Genome-wide association mapping of leaf rust and stripe rust resistance in wheat accessions using the 90K SNP array.

KEY MESSAGE: A genome-wide association analysis identified diverse loci for seedling and adult plant resistance to leaf rust and stripe rust. KASP markers were developed and validated for marker-assisted selection. Wheat leaf rust and stripe rust cause significant losses in many wheat producing regions worldwide. The objective of this study was to identify chromosome regions conferring resistance to both leaf rust and stripe rust at the seedling and adult plant stages. A diversity panel of 268 wheat lines, including 207 accessions from different wheat growing regions in China, and 61 accessions from foreign countries, were evaluated for leaf rust response at seedling stage using eight Chinese Puccinia triticina pathotypes, and also tested for leaf rust and stripe rust at adult plant stage in multiple field environments. The panel was genotyped with the Wheat 90 K Illumina iSelect SNP array. Genome-wide association mapping (GWAS) was performed using the mixed linear model (MLM). Twenty-two resistance loci including the known Lr genes, Lr1, Lr26, Lr3ka, LrZH22, and 18 potentially new loci were identified associated with seedling resistance, explaining 4.6 to 25.2% of the phenotypic variance. Twenty-two and 23 adult plant resistance (APR) QTL associated with leaf and stripe rust, respectively, were identified at adult stage, explaining 4.2-11.5% and 4.4-9.7% of the phenotypic variance. Among them, QLr-2BS was the potentially most valuable all-stage resistance gene. Seven and six consistent APR QTL were identified in multiple environments including best linear unbiased prediction (BLUP) data, respectively. Comparison with previously mapped resistance loci indicated that three of the seven leaf rust resistance APR QTL, and two of the six stripe rust resistance APR QTL were new. Four potentially pleiotropic APR QTL, including Lr46/Yr29, QLr-2AL.1/QYr-2AL.1, QLr-2AL.2/QYr-2AL.2, and QLr-5BL/QYr-5BL.1, were identified. Twelve associated SNPs were converted into kompetitive allele-specific PCR (KASP) markers and verified in bi-parental populations. The study reports genetic loci conferring resistance to both diseases, and the closely linked markers should be applicable for marker-assisted wheat breeding.

Clinicopathologic study on a rare variant of ameloblastoma with basal cell features.

OBJECTIVES: To investigate the clinical features, pathologic manifestations, and biologic behaviors of a variant of ameloblastoma with basal cell features (AM-BC). MATERIALS AND METHODS: Following retrospective review of the clinical and pathological data of six cases of AM-BC, we described their histological and immunohistochemical (IHC) features and discussed the biologic behaviors, prognoses, pathogenesis, and clinical relevance of AM-BC. Direct sequencing of polymerase chain reaction products was also performed in all cases. RESULTS: The six cases of AM-BC involved four women and two men, aged 22-82 years. Four lesions occurred in the maxilla and two in the mandible. Histologically, the basal cells tended to be arranged as unequally sized follicles, strands, or cords of odontogenic epithelium in the connective tissue stroma. Little or no stellate reticulum was present in the central portion of the nest. Expression of CKs was consistent with other histological variants of ameloblastoma (AM), but AM-BC had significantly higher p53 and Ki-67 (p < 0.05) labeling indices than other histological variants of AM. Two patients had BRAF gene mutations. CONCLUSION: Ameloblastoma with basal cell features is a very rare variant of AM. Our study showed the differences and relationships that exist between AM-BC and other variants of AM, which could enhance understanding of AM-BC.

Identification of Leaf Rust Resistance Genes in Chinese Common Wheat Cultivars.

Puccinia triticina Eriks. (Pt), the causal agent of wheat (Triticum aestivum L.) leaf rust, is the most widespread disease of common wheat worldwide. In the present study, 83 wheat cultivars from three provinces of China and 36 tester lines with known leaf rust resistance (Lr) genes were inoculated in the greenhouse with 18 Pt pathotypes to identify seedling effective Lr genes. Field tests were also performed to characterize slow leaf rusting responses at the adult plant growth stage in Baoding and Zhoukou in the 2014-15 and 2015-16 cropping seasons. Twelve Lr genes, viz. Lr1, Lr26, Lr3ka, Lr11, Lr10, Lr2b, Lr13, Lr21, Lr34, Lr37, Lr44, and Lr46 either singly or in combination were identified in 41 cultivars. Known Lr genes were not detected in the remaining 42 cultivars. The most commonly identified resistance genes were Lr26 (20 cultivars), Lr46 (18 cultivars), and Lr1 (eight cultivars). Less frequently detected genes included Lr13, Lr34, and Lr37 (each present in four cultivars), Lr10 (three cultivars), and Lr3ka and Lr44 (each in two cultivars). Evidence for the presence of genes Lr11, Lr2b, and Lr21 (each in one cultivar) was also obtained. Seventeen cultivars were found to have slow rusting resistance in both field growing seasons.