Multiple-line cross QTL mapping for biomass yield and plant height in triticale (× Triticosecale Wittmack)

Key message

QTL mapping in multiple families identifies trait-specific and pleiotropic QTL for biomass yield and plant height in triticale.

Abstract

Triticale shows a broad genetic variation for biomass yield which is of interest for a range of purposes, including bioenergy. Plant height is a major contributor to biomass yield and in this study, we investigated the genetic architecture underlying biomass yield and plant height by multiple-line cross QTL mapping. We employed 647 doubled haploid lines from four mapping populations that have been evaluated in four environments and genotyped with 1710 DArT markers. Twelve QTL were identified for plant height and nine for biomass yield which cross-validated explained 59.6 and 38.2 % of the genotypic variance, respectively. A major QTL for both traits was identified on chromosome 5R which likely corresponds to the dominant dwarfing gene Ddw1. In addition, we detected epistatic QTL for plant height and biomass yield which, however, contributed only little to the genetic architecture of the traits. In conclusion, our results demonstrate the potential of genomic approaches for a knowledge-based improvement of biomass yield in triticale.     

Stress treatments influence efficiency of microspore embryogenesis and green plant regeneration in hexaploid triticale (× Triticosecale Wittmack L.)

Doubled haploid (DH) production is a key technology in plant breeding and research. One emerging method of choice for DH production is microspore culture, which requires reprogramming of the microspores from their normal gametophytic development to a sporophytic development resulting in embryo formation. This commonly requires the application of stress such as cold, heat, or starvation. Here, we report the effect of different stress treatments on embryo formation and the proportion of green plants in triticale microspore culture. We observed different responses to the applied stress treatments among three studied genotypes. In general, a 3-wk cold stress treatment performed best with regard to the two criteria. For one genotype, the application of a 24- or 48-h heat stress gave similar or slightly better results and consequently may be an alternative for genotypes that are recalcitrant to the cold stress treatment.     

Fertile,transgenicTriticale ( ×Triticosecale Wittmack)

Fertile transgenicTriticale ( ×Triticosecale Wittmack) plants expressing the-glucuronidase (uidA) and phosphinothricin acetyltransferase (bar) genes were obtained after microprojectile bombardment of scutellar tissue with the plasmid pDB1 containing theuidA gene under the control of the actin-1 promoter (Act1) from rice and the selectable marker genebar under the control of the CaMV 35S promoter. From 465 bombarded scutella about 4000 plantlets were regenerated; 300 plants survived the selection. These regenerants were screened for enzyme activity by the histological GUS assay and by spraying the plants with a herbicide (Basta). Twenty-five regenerants showed GUS activity and survived repeated Basta spraying. Southern blot analysis showed the presence of both marker genes introduced into the genome of analysed plants.All transgenic plants were fertile. They were grown to maturity and set seed. Pollen and progeny analyses provided evidence for inheritance of the introduced genes to the next generation.     

Spike morphology alternations in androgenic progeny of hexaploid triticale (× Triticosecale Wittmack) caused by nullisomy of 2R and 5R chromosomes

Induction of androgenesis, followed by chromosome doubling, is a crucial method to obtain complete homozygosity in one-generation route. However, in vitro androgenesis can result in various genetic and epigenetic changes in derived triticale plants. In this study, we evaluated chromosome alternations and we associated them with the changes of spike morphology in androgenic progeny of triticale. We karyotyped offspring plants that derived from double haploid plants using fluorescence in situ hybridization techniques. We distinguished four major groups of karyotypes: double ditelosomics, nullisomics N2R, nullisomics N5R, and triticale plants with a complete set of chromosomes. It is known that more than half of QTLs connected with androgenic response are located in R-genome of triticale but 2R, 5R, and 6R chromosomes are not included. We hypothesized that the reason why only aberrations of chromosomes 2R and 5R appear during androgenesis of triticale is that because these chromosomes are not involved in the stimulation of androgenic response and the following regeneration of plants is not disrupted. Concerning the established groups, we evaluated following quantitative traits: spike length, number of spikes per plant, number of spikelets per spike, and number of grains per spike. The nullisomy of chromosome 2R and 5R resulted in vast changes in spike architecture of triticale plants, which can be correlated with the location of major QTLs for spike morphology traits on these chromosomes. The spikes of nullisomic plants had significantly decreased spike length which correlated with the reduction of number of spikelets per spike and number of grains per spike.

     

Biolistic Transfer of the Gene uidA and Its Expression in Haploid Embryo-like Structures of Triticale (×Triticosecale Wittmack)

Haploid embryo-like structures (ELS) of triticale were obtained by in vitro androgenesis. These structures were bombarded with gold microparticles 1 µm in diameter coated with the plasmid pAHGUS, using the Dupont PDS He/1000 apparatus. Analysis was made of the influence of genotype, duration of ELS pre-culture, helium pressure and shooting distance on the transfer and expression of the gene uidA. No significant differences were seen between genotypes or duration of pre-culture; differences were found, however, with respect to helium pressure and shooting distance. The combination of 1100 psi helium and a 6 cm shooting distance led to the greatest mean number of uidA expression foci in the ELS (1.63), and the greatest mean number of ELS showing at least one focus (0.38). With a pressure of 1800 psi and a 9 cm distance, only 0.35 foci were obtained per ELS, and only 0.18 ELS had one or more foci. These results are being used as references in a program for obtaining double haploid and transgenic triticale plants.     

Does function follow form? Principal QTLs for Fusarium head blight (FHB) resistance are coincident with QTLs for inflorescence traits and plant height in a doubled-haploid population of barley

Fusarium head blight (FHB), an important disease of barley in many areas of the world, causes losses in grain yield and quality. Deoxynivalenol (DON) mycotoxin residues, produced by the primary pathogen Fusarium graminearum, pose potential health risks. Barley producers may not be able to profitably market FHB-infected barley, even though it has a low DON level. Three types of FHB resistance have been described in wheat: Type I (penetration), Type II (spread), and Type III (mycotoxin degradation). We describe putative measures of these three types of resistance in barley. In wheat, the three resistance mechanisms show quantitative inheritance. Accordingly, to study FHB resistance in barley, we used quantitative trait locus (QTL) mapping to determine the number, genome location, and effects of QTLs associated with Type-I and -II resistance and the concentration of DON in the grain. We also mapped QTLs for plant height, heading date, and morphological attributes of the inflorescence (seeds per inflorescence, inflorescence density, and lateral floret size). QTL analyses were based on a mapping population of F₁-derived doubled-haploid (DH) lines from the cross of the two-rowed genotypes Gobernadora and CMB643, a linkage map constructed with RFLP marker loci, and field evaluations of the three types of FHB resistance performed in China, Mexico, and two environments in North Dakota, USA. Resistance QTLs were detected in six of the seven linkage groups. Alternate favorable alleles were found at the same loci when different inoculation techniques were used to measure Type-I resistance. The largest-effect resistance QTL (for Type-II resistance) was mapped in the centromeric region of chromosome 2. All but two of the resistance QTLs coincided with QTLs determining morphological attributes of the inflorescence and/or plant height. Additional experiments are needed to determine if these coincident QTLs are due to linkage or pleiotropy and to more clearly define the biological basis of the FHB resistance QTLs. Plant architecture should be considered in FHB resistance breeding efforts, particularly those directed at resistance QTL introgression and/or pyramiding. Received: 22 November 1998 / Accepted: 2 June 1999     

Starch Synthesis and Programmed Cell Death during Endosperm Development in Triticale(× Triticosecale Wittmack)

Triticale(× Triticosecale Wittmack) grains synthesize and accumulate starch as their main energy source.Starch accumulation rate and synthesis activities of ADP-glucose pyrophosphorylase,soluble starch synthases,granule-bound starch synthase and starch-branching enzyme showed similar pattern of unimodal curves during endosperm development.There was no significant difference in activity of the starch granule-bound protein isolated from total and separated starch granules at different developmental stages after anthesis in triticale.Evans Blue staining and analysis of DNA fragmentation indicated that cells of triticale endosperm undergo programmed cell death during its development.Dead cells within the endosperm were detected at 6 d post anthesis(DPA),and evidence of DNA fragmentation was first observed at 21 DPA.The period between initial detection of PCD to its rapid increase overlapped with the key stages of rapid starch accumulation during endosperm development.Cell death occurred stochastically throughout the whole endosperm,meanwhile,the activities of starch biosynthetic enzymes and the starch accumulation rate decreased in the late stages of grain filling.These results suggested that the timing and progression of PCD in triticale endosperm may interfere with starch synthesis and accumulation.     

Genetic and molecular characterization of pathogenic isolates of Pyricularia grisea from wheat (Triticum aestivum Lam.) and triticale (x Triticosecale Wittmack) in the state of Paraná, Brazil

Isolates of Pyricularia grisea from wheat (Triticum aestivum Lam.) and triticale (x Triticosecale Wittmack) spikes with blast symptoms were analyzed by classical (VCG) and molecular (RAPD) techniques. P. grisea mutants, unable to use sodium nitrate (nit) as nitrogen source, were obtained with potassium chlorate. For vegetative compatibility (VCG) tests, genetically complementary nit mutant pairs were inoculated in a medium with sodium nitrate as a single nitrogen source. P. grisea isolates were divided into two vegetative compatibility groups and two RAPD groups. Since vegetative compatible strains may mutually exchange genetic and cytoplasmatic material, the contribution of the parasexual cycle in the genetic variability of Brazilian P. grisea isolates is discussed.     

Antioxidant activity and ROS tolerance in triticale (×Triticosecale Wittm.) anthers affect the efficiency of microspore embryogenesis

To verify the hypothesis that cell redox status regulates the process of microspore embryogenesis (ME), reactive oxygen species (ROS) generation and the activity of enzymatic and non-enzymatic antioxidants were analyzed in eight doubled haploid lines of triticale with significant differences in embryogenic potential. The analyses were performed in anthers excised from freshly cut tillers (control) and from low temperature (LT) pre-treated tillers (3 weeks at 4 °C) in which ME has been initiated. Significant associations between ME effectiveness and the variables studied were found. In control cultures, high superoxide dismutase (SOD) activity appeared crucial for microspore viability. On the other hand, positive though non-linear correlation between ME effectiveness and H₂O₂ generation, and negative correlation with catalase (CAT) activity suggest that some threshold level of H₂O₂ is important for successful ME initiation. LT tillers pre-treatment significantly increased H₂O₂ accumulation, which had a negative effect on ME effectiveness. However, even high level of H₂O₂ did not endanger cell viability as long as the cells exhibited high activity of ROS-decomposing enzymes (SOD, CAT and POX). The ability to sustain antioxidative enzyme activity under cold stress in the dark was another important requirement for high effectiveness of ME, allowing for the generation of the signal initiating microspore reprogramming and simultaneously protecting the cells from the toxic effects of ROS production. The role of antioxidative enzymes cannot be replaced even by high activity of non-enzymatic antioxidants. In conclusion, genetically controlled but environmentally modified cell tolerance to oxidative stress seems to play an important role in triticale ME.     

Anther extrusion and plant height are associated with Type I resistance to Fusarium head blight in bread wheat line ‘Shanghai-3/Catbird’

Fusarium head blight (FHB) is a destructive wheat disease of global importance. Resistance breeding depends heavily on the Fhb1 gene. The CIMMYT line Shanghai-3/Catbird (SHA3/CBRD) is a promising source without this gene. A recombinant inbred line (RIL) population from the cross of SHA3/CBRD with the German spring wheat cv. Naxos was evaluated for FHB resistance and related traits in field trials using spray and spawn inoculation in Norway and point inoculation in China. After spray and spawn inoculation, FHB severities were negatively correlated with both anther extrusion (AE) and plant height (PH). The QTL analysis showed that the Rht-B1b dwarfing allele co-localized with a QTL for low AE and increased susceptibility after spawn and spray inoculation. In general, SHA3/CBRD contributed most of the favorable alleles for resistance to severity after spray and spawn inoculation, while Naxos contributed more favorable alleles for reduction in FDK and DON content and resistance to severity after point inoculation. SHA3/CBRD contributed a major resistance QTL close to the centromere on 2DLc affecting FHB severity and DON after all inoculation methods. This QTL was also associated with AE and PH, with high AE and tall alleles contributed by SHA3/CBRD. Several QTL for AE and PH were detected, and low AE or reduced PH was always associated with increased susceptibility after spawn and spray inoculation. Most of the other minor FHB resistance QTL from SHA3/CBRD were associated with AE or PH, while the QTL from Naxos were mostly not. After point inoculation, no other QTL for FHB traits was associated with AE or PH, except the 2DLc QTL which was common across all inoculation methods. Marker-assisted selection based on the 2DLc QTL from SHA3/CBRD combined with phenotypic selection for AE is recommended for resistance breeding based on this valuable source of resistance.     

Microbiological and Sybr® Green real-time PCR detection of major Fusarium head blight pathogens on wheat ears

Fusarium head blight (FHB) caused by several Fusarium species is one of the most serious diseases affecting wheat throughout the world. The efficiency of microbiological assays and real-time PCR to quantify major FHB pathogens in wheat ears after inoculation with F. graminearum, F. culmorum, F. avenaceum and F. poae under greenhouse and field conditions were evaluated. The frequency of infected kernel, content of fungal biomass, disease severity and kernel weight were determined. To measure the fungal biomass an improved DNA extraction method and a Sybr® Green real-time PCR were developed. The Sybr® Green real-time PCR proved to be highly specific for individual detection of the species in a matrix including fungal and plant DNA. The effect of Fusarium infection on visible FHB severity, frequency of infected kernels and thousand-kernel mass (TKM) significantly depended on the Fusarium species/isolate. F. graminearum resulted in highest disease level, frequency of infected kernels, content of fungal biomass, and TKM reduction followed by F. culmorum, F. avenaceum and F. poae, respectively. The comparison of frequency and intensity of kernel colonization proved differences in aggressiveness and development of the fungi in the kernels. Only for F. graminearum, the most aggressive isolate, application of microbiological and real-time PCR assays gave similar results. For the other species, the intensity of kernel colonization was lower than expected from the frequency of infection.     

Genetic mapping of QTL for resistance to Fusarium head blight spread (type 2 resistance) in a Triticum dicoccoides × Triticum durum backcross-derived population

Improvement of resistance to Fusarium head blight (FHB) is a continuous challenge for durum wheat breeders, particularly due to the limited genetic variation within this crop species. We accordingly generated a backcross-derived mapping population using the type 2 FHB resistant Triticum dicoccoides line Mt. Gerizim #36 as donor and the modern Austrian T. durum cultivar Helidur as recipient; 103 BC₁F_6:7 lines were phenotyped for type 2 FHB resistance using single-spikelet inoculations and genotyped with 421 DNA markers (SSR and AFLP). QTL mapping revealed two highly significant QTL, mapping to chromosomes 3A and 6B, respectively. For both QTL the T. dicoccoides allele improved type 2 FHB resistance. Recombinant lines with both favorable alleles fixed conferred high resistance to FHB similar to that observed in the T. dicoccoides parent. The results appear directly applicable for durum wheat resistance breeding.     

Impact of epistasis and QTL×environment interaction on the developmental behavior of plant height in rice (Oryza sativa L.)

QTLs with epistatic effects and environmental interaction effects for the developmental behavior of plant height in rice were studied by conventional and conditional methods for quantitative trait loci (QTLs) by mapping with a doubled-haploid population of 123 lines from IR64/Azucena in three environments. The results showed that epistatic effects were important and most epistasis could be detected only by conditional QTL mapping, while most non–epistatic QTLs could be detected by both conventional and conditional methods. Many modificative QTLs showed only epistatic effects without their own additive effects at some stages. QTL×environment (QE) interaction effects were detected more often than QTL main effects for plant-height behavior, which might indicate that gene expression could be greatly affected by the environment. No QTLs had effects during the whole of ontogeny. Conditional QTL mapping might be a valid way to reveal dynamic gene expression for the development of quantitative traits, especially for epistatic effects. Received: 19 May 2000 / Accepted: 27 October 2000     

Analysis of QTL×environment interaction for yield components and plant height in rice

 An F₂ and two equivalent F₃ populations of an indica-indica cross of rice, Tesanai 2/CB, were constructed and grown in different environments. The identification of quantitative trait loci (QTL) for yield components and plant height and an analysis of QTL×environment interaction were conducted for three trials. Interval mapping of QTL for eight traits was employed with a threshold of LOD=2 using the computer package MAPMAKER/QTL. A total of 44 QTL were detected in 18 intervals of nine chromosomes, including 3 for the number of panicles (NP), 5 for the number of filled grains (NFG), 6 for total number of spikelets (TNS), 3 for spikelet fertility (SF), 7 for 1000-grain weight (TGWT), 5 for grain weight per plant (GWT), 8 for plant height (PH) and 7 for panicle length (PL). The numbers of QTL detected in two or three trials were 1 for NP, 1 for NFG, 1 for TNS, none for SF, 4 for TGWT, 3 for GWT, 2 for PH and 5 for PL, making a total of 17. When a QTL was detected in more than one trial the direction and magnitude of its additive effect, the dominance effect and the degree of dominance were generally in good agreement. In all three trials, QTL were frequently detected for related traits in the same intervals. The directions of additive effect of QTL for related traits in a given interval were in agreement with few exceptions, no matter whether they were detected in the same trial or not. This result suggested that pleiotropism rather than close linkage of different QTL was the major reason why QTL for different traits were frequently detected in the same intervals. When gene pleiotropism was considered, 23 of the 29 QTL for yield and its components and 9 of the 15 QTL for plant stature were detected in more than one trial. This indicated that the detection of chromosomal segments harboring QTL was hardly affected by environmental factors. Received: 30 January 1997 / Accepted: 21 March 1997     

Effects of rye and triticale seed proteins on Leptinotarsa decemlineata (Say) digestive α-amylase and protease and some biological parameters

The current study aimed to investigate the effect of rye and triticale seed proteins on the Leptinotarsa decemlineata, gut enzymes. Results showed that ammonium sulphate precipitation fractions; 0–30, 30–50, 50–70 and 70–100% had no inhibition on the fourth instar larval (L₄) protease activity, while first two fractions of triticale and all fractions of rye had inhibitory effects on the all larval stages and adult’s α-amylase activity. Mode of inhibition in rye and triticale was partial mixed and uncompetitive, respectively. Zymograms approved the results. Feeding assays were conducted using four cultivars of potato leaves treated with extracts. Weight of L₄ on Marx in both trials and the L₄ evolution in all cultivars in rye and just on Picasso in triticale were reduced, the developmental durations were increased on Marx and Picasso in triticale trial significantly. Also, rye extract caused inhibition in amylase activity of survived individuals that feed from treated Burren leaves.     

Isolates of Fusarium graminearum collected 40–320?meters above ground level cause Fusarium head blight in wheat and produce trichothecene mycotoxins

The aerobiology of fungi in the genus Fusarium is poorly understood. Many species of Fusarium are important pathogens of plants and animals and some produce dangerous secondary metabolites known as mycotoxins. In 2006 and 2007, autonomous unmanned aerial vehicles (UAVs) were used to collect Fusarium 40–320 m above the ground at the Kentland Farm in Blacksburg, Virginia. Eleven single-spored isolates of Fusarium graminearum (sexual stage Gibberella zeae) collected with autonomous UAVs during fall, winter, spring, and summer months caused Fusarium head blight on a susceptible cultivar of spring wheat. Trichothecene genotypes were determined for all 11 of the isolates; nine isolates were DON/15ADON, one isolate was DON/3ADON, and one isolate was NIV. All of the isolates produced trichothecene mycotoxins in planta consistent with their trichothecene genotypes. To our knowledge, this is the first report of a NIV isolate of F. graminearum in Virginia, and DON/3ADON genotypes are rare in populations of the fungus recovered from infected wheat plants in the eastern United States. Our data are considered in the context of a new aerobiological framework based on atmospheric transport barriers, which are Lagrangian coherent structures present in the mesoscale atmospheric flow. This framework aims to improve our understanding of population shifts of F. graminearum and develop new paradigms that may link field and atmospheric populations of toxigenic Fusarium spp. in the future.     

Mapping of QTL for Fusarium head blight resistance and morphological and developmental traits in three backcross populations derived from Triticum dicoccum?×?Triticum durum

Breeding for resistance to Fusarium head blight (FHB) in durum wheat continues to be hindered by the lack of effective resistance sources. Only limited information is available on resistance QTL for FHB in tetraploid wheat. In this study, resistance to FHB of a Triticum dicoccum line in the background of three Austrian T. durum cultivars was genetically characterized. Three populations of BC₁F₄-derived RILs were developed from crosses between the resistant donor line T. dicoccum-161 and the Austrian T. durum recipient varieties DS-131621, Floradur and Helidur. About 130 BC₁F₄-derived lines per population were evaluated for FHB response using artificial spray inoculation in four field experiments during two seasons. Lines were genetically fingerprinted using SSR and AFLP markers. Genomic regions on chromosomes 3B, 4B, 6A, 6B and 7B were significantly associated with FHB severity. FHB resistance QTL on 6B and 7B were identified in two populations and a resistance QTL on 4B appeared in three populations. The alleles that enhanced FHB resistance were derived from the T. dicoccum parent, except for the QTL on chromosome 3B. All QTL except the QTL on 6A mapped to genomic regions where QTL for FHB have previously been reported in hexaploid wheat. QTL on 3B and 6B coincided with Fhb1 and Fhb2, respectively. This implies that tetraploid and hexaploid wheat share common genomic regions associated with FHB resistance. QTL for FHB resistance on 4B co-located with a major QTL for plant height and mapped at the position of the Rht-B1 gene, while QTL on 7B overlapped with QTL for flowering time.