Maximizing pre-harvest sprouting in white- and red-seeded wheat

Non-Peer ReviewedSeed dormancy is the main factor responsible for conferring pre-harvest sprouting tolerance to wheat grain. Recently, five common wheat germplasm lines (W98616, Line 211, CDC EMDR-4, CDC EMDR-9, and CDC EMDR-14) with deep seed dormancy levels and differing genetic backgrounds were released by the Crop Development Centre, University of Saskatchewan. The objective of this presentation is to give an overview of (1) the five CDC germplasm lines, (2) the two dormancy breaking methods that effectively overcome the deep seed dormancy levels in the five CDC germplasm lines, and (3) how the two dormancy breaking method can be used by breeders to improve sprouting tolerance within their breeding programs using the five CDC germplasm lines

Influence of local fullerene orientation on the electronic properties of A3C60 compounds

We have investigated sodium containing fullerene superconductors Na2AC60, A = Cs, Rb, and K, by Na-23 nuclear magnetic resonance (NMR) spectroscopy at 7.5 T in the temperature range of 10 to 400 K. Despite the structural differences from the Rb3C60 class of fullerene superconductors, in these compounds the NMR line of the tetrahedrally coordinated alkali nuclei also splits into two lines (T and T') at low temperature. In Na2CsC60 the splitting occurs at 170 K; in the quenched cubic phase of Na2RbC60 and Na2KC60 we observe split lines at 80 K. Detailed investigations of the spectrum, spin-spin and spin-lattice relaxation as well as spin-echo double resonance (SEDOR) in Na2CsC60 we show that these two different tetrahedral sites are mixed on a microscopic scale. The T and T' sites differ in the orientation of first-neighbor C60 molecules. We present evidence that the orientations of neighboring molecules are uncorrelated. Thermally activated molecular reorientations cause an exchange between the T and T' sites and motional narrowing at high temperature. We infer the same activation energy, 3300 K, in the temperature range 125 to 300 K. The spin lattice relaxation rate is the same for T and T' down to 125 K but different below. Both the spin-lattice relaxation rate and Knight shift are strongly temperature dependent in the whole range investigated. We interpret this temperature variation by the effect of phonon excitations involving the rigid librational motion of the C60 molecules. By extending the understanding of the structure and molecular dynamics of C60 superconductors, these results may help in clarifying the effects of the structure on the superconducting properties.Comment: 13 pages, 10 figures, submitted to PR

Isolation distances for minimizing out-crossing in spring wheat

Non-Peer ReviewedCurrently recommended isolation distances of three or 10 m for pedigreed seed production of spring wheat (Triticum aestivum L.) may not be sufficient for cultivars with high out-crossing (OC) rates. The detection of higher than expected OC rates in wheat has directed this research to reassess currently recommended minimum isolation distances. The objective of this study was to determine if increased isolation distances are needed for cultivars that exhibit higher than normal levels of out-crossing. In each of two years, OC rates were determined for four Canadian spring wheat cultivars at each of 15 distances (0-33 m) from a blue aleurone pollen source. Cultivars were grown in rows perpendicular to the pollinator block to the north, south, west, & east. Target rows were replicated four times within each direction. Out-crossing in ‘Katepwa’ & ‘Biggar’ was not detected beyond three meters. Cultivars ‘Roblin’ & ‘Oslo’ exhibited higher than normal OC at distances of up to 27m. For Roblin & Oslo, an isolation distance of 30m is recommended to mitigate OC-derived off-types in the subsequent generation of pedigreed seed

Skin effect as a probe of transport regimes in Weyl semimetals

We study the propagation of an oscillatory electromagnetic field inside a Weyl semimetal. In conventional conductors, the motion of the charge carriers in the skin layer near the surface can be diffusive, ballistic, or hydrodynamic. We show that the presence of chiral anomalies, intrinsic to the massless Weyl particles, leads to a hitherto neglected nonlocal regime that can separate the normal and viscous skin effects. We propose to use this regime as a diagnostic of the presence of chiral anomalies in optical conductivity measurements. These results are obtained from a generalized kinetic theory that includes various relaxation mechanisms, allowing us to investigate different transport regimes of Weyl semimetals

Seed dormancy and germination in three annual canarygrass (Phalaris canariensis L.) cultivars relative to spring wheat (Triticum aestivum L.)

Non-Peer ReviewedSeed dormancy in annual canarygrass may lead to unsatisfactory germination in seed tests. The objectives of this study were (i) to quantify the levels of seed dormancy in three morphologically diverse annual canarygrass cultivars (‘Keet’, ‘CDC Maria’, & ‘CY 184’) relative to spring wheat & (ii) to determine the effectiveness of three treatments (GA3, KNO3, & chilling) & two temperature regimes (15/25°C & 15°C) in promoting germination of dormant annual canarygrass seeds. The hard red spring wheat cultivar ‘Katepwa’ control was included as a representative of a cereal crop that has been extensively characterized with regards to seed dormancy. In 1998 & 1999, the four cultivars were grown at Saskatoon, Canada. At maturity, panicles & spikes were hand harvested & stored at –20°C. Four replications of 50 seeds per cultivar were used in each experiment. Three experiments were conducted: (i) seeds were germinated at 10, 15, 20, & 25°C for one week, (ii) seeds were stored at 24°C for zero to eight weeks prior to germination at 22°C for one week, & (iii) seeds were treated with GA3, KNO3, & chilling prior to germination at 15/25°C (16/8h) or 15°C for two weeks. For experiment one & three, a split-plot analysis was used to analyze arc sin transformed percentage germination data. Average percentage germination data in experiment two were tested to be significantly different from 98% germination (P=0.05) based on one-tailed t-tests. Annual canarygrass developed deeper dormancy than the wheat cultivar in both years, particularly when germinated at 20 & 25°C. The highest percentage germination was observed at 15°C. Two (1998) & four weeks (1999) of storage at 24°C were required to overcome dormancy in annual canarygrass. Pre-chilling or KNO3 treatment prior to germination at 15/25°C (16/8h in darkness) resulted in average germination levels of 94% (1998) & 66% (1999). Potassium nitrate treatment prior to incubation at 15°C in darkness was the most effective method of promoting germination in dormant seeds, resulting in 99% (1998) & 97% (1999) germination. Thus, we recommend the use of the latter method, instead of the former or currently recommended method (pre-chilling or KNO3 treatment prior to germination at 15/25°C [16/8h] in darkness), for testing germination levels of dormant seed of annual canarygrass

Applying Fishers' Ecological Knowledge to Construct Past and Future Lobster Stocks in the Juan Fernández Archipelago, Chile

Over-exploited fisheries are a common feature of the modern world and a range of solutions including area closures (marine reserves; MRs), effort reduction, gear changes, ecosystem-based management, incentives and co-management have been suggested as techniques to rebuild over-fished populations. Historic accounts of lobster (Jasus frontalis) on the Chilean Juan Fernández Archipelago indicate a high abundance at all depths (intertidal to approximately 165 m), but presently lobsters are found almost exclusively in deeper regions of their natural distribution. Fishers' ecological knowledge (FEK) tells a story of serial depletion in lobster abundance at fishing grounds located closest to the fishing port with an associated decline in catch per unit effort (CPUE) throughout recent history. We have re-constructed baselines of lobster biomass throughout human history on the archipelago using historic data, the fishery catch record and FEK to permit examination of the potential effects of MRs, effort reduction and co-management (stewardship of catch) to restore stocks. We employed a bioeconomic model using FEK, fishery catch and effort data, underwater survey information, predicted population growth and response to MR protection (no-take) to explore different management strategies and their trade-offs to restore stocks and improve catches. Our findings indicate that increased stewardship of catch coupled with 30% area closure (MR) provides the best option to reconstruct historic baselines. Based on model predictions, continued exploitation under the current management scheme is highly influenced by annual fluctuations and unsustainable. We propose a community-based co-management program to implement a MR in order to rebuild the lobster population while also providing conservation protection for marine species endemic to the Archipelago

Optical excitations in hexagonal nanonetwork materials

Optical excitations in hexagonal nanonetwork materials, for example, Boron-Nitride (BN) sheets and nanotubes, are investigated theoretically. The bonding of BN systems is positively polarized at the B site, and is negatively polarized at the N site. There is a permanent electric dipole moment along the BN bond, whose direction is from the B site to the N site. When the exciton hopping integral is restricted to the nearest neighbors, the flat band of the exciton appears at the lowest energy. The higher optical excitations have excitation bands similar to the electronic bands of graphene planes and carbon nanotubes. The symmetry of the flat exciton band is optically forbidden, indicating that the excitons related to this band will show quite long lifetime which will cause strong luminescence properties.Comment: 4 pages; 3 figures; proceedings of "XVIth International Winterschool on Electronic Properties of Novel Materials (IWEPNM2002)

Genetic mapping of pre-harvest sprouting resistance loci in bread wheat (Triticum aestivum L.)

Non-Peer ReviewedPre-harvest sprouting (PHS) in bread wheat (Triticum aestivum L.) is the germination of mature grain while still in spike. PHS causes downgrading of grain quality which severely limits its end use. In western Canada, cool and wet weather during harvest makes the crops susceptible to PHS. Breeding for PHS tolerance in wheat is challenging on phenotypic basis because PHS is inherited quantitatively and strongly affected by environmental conditions. A mapping population of one hundred and fifty one doubled haploid (DH) lines from a cross between two spring wheat cultivars ND690 (non-dormant) and W98616 (dormant) was developed for genetic mapping of PHS resistance loci. Initially, 20 dormant and 20 non dormant lines were used for genetic mapping with SSR (Simple sequence repeat) and AFLP (Amplified Fragment Length Polymorphism) markers. A total of 550 markers (300 SSR markers and 250 AFLP) markers have been mapped on different chromosomes. Five chromosomal regions on the chromosomes 1A, 3B, 4A, 5B and 6B associated with pre-harvest sprouting were identified in this study

Identification and validation of QTLs associated with pre-harvest sprouting tolerance in bread wheat

Non-Peer ReviewedPre-harvest sprouting (PHS) is the in-spike germination of physiologically mature grain in response to relatively high humidity due to untimely rains prior to harvest. PHS in bread wheat (Triticum aestivum L.) results in substantial economic loss, as it decreases the functional quality of wheat grain. The Canadian Grain Commission sets the limit of percentage severely sprouted and total sprouted grain depending on the grade and wheat classes. Pre-harvest sprouted wheat is reduced in grade and value, depending on the quantity of sprouted kernels present in a sample. Breeding for PHS tolerance in wheat is challenging on phenotypic basis because PHS is inherited quantitatively and highly influenced by environmental conditions. Seed dormancy is the main factor responsible for conferring the PHS resistance to the grains of bread wheat. The objectives of this study were to identify and validate the major quantitative loci (QTL) for pre-harvest sprouting (PHS) resistance in bread wheat. A F1-derived doubled haploid (DH) population of 151 lines from a cross between two spring wheat cultivars ND690 (nondormant) and W98616 (dormant) was used to identify the genomic regions associated with PHS tolerance. A total of 950 polymorphic markers (369 SSR, 306 AFLP, 267 DArT and 8 EST) have been used to develop a genetic map and to identify QTLs for PHS tolerance. Interval mapping revealed a major QTL on chromosome 4A explaining 25% phenotypic variation in this mapping population. Forty two Canadian wheat cultivars and germplasm lines were screened with the DNA marker in the QTL region on chromosome 4A for validation. 113 BC1F1 plants from four different backcrosses were screened with the marker associated with PHS resistance. Marker assisted back crossing reduced the population size in BC1F1 generation by 40.7%. This information will help the plant breeders to pyramid this QTL with other QTLs from different PHS resistance sources