Study of Inheritance and Linkage of Virulence Genes in a Selfing Population of a Pakistani Dominant Race of Puccinia striiformis f. sp. tritici.

Wheat stripe rust is a severe threat of almost all wheat-growing regions in the world. Being an obligate biotrophic fungus, Puccinia striiformis f. sp. tritici (PST) produces new virulent races that break the resistance of wheat varieties. In this study, 115 progeny isolates were generated through sexual reproduction on susceptible Himalayan Berberis pseudumbellata using a dominant Pakistani race (574232) of PST. The parental isolate and progeny isolates were characterized using 24 wheat Yr single-gene lines and ten simple sequence repeat (SSR) markers. From the one-hundred-and-fifteen progeny isolates, 25 virulence phenotypes (VPs) and 60 multilocus genotypes were identified. The parental and all progeny isolates were avirulent to Yr5, Yr10, Yr15, Yr24, Yr32, Yr32, YrSp, YrTr1, YrExp2, Yr26, and YrTye and virulent to Yr1, Yr2, Yr6, Yr7, Yr8, Yr9, Yr17, Yr25, Yr27, Yr28, YrA, Yr44, and Yr3. Based on the avirulence/virulence phenotypes, we found that VPs virulent to Yr1, Yr2, Yr9, Yr17, Yr47, and YrA were controlled by one dominant gene; those to YrSp, YrTr1, and Yr10 by two dominant genes; and those to YrExp2 by two complementary dominant genes. The results are useful in breeding stripe rust-resistant wheat varieties and understanding virulence diversity.

Comparison of tracheal and nasal chondrocytes for tissue engineering of the trachea.

BACKGROUND: This study was undertaken to evaluate the feasibility of creating engineered tracheal equivalents grown in the shape of cylindrical cartilaginous structures using sheep nasal cartilage-derived chondrocytes. We also tested sheep tracheal and nasal septum for cell yield and quality of the engineered cartilage each produced. METHODS: Nasal septum and tracheal tissue were harvested from sheep. Chondrocytes from each were separately isolated from the tissues and suspended in culture media. Tracheal and nasal chondrocytes were seeded onto separate polyglycolic acid matrices. Cell-polymer constructs were cultured for 1 week and then wrapped around a 7-mm diameter x 30-mm length silicon tube and implanted subcutaneously on the back of nude mice for 8 weeks (each, n = 6). Both of the tissue-engineered tracheas (TET) were harvested and analyzed for histological, biochemical, and biomechanical properties. These values were compared with native sheep trachea. RESULTS: The morphology and histology of both tracheal-chondrocyte TET and nasal-chondrocyte TET closely resembled that of native sheep trachea. Safranin-O staining showed that tissue-engineered cartilage was organized into lobules with round, angular lacunae, each containing a single chondrocyte. Chondrocytes from the trachea or nasal septum produced tissue with similar mechanical properties and had similar glycosaminoglycan and hydroxyproline content. CONCLUSIONS: This study demonstrates that the property of TET using nasal chondrocytes is similar to that obtained using tracheal chondrocytes. This has the potential benefit of facilitating an autologous approach for repair of segmental tracheal defects using an easily obtained chondrocyte population.