Salinity tolerance in rice is highly desirable to sustain production in areas rendered saline due to various reasons. It is a complex quantitative trait having different components, which can be dissected effectively by genome-wide association study (GWAS). Here, we implemented GWAS to identify loci controlling salinity tolerance in rice. A custom-designed array based on 6,000 single nucleotide polymorphisms (SNPs) in as many stress-responsive genes, distributed at an average physical interval of <100 kb on 12 rice chromosomes, was used to genotype 220 rice accessions using Infinium high-throughput assay. Genetic association was analysed with 12 different traits recorded on these accessions under field conditions at reproductive stage. We identified 20 SNPs (loci) significantly associated with Na+/K+ ratio, and 44 SNPs with other traits observed under stress condition. The loci identified for various salinity indices through GWAS explained 5–18% of the phenotypic variance. The region harbouring Saltol, a major quantitative trait loci (QTLs) on chromosome 1 in rice, which is known to control salinity tolerance at seedling stage, was detected as a major association with Na+/K+ ratio measured at reproductive stage in our study. In addition to Saltol, we also found GWAS peaks representing new QTLs on chromosomes 4, 6 and 7. The current association mapping panel contained mostly indica accessions that can serve as source of novel salt tolerance genes and alleles. The gene-based SNP array used in this study was found cost-effective and efficient in unveiling genomic regions/candidate genes regulating salinity stress tolerance in rice.

We build a distributed active measurement infrastructure to uncover the internals of the YouTube video delivery system. We deduce the key design features behind the YouTube video delivery system by collecting and analyzing a large amount of video playback logs, DNS mappings and latency data and by performing additional measurements to verify the findings. We find that the design of the YouTube video delivery system consists of three major components: a "flat" video id space, multiple DNS namespaces reflecting a multilayered logical organization of video servers, and a 3-tier physical cache hierarchy. Further, YouTube employs a set of sophisticated mechanisms to handle video delivery dynamics such as cache misses and load sharing among its globally distributed cache locations and datacenters.

Abstract-Effectively managing multiple data centers and their traffic dynamics pose many challenges to their operators, as little is known about the characteristics of inter-data center (D2D) traffic. In this paper we present a first study of D2D traffic characteristics using the anonymized NetFlow datasets collected at the border routers of five major Yahoo! data centers. Our contributions are mainly two-fold: i) we develop novel heuristics to infer the Yahoo! IP addresses and localize their locations from the anonymized NetFlow datasets, and ii) we study and analyze both D2D and client traffic characteristics and the correlations between these two types of traffic. Our study reveals that Yahoo! uses a hierarchical way of deploying data centers, with several satellite data centers distributed in other countries and backbone data centers distributed in US locations. For Yahoo! US data centers, we separate the client-triggered D2D traffic and background D2D traffic from the aggregate D2D traffic using port based correlation, and study their respective characteristics. Our findings shed light on the interplay of multiple data centers and their traffic dynamics within a large content provider, and provide insights to data center designers and operators as well as researchers.

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