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 (CS_m): ABS/CS_m, DI_o/CS_m, TR_o/CS_m, RC/CS_m and ET_o/CS_m, 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.     

A simplified AFLP method for fingerprinting of common wheat (Triticum aestivum L.) cultivars

The simplified AFLP method was developed and evaluated for identification and genetic diversity studies of wheat cultivars. Selective primers exploited in AFLP assay based on a single cutting enzyme PstI ((PstI)AFLP) generated total of 111 robust fragments, including 67 (60%) monomorphic and 12 (11%) cultivar-specific markers. Average similarity between 15 cultivars was 0.650, and varied from 0.293 ('Hope' vs. 'Aurora') to 0.865 ('Norman' vs. 'Hornet'). Mean similarities within groups of winter wheat cultivars with and without 1BL/1RS chromosome were 0.713 and 0.685, respectively. A higher variation was found in the group of spring wheats: 0.677. The obtained results confirm the usefulness of the proposed modification of the AFLP technique for diversity studies and identification of common wheat cultivars.     

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.     

Assessing genetic variation to predict the breeding value of winter triticale cultivars and lines

The objective of this study was to evaluate the usefulness of amplified fragment length polymorphism (AFLP) analyses for selection of the best parents for breeding of hybrid winter triticale. Phenotypic diversity was measured for 8 agronomic traits in 10 parents and 27 F1 hybrids. Genotypic diversity was measured by 91 AFLP markers. Coefficients of correlation of genetic similarity (AFLP-GS) with both Euclidean distances and mean values of the traits were generally not significant. A correction of the preliminary binary matrix into trait-specific derived matrices increased the values of 5 correlation coefficients to a significant level. The correlation of AFLP-GS with mid-parent heterosis of grain weight per plant was low but significant (r = -0.452). Our study confirms the effectiveness of marker preselection for obtaining AFLP-GS better correlated with heterosis. The use of derived matrices is promising for reducing the number of cross combinations tested for specific combining ability.     

Childhood adversity and epigenetic modulation of the leukocyte glucocorticoid receptor: preliminary findings in healthy adults

Background

A history of early adverse experiences is an important risk factor for adult psychopathology. Changes in stress sensitivity and functioning of the hypothalamic-pituitary-adrenal (HPA) axis may underlie the association between stress and risk for psychiatric disorders. Preclinical work in rodents has linked low levels of maternal care to increased methylation of the promoter region of the glucocorticoid receptor (GR) gene, as well as to exaggerated hormonal and behavioral responses to stress. Recent studies have begun to examine whether early-life stress leads to epigenetic modifications of the GR gene in humans.

Methods

We examined the degree of methylation of a region of the promoter of the human GR gene (NR3C1) in leukocyte DNA from 99 healthy adults. Participants reported on their childhood experiences of parental behavior, parental death or desertion, and childhood maltreatment. On a separate day, participants completed the dexamethasone/corticotropin-releasing hormone (Dex/CRH) test, a standardized neuroendocrine challenge test.

Results

Disruption or lack of adequate nurturing, as measured by parental loss, childhood maltreatment, and parental care, was associated with increased NR3C1 promoter methylation (p<.05). In addition, NR3C1 promoter methylation was linked to attenuated cortisol responses to the Dex/CRH test (p<.05).

Conclusions

These findings suggest that childhood maltreatment or adversity may lead to epigenetic modifications of the human GR gene. Alterations in methylation of this gene could underlie the associations between childhood adversity, alterations in stress reactivity, and risk for psychopathology.     

Mapping of QTL and candidate genes associated with powdery mildew resistance in triticale (× Triticosecale Wittm.)

Plant Growth Regulation - Winter rapeseed seedlings are susceptible to low temperature during overwintering in Northwest China, leading to reduced crops production. Freezing stress is one of the...     

PstIAFLP based markers for leaf rust resistance genes in common wheat

The aim of the present study was to detect candidate DNA markers for selected leaf rust resistance genes. A total number of 286 loci in the 'Thatcher' near-isogenic lines carrying resistance gene Lr1, Lr9, Lr10, Lr13, Lr19, Lr21, Lr24, Lr26, Lr28, Lr35, and Lr37 were screened for DNA polymorphism by the PstIAFLP method. A survey with 33 selective primers yielded 16 candidate markers. Further validation studies on cultivars characterized for the presence and absence of selected resistance genes confirmed specificity of markers for Lr24, Lr26 and Lr37. The AFLP-based marker P42-530 was successfully converted into an STS marker. The new marker was linked with the Lr37-specific marker (CslVrga13) at the distance of 1.7 cM. The PstIAFLP method was found to be effective in the identification of DNA changes induced in hexaploid wheat by translocations from Agropyron elongatum, Secale cereale and Aegilops ventricosa.     

Comparative QTL analysis of early short-time drought tolerance in Polish fodder and malting spring barleys

Key message

An effective approach for the further evolution of QTL markers, may be to create mapping populations for locally adapted gene pools, and to phenotype the studied trait under local conditions.

Abstract

Mapping populations of Polish fodder and malting spring barleys (Hordeum vulgare L.) were used to analyze traits describing short-time drought response at the seedlings stage. High-throughput genotyping (Diversity Array Technology (DArT) markers) and phenotyping techniques were used. The results showed high genetic diversity of the studied populations which allowed the creation of high-density linkage maps. There was also high diversity in the physiological responses of the barleys. Quantitative trait locus (QTL) analysis revealed 18 QTLs for nine physiological traits on all chromosomes except 1H in malting barley and 15 QTLs for five physiological traits on chromosomes 2H, 4H, 5H and 6H in fodder barley. Chromosomes 4H and 5H contained QTLs which explained most of the observed phenotypic variations in both populations. There was a major QTL for net photosynthetic rate in the malting barley located on chromosome 5H and two major QTLs for overall photochemical performance (PI) located on 5H and 7H. One major QTL related to photochemical quenching of chlorophyll fluorescence was located on chromosome 4H in fodder barley. Three QTL regions were common to both mapping populations but the corresponding regions explained different drought-induced traits. One region was for QTLs related to PSII photosynthetic activity stress index in malting barley, and the corresponding region in fodder barley was related to the water content stress index. These results are in accordance with previous studies which showed that different traits were responsible for drought tolerance variations in fodder and malting barleys.