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Low-impact development (LID) is generally regarded as an effective solution for urban stormwater management. However, the effects of LID on storm flooding on an urban drainage systems scale have not been fully understood under different rainfall characteristics. In this paper, using a high-density residential catchment in China as a case study, the PCSWMM model is applied to simulate the control effects of seven LID land layout scenarios on water quantity and quality of rainfall runoff under different rainfall return periods, durations, and locations of peak rainfall intensity. The simulations indicated the following results: (1) All seven LID scenarios are more effective in flood control during smaller rainfall return periods and longer rainfall duration storms, and the influence of locations of peak rainfall intensity on the rainfall runoff is not obvious. (2) Permeable pavement is the best choice in single LID measures, and the combination of permeable pavement, vegetative swale, and a green roof is the best choice among combined LID layouts. This paper gives insight into the performance of LID designs under different rainfall characteristics, which is essential for effective sponge city construction.
Barley yellow dwarf virus (BYDV) can cause significant losses of wheat worldwide. The long arm segment of Thinopyrum intermedium chromosome 7Ai#1 carrying the BYDV resistance gene Bdv2 was translocated to the distal region of the long arm of wheat chromosome 7D in translocation line Yw642. In this study, 40 wheat EST sequences located in the distal region of 7DL were explored to identify specific PCR markers for the Bdv2 region on the basis of the homoeologous relationship between wheat chromosome 7D and Th.intermedium chromosome 7Ai#1. Our results revealed 8 novel EST-PCR markers specific to the Bdv2 region, including 5 EST-STS markers of BE404744, BE498985, BE591497, BG606695 and BQ161842, and 3 EST-SSCP markers of BE404953, BG312663 and BE498985. These EST-PCR markers could distinguish Bdv2 from another BYDV-resistance gene located on Th.intermedium chromosome 2Ai-2. These specific bands for the Bdv2 region were further cloned and sequenced. The sequencing analysis indicated that the specific sequences for the Bdv2 region were highly homologous with the original wheat EST sequences that were used to design primers, and encode respectively a protein kinase, P450, centrin, transducin, and a hypothetical protein. This study created a starting point for eventual cloning of the Bdv2 gene and understanding the defense mechanism.
Powdery mildew disease caused by Blumeria graminis f. sp. tritici (Bgt) is an economically important disease in wheat worldwide. The identification of germplasms resistant to the disease can not only facilitate the breeding of resistant cultivars, but can also broaden the diversity of resistance genes. The Mexican M53 is a synthetic hexaploid wheat line developed at the International Maize and Wheat Improvement Center (CIMMYT) from the cross between Triticum durum and Aegilops tauschii249. Infection of M53 with 15 different pathogen races revealed that the resistance in M53 was race-dependent and effective against the majority of the tested Bgt races, including the race 15 predominant in the Beijing wheat growing area. Inoculation of the parents of M53 with the race 15 demonstrated that M53 and Ae. tauschii249 were resistant, whereas T. durum was susceptible. The inoculation of three segregating F2 populations developed from the crosses between M53 and three susceptible Chinese wheat cultivars with the race 15 showed that the resistant gene in M53 segregated in a single dominant manner. Amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers were used to map the gene in a segregating F2 population consisting of 213 lines developed from the cross Wan7107 × M53. Two closely linked AFLP markers, Apm109 and Apm161, were identified to flank the gene with genetic distances of 1.0 cM and 3.0 cM, respectively. The recognized gene was assigned to the long arm of chromosome 5D as determined by three linked SSR markers, Xwmc289b, Xgwm583, and Xgwm292, and by the physical mapping of Apm109 using Chinese Spring nullisomic–tetrasomic and ditelosomic stocks. The resistance gene identified in M53, temporarily designated as Pm-M53, could be used in local wheat-breeding programs to improve powdery mildew resistance.
Braya humilis (Brassicaceae) is a widely distributed plant in arid and semi-arid regions of northern Asia. This plant is well adapted to extremely arid conditions and is a promising candidate species to discover novel drought tolerance strategies. However, not much information about the mechanism(s) mediating drought resistance in this species is currently available. Therefore, the present study aimed to characterize the physiological traits and expression patterns of a polyethylene glycol (PEG)-responsive gene in B. humilis responding to different levels of osmotic stress induced by PEG-6000. Several important physiological parameters were examined, including the levels of relative water content, soluble protein, malondialdehyde, and antioxidant enzyme activity. A tolerance threshold between 20 and 30% PEG-6000 was identified for B. humilis. The water status and oxidative damage below this threshold were maintained at a relatively constant level during the 12 h of treatment. However, once the threshold was exceeded, the water status and oxidative damage were obviously affected after treatment for 4 h. The soluble protein results suggest that B. humilis maintains a vigorous resistance to osmotic stress and that it may play a greater role in osmotic regulation at late stages of stress. Moreover, superoxide dismutase and catalase may be important at preventing oxidative damage in plants at early stages of stress, while peroxidase may be more involved in some biological processes that resist osmotic stress at the late stage, especially in severely damaged plants. Furthermore, a PEG-responsive gene, BhCIPK12, was identified by differential display reverse transcription-polymerase chain reaction (PCR), cloned, and characterized by quantitative real-time PCR. We hypothesized that this gene may play an important role in mediating osmotic stress or drought resistance in plants. Altogether, these results provide valuable insights into the mechanism(s) mediating drought tolerance in B. humilis.
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