In semiarid areas, cereal crops often allocate more biomass to root at the expense of aboveground yield. A pot experiment was conducted to investigate carbon consumption of roots and its impact on grain yield of spring wheat (Triticum aestivum L.) as affected by water and phosphorus (P) supply. A factorial design was used with six treatments namely two water regimes (at 80–75% and 50–45% field capacity (FC)) and three P supply rates (P1=0, P2=44 and P3=109 µg P g^–1 soil). At shooting and flowering stages, root respiration and carbon consumption increased with the elevate of P supply rates, regardless of water conditions, which achieved the minimum and maximum at P1 under 50–45% FC and P3 under 80–75% FC, respectively. However, total aboveground biomass and grain yield were higher at P2 under 80–75% FC; and decreased with high P application (P3). The results indicated that rational or low P supply (80–75% of field water capacity and 44 mg P kg^–1 soil) should be recommended to improve grain yield by decreasing root carbon consumption in semiarid areas.

Stripe rust, caused by Puccinia striiformis Westend. f. sp. tritici (Pst), is a severe foliar disease of common wheat (Triticum aestivum L.) in the world. Resistance is the best approach to control the disease. The winter wheat cultivar Lantian 1 has high-temperature resistance to stripe rust. To determing the gene(s) for the stripe rust resistance, Lantian 1 was crossed with Mingxian 169 (M169). Seedlings of the parents, and F1, F2 and F2-3 progenies were tested with races CYR32 of Pst under controlled greenhouse conditions. Lantian 1 has a single partially dominant gene conferred resistance to race CYR32, designated as YrLT1. Simple sequence repeat (SSR) techniques were used to identify molecular markers linked to YrLT1. A linkage group of five SSR markers was constructed for YrLT1 using 166 F2 plants. Based on the SSR marker consensus map and the position on wheat chromosome, the resistance gene was assigned on chromosome 2DL. Amplification of a set of nulli-tetrasomic Chinese Spring lines with SSR marker Xwmc797 confirmed that the resistance gene was located on the long arm of chromosome 2D. Because of its chromosomal location and the high-temperature resistance, this gene is different from previously described genes. The molecular map spanned 29.9 cM, and the genetic distance of two close markers Xbarc228 and Xcfd16 to resistance gene locus was 4.0 and 5.7 cM, respectively. The polymorphism rates of the flanking markers in 46 wheat lines were 2.1 and 2.1%, respectively; and the two markers in combination could distinguish the alleles at the resistance locus in 97.9% of tested genotypes. This new gene and flanking markers should be useful in developing wheat cultivars with high level and possible durable resistance to stripe rust.

The German wheat cultivar Ibis has excellent adult plant resistance (APR) to stripe rust in Gansu, a hotspot for stripe rust in China. To elucidate the genetic basis of APR to stripe rust in Ibis, 237 F3 lines derived from the cross Ibis/Huixianhong were evaluated at Tianshui, Gansu, in the 2008-2009 and 2009-2010 cropping seasons, and at Chengdu, Sichuan Province, China, in the 2009-2010 cropping season. Inoculations were conducted with a mixture of several prevalent Pst races in both locations. Maximum disease severity (MDS) data showed a continuous distribution of response, indicating quantitative nature of resistance to stripe rust in Ibis. The broad-sense heritability of MDS was 0.75 based on the mean values averaged across three environments. A total of 723 simple sequence repeat (SSR) markers were used to map the QTL for APR by inclusive composite interval mapping (ICIM). QTLs mapping to chromosomes 2BS and 6BS, designated as QYr.caas-2BS.1 and QYr.caas-6BS.1, respectively, explained 4.1-40.7% of the phenotypic variance in MDS across environments. The major effect QTL QYr.caas-2BS.1, flanked by Xgwm148 and Xwmc360, was consistently detected at all three sites as well as the averaged data over three environments, accounting for 40.7, 24.2, 5.2 and 29.9% of phenotypic variance, respectively. The molecular markers closely linked to this QTL have potential for use in marker-assisted selection and gene pyramiding to improve the durability of stripe rust resistance in wheat breeding.