Identification of Pm58 from Aegilops tauschii.

KEY MESSAGE: A novel powdery mildew-resistance gene, designated Pm58, was introgressed directly from Aegilops tauschii to hexaploid wheat, mapped to chromosome 2DS, and confirmed to be effective under field conditions. Selectable KASP™ markers were developed for MAS. Powdery mildew caused by Blumeria graminis (DC.) f. sp. tritici (Bgt) remains a significant threat to wheat (Triticum aestivum L.) production. The rapid breakdown of race-specific resistance to Bgt reinforces the need to identify novel sources of resistance. The D-genome species, Aegilops tauschii, is an excellent source of disease resistance that is transferrable to T. aestivum. The powdery mildew-resistant Ae. tauschii accession TA1662 (2n = 2x = DD) was crossed directly with the susceptible hard white wheat line KS05HW14 (2n = 6x = AABBDD) followed by backcrossing to develop a population of 96 BC2F4 introgression lines (ILs). Genotyping-by-sequencing was used to develop a genome-wide genetic map that was anchored to the Ae. tauschii reference genome. A detached-leaf Bgt assay was used to screen BC2F4:6 ILs, and resistance was found to segregate as a single locus (χ = 2.0, P value = 0.157). The resistance gene, referred to as Pm58, mapped to chromosome 2DS. Pm58 was evaluated under field conditions in replicated trials in 2015 and 2016. In both years, a single QTL spanning the Pm58 locus was identified that reduced powdery mildew severity and explained 21% of field variation (P value < 0.01). KASP™ assays were developed from closely linked GBS-SNP markers, a refined genetic map was developed, and four markers that cosegregate with Pm58 were identified. This novel source of powdery mildew-resistance and closely linked genetic markers will support efforts to develop wheat varieties with powdery mildew resistance.

Fine mapping of the stem rust resistance gene SrTA10187.

KEY MESSAGE: SrTA10187 was fine-mapped to a 1.1 cM interval, candidate genes were identified in the region of interest, and molecular markers were developed for marker-assisted selection and Sr gene pyramiding. Stem rust (Puccinia graminis f. sp. tritici, Pgt) races belonging to the Ug99 (TTKSK) race group pose a serious threat to global wheat (Triticum aestivum L.) production. To improve Pgt host resistance, the Ug99-effective resistance gene SrTA10187 previously identified in Aegilops tauschii Coss. was introgressed into wheat, and mapped to the short arm of wheat chromosome 6D. In this study, high-resolution mapping of SrTA10187 was done using a population of 1,060 plants. Pgt resistance was screened using race QFCSC. PCR-based SNP and STS markers were developed from genotyping-by-sequencing tags and SNP sequences available in online databases. SrTA10187 segregated as expected in a 3:1 ratio of resistant to susceptible individuals in three out of six BC3F2 families, and was fine-mapped to a 1.1 cM region on wheat chromosome 6DS. Marker context sequence was aligned to the reference Ae. tauschii genome to identify the physical region encompassing SrTA10187. Due to the size of the corresponding region, candidate disease resistance genes could not be identified with confidence. Comparisons with the Ae. tauschii genetic map developed by Luo et al. (PNAS 110(19):7940-7945, 2013) enabled identification of a discrete genetic locus and a BAC minimum tiling path of the region spanning SrTA10187. Annotation of pooled BAC library sequences led to the identification of candidate genes in the region of interest-including a single NB-ARC-LRR gene. The shorter genetic interval and flanking KASP™ and STS markers developed in this study will facilitate marker-assisted selection, gene pyramiding, and positional cloning of SrTA10187.

Simultaneous transfer, introgression, and genomic localization of genes for resistance to stem rust race TTKSK (Ug99) from Aegilops tauschii to wheat.

Wheat production is currently threatened by widely virulent races of the wheat stem rust fungus, Puccinia graminis f. sp. tritici, that are part of the TTKSK (also known as 'Ug99') race group. The diploid D genome donor species Aegilops tauschii (2n = 2x = 14, DD) is a readily accessible source of resistance to TTKSK and its derivatives that can be transferred to hexaploid wheat, Triticum aestivum (2n = 6x = 42, AABBDD). To expedite transfer of TTKSK resistance from Ae. tauschii, a direct hybridization approach was undertaken that integrates gene transfer, mapping, and introgression into one process. Direct crossing of Ae. tauschii accessions with an elite wheat breeding line combines the steps of gene transfer and introgression while development of mapping populations during gene transfer enables the identification of closely linked markers. Direct crosses were made using TTKSK-resistant Ae. tauschii accessions TA1662 and PI 603225 as males and a stem rust-susceptible T. aestivum breeding line, KS05HW14, as a female. Embryo rescue enabled recovery of F1 (ABDD) plants that were backcrossed as females to the hexaploid recurrent parent. Stem rust-resistant BC1F1 plants from each Ae. tauschii donor source were used as males to generate BC2F1 mapping populations. Bulked segregant analysis of BC2F1 genotypes was performed using 70 SSR loci distributed across the D genome. Using this approach, stem rust resistance genes from both accessions were located on chromosome arm 1DS and mapped using SSR and EST-STS markers. An allelism test indicated the stem rust resistance gene transferred from PI 603225 is Sr33. Race specificity suggests the stem rust resistance gene transferred from TA1662 is unique and this gene has been temporarily designated SrTA1662. Stem rust resistance genes derived from TA1662 and PI 603225 have been made available with selectable molecular markers in genetic backgrounds suitable for stem rust resistance breeding.

Introgression of stem rust resistance genes SrTA10187 and SrTA10171 from Aegilops tauschii to wheat.

Aegilops tauschii, the diploid progenitor of the wheat D genome, is a readily accessible germplasm pool for wheat breeding as genes can be transferred to elite wheat cultivars through direct hybridization followed by backcrossing. Gene transfer and genetic mapping can be integrated by developing mapping populations during backcrossing. Using direct crossing, two genes for resistance to the African stem rust fungus race TTKSK (Ug99), were transferred from the Ae. tauschii accessions TA10187 and TA10171 to an elite hard winter wheat line, KS05HW14. BC2 mapping populations were created concurrently with developing advanced backcross lines carrying rust resistance. Bulked segregant analysis on the BC2 populations identified marker loci on 6DS and 7DS linked to stem rust resistance genes transferred from TA10187 and TA10171, respectively. Linkage maps were developed for both genes and closely linked markers reported in this study will be useful for selection and pyramiding with other Ug99-effective stem rust resistance genes. The Ae. tauschii-derived resistance genes were temporarily designated SrTA10187 and SrTA10171 and will serve as valuable resources for stem rust resistance breeding.

Hypertriglyceridemia and pancreatitis associated with estramustine phosphate.

Estramustine phosphate is associated with estrogenic complications. However, hypertriglyceridemia has not yet been associated with estramustine phosphate. We describe a patient in whom severe hypertriglyceridemia and pancreatitis developed after treatment with estramustine phosphate. A 59-year-old man with hormone-refractory prostate cancer was treated with estramustine phosphate, docetaxel, and carboplatin. After three cycles, the patient was admitted with triglyceride levels of 12,210 mg/dl and pancreatitis. After resolution of hypertriglyceridemia and pancreatitis, chemotherapy with docetaxel and carboplatin was continued without recurrence of hypertriglyceridemia. We conclude that estramustine phosphate has the potential to cause hypertriglyceridemia in susceptible individuals.

Erythromycin improves gastric emptying half-time in adult cystic fibrosis patients with gastroparesis.

BACKGROUND: Gastrointestinal manifestations are frequently encountered in cystic fibrosis patients. Gastroparesis evidenced by a variety of diagnostic methods has been described in patients with cystic fibrosis, predominantly in children and in individuals with advanced lung disease. The presence of gastroparesis in adult patients with different degrees of lung involvement and its response to the acute and chronic administration of macrolides have not been reported. METHODS: Using the University of Florida Cystic Fibrosis database we identified symptomatic patients who had gastroparesis confirmed by a prolonged half-time during gastric emptying scintigraphy. RESULTS: Of 86 cystic fibrosis patients, periodically followed in our institution, we found five who had classical symptoms and prolonged gastric emptying half-time. Age 25.2+/-8 years, 80% females, BMI 22+/-9 kg/m(2), HbA1c 5.8+/-0.6 g/dl, FEV1 53.2+/-15% of predicted. Gastric emptying half-time was 191.4+/-91.4 min (range 100-300 min) and decreased to 12.2+/-6 min (range 5-20 min) after IV administration of erythromycin (p=0.043). Patients were followed up for 3+/-2.1 years. All patients but one, who was taking opiods, had good clinical response to PO macrolides. CONCLUSIONS: Gastroparesis occurs in patients with cystic fibrosis, even in patients with relatively preserved lung function and in those without cystic-fibrosis related diabetes. Macrolides may be an effective therapy in cystic fibrosis patients with gastroparesis when administered acutely or chronically.