained at a stable level. However, to establish a favourable energy balance for defence, genes encoding PSII proteins resistant to oxidative degradation were downregulated to compensate for the upregulation of defence-related pathways. Finally, we demonstrate that the structural and functional integrity of the plant is a factor required to meet the energy demand of infected cells, photosynthesis-dependent systemic signalling and defence responses.