Genome-wide association mapping for stripe rust (Puccinia striiformis F. sp. tritici) in US Pacific Northwest winter wheat (Triticum aestivum L.).

KEY MESSAGE: Potential novel and known QTL for race-specific all-stage and adult plant resistance to stripe rust were identified by genome-wide association mapping in the US PNW winter wheat accessions. Stripe rust (Puccinia striiformis F. sp. tritici; also known as yellow rust) is a globally devastating disease of wheat (Triticum aestivum L.) and a major threat to wheat production in the US Pacific Northwest (PNW), therefore both adult plant and all-stage resistance have been introduced into the winter wheat breeding programs in the PNW. The goal of this study was to identify quantitative trait loci (QTL) and molecular markers for these resistances through genome-wide association (GWAS) mapping in winter wheat accessions adapted to the PNW. Stripe rust response for adult plants was evaluated in naturally occurring epidemics in a total of nine environments in Washington State, USA. Seedling response was evaluated with three races under artificial inoculation in the greenhouse. The panel was genotyped with the 9K Illumina Wheat single nucleotide polymorphism (SNP) array and additional markers linked to previously reported genes and QTL for stripe rust resistance. The population was grouped into three sub-populations. Markers linked to Yr17 and previously reported QTL for stripe rust resistance were identified on chromosomes 1B, 2A, and 2B. Potentially novel QTL associated with race-specific seedling response were identified on chromosomes 1B and 1D. Potentially novel QTL associated with adult plant response were located on chromosomes 2A, 2B, 3B, 4A, and 4B. Stripe rust was reduced when multiple alleles for resistance were present. The resistant allele frequencies were different among sub-populations in the panel. This information provides breeders with germplasm and closely linked markers for stripe rust resistance to facilitate the transfer of multiple loci for durable stripe rust resistance into wheat breeding lines and cultivars.

Identification of quantitative trait loci for productive tiller number and its relationship to agronomic traits in spring wheat.

Productive tiller number (PTN), defined as the number of tillers that produce spikes and seeds, is a key component of grain yield in wheat. Spring wheat cultivars in the northern Great Plains of North America differ in PTN. The objectives of this study were (1) to determine the relationship of PTN to agronomic traits using recombinant inbred line (RIL) populations derived from crosses Reeder/Conan, McNeal/Thatcher and Reeder/McNeal grown under a range of environments, and (2) to identify and validate quantitative trait loci (QTL) associated with high PTN. Correlation between PTN and plot weight ranged from r = 0.4-0.6 among the populations based on combined means over years, and was positive in every environment for all crosses (P < 0.05). A genetic map generated for the Reeder/Conan RIL allowed identification of a QTL for PTN consistent over environments, located on chromosome 6B. The QTL on chromosome 6B (QTn.mst-6B) explained 9-17% of the variation of PTN and co-segregated with a QTL for yield in the Reeder/Conan RIL. QTn.mst-6B was validated by single marker analysis in the McNeal/Thatcher RIL, McNeal/Reeder RIL, and a set of near isogenic line (NIL) developed for QTn.mst-6B. The allele for high PTN significantly increased PTN by 8.7, 4, and 13% in the McNeal/Reeder RIL, McNeal/Thatcher RIL and Choteau/Reeder NIL, respectively. The allele for high PTN also had a significant positive effect on plot weight in the McNeal/Reeder RIL. Our results suggest that high PTN, controlled to a significant extent by QTn.mst-6B, contributed to increased yield potential over a range of environmental conditions. QTn.mst-6B may be useful for improving spring wheat in the northern Great Plains of North America and similar environments.

[Diltiazem potentiates the neuromuscular blockade by vecuronium in humans].

We investigated interaction of diltiazem with vecuronium using constant infusion technique in 24 ASA class I or II elective surgical patients with no preoperative administration of Ca antagonists. Neuromuscular blockade was evaluated with accelerometry, which measured single twitch height of adductor pollicis muscle. After tracheal intubation under isoflurane anesthesia, patients received either no diltiazem (control group, n = 8)m, 5 mg (bolus) + 2 mcg.kg-1.min-1 constant infusion (2 mcg group, n = 8) or 5 mg (bolus) + 4 mcg.kg-1.min-1 constant infusion (4 mcg group, n = 8). When single twitch height returned to 10% of control value, infusion of vecuronium was started and the infusion rate was adjusted to maintain twitch height at 10% of the control value. After 30 minutes of stable twitch height, the vecuronium infusion rate and plasma diltiazem concentrations were measured. Diltiazem infusion of 4 mcg.kg-1.min-1 decreased the vecuronium infusion rate by 45% compared with 2 other groups. Plasma diltiazem concentrations in patients receiving 4 mcg.kg-1.min-1 were significantly higher than those receiving 2 mcg.kg-1.min-1. In conclusion diltiazem 4 mcg.kg-1.min-1 potentiates the neuromuscular blockade of vecuronium and it relates with the plasma diltiazem concentration.