Analysis of Genomic Genetic Diversity of Cucurbit Aphidborne Yellows Virus

[Objectives]This study was conducted to investigate the molecular characteristics,genetic structure and evolutionary mechanism of cucurbit aphid-borne yellows virus(CABYV),which is of great significance for clarifying the epidemic laws of the disease in the field and formulating long-term sustainable control strategies.[Methods]120 melon leaves suspected to be infected with CABYV were randomly collected from Aksu City,Xinjiang.RT-PCR was used to detect the virus.MEGA 7.0 was used to construct a phylogenetic tree.DnaSP v5.10 was used to analyze the genetic diversity among different sequences,and RDP v.4.31 software was used to analyze possible recombination events of CABYV sequence.[Results]The detection rate of CABYV was 31.67%.A new CABYV-2 was isolated,sequenced and cloned from these positive samples.The length of the genome is 5497 bp,encoding six open reading frames.Compared with 23 CABYV strains isolated from different countries in NCBI database,CABYV-2 shared the highest homology with KR231942.1 and the lowest homology with JF939812.1.The results of evolutionary tree analysis showed that the 24 isolates were divided into two branches due to different geographical factors,including CABYV-2 and KR2319421,which were clustered together and belonged to branch 1.The results of genetic diversity and neutrality tests showed that CABYV was highly variable and the population was expanding.The results of recombination analysis showed that there were two recombinants,EU636992.1 and KR231949.1,which exacerbated the variation of CABYV.[Conclusions]The CABYV isolate from Aksu City,Xinjiang had the closest relationship with the Korean isolate KR231942.1,and the farthest relationship with the isolates from European countries.There were large genetic differences between the isolates of branch 1 and branch 2,and the recombination of CABYV in different hosts aggravated the variation of CABYV.Recombination and negative selection may be important reasons for the genetic variation of CABYV.

Optimizing B^(+)-tree for hybrid memory with in-node hotspot cache and eADR awareness

he advance in Non-Volatile Memory(NVM)has changed the traditional DRAM-onlymemorysystem.Compared to DRAM,NVM has the advantages of nonvolatility and large capacity.However,as the read/write speed of NVM is still lower than that of DRAM,building DRAM/NVM-based hybrid memory systems is a feasible way of adding NVM into the current computer architecture.This paper aims to optimize the well-known B^(+)-tree for hybrid memory.The novelty of this study is two-fold.First,we observed that the space utilization of internal nodes in B^(+)-tree is generally below 70%.Inspired by this observation,we propose to maintain hot keys in the free space within internal nodes,yielding a new index named HATree(Hotness-Aware Tree).The new idea of HATree is to use the unused space of the parent of leaf nodes(PLNs)as the hotspot data cache.Thus,no extra space is needed,and the in-node hotspot cache can efficiently improve query performance.Second,to further improve the update performance of HATree,we propose to utilize the eADR technology supported by the third-generation Intel Xeon Scalable Processors to enhance HATree with instant log persistence,which results in the new HATree-Log structure.We conduct extensive experiments on real hybrid memory architecture involving DRAM and Intel Optane Persistent Memory to evaluate the performance of HATree and HATree-Log.Three state-of-the-art indices for hybrid memory,namely NBTree,LBTree,and FPTree,are included in the experiments,and the results suggest the efficiency of HATree and HATree-Log.