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Genomic simple sequence repeat (SSR) markers were used to fingerprint and determine genetic similarity (GS) of the watermelon breeding lines, as well as the purity of their hybrid derivatives. Cluster analysis and Jaccard’s distance coefficients using the unweighted pair group method with arithmetic mean (UPGMA) have classified these lines into three major groups. Notwithstanding, the genetic background of these lines is narrow as revealed by the restricted GS coefficients. Fifty-five sets of SSR markers were employed in this study. Fourteen of these markers were polymorphic between the breeding lines and were used for assessing hybrid purity. Cross-checking assay validated nine SSR markers as informative SSR markers for purity detection of these hybrids. To confirm the accuracy and efficiency of these markers, their derived PCR products were further sequenced, and ClSSR09643, ClSSR18153 and ClSSR01623 were selected as high-efficiency SSR markers. Interestingly, SSR markers ClSSR09643 and ClSSR18153 were broadly applied for purity detection of more than two different hybrids, while SSR marker ClSSR01623 behaved as a specific marker for purity detection in this study. Genetic purity of six commercial watermelon hybrids was definitely evaluated using these SSR markers. Genetic purity of all tested hybrids exceeded 96% while the field purity was above 98%. Genetic purity test was an emergency for identifying off-types and selfed female in a lot of hybrid seeds. Here, we elucidated the potential of nine SSR markers including three with higher breeding selection efficiency. We recommended them to seed company for purity improvement of watermelon commercial hybrid varieties.

Metasequoia glyptostroboides is an endangered relict plant native to China that has been widely introduced into many countries and areas around the world. However, its seeds germinate at a very low percentage. Consequently, population regeneration by seed is low under natural conditions, which probably contributes to the endangered status of this plant species. The present study aimed to describe the aging mechanism of M. glyptostroboides seeds. Our objective was to elucidate causes of the low germination rate in an effort to enhance potential for conservation of the species. We used germination tests, relative electrical conductivity and malondialdehyde content determination, ultrastructural observation of embryo cells, and analysis of superoxide dismutase, catalase, ascorbate peroxidase, and dehydroascorbate reductase activities during accelerated aging treatment. We found that M. glyptostroboides seeds have a low level of vigor and poor ability to maintain vigor, which is probably associated with the inefficiency of its enzymatic antioxidative system.

Insertion and Deletion (InDel) are common features in genomes and are associated with genetic variation. The whole-genome re-sequencing data from two parents (X1 and X2) of the elite cucumber (Cucumis sativus) hybrid variety Lvmei No.1 was used for genome-wide InDel polymorphisms analysis. Obtained sequence reads were mapped to the genome reference sequence of Chinese fresh market type inbred line ‘9930’ and gaps conforming to InDel were pinpointed. Further, the level of cross-parents polymorphism among five pairs of cucumber breeding parents and their corresponding hybrid varieties were used for evaluating hybrid seeds purity test efficiency of InDel markers. A panel of 48 cucumber breeding lines was utilized for PCR amplification versatility and phylogenetic analysis of these markers. In total, 10,470 candidate InDel markers were identified for X1 and X2. Among these, 385 markers with more than 30 nucleotide difference were arbitrary chosen. These markers were selected for experimental resolvability through electrophoresis on an Agarose gel. Two hundred and eleven (211) accounting for 54.81% of markers could be validated as single and clear polymorphic pattern while 174 (45.19%) showed unclear or monomorphic genetic bands between X1 and X2. Cross-parents polymorphism evaluation recorded 68 (32.23%) of these markers, which were designated as cross-parents transferable (CPT) InDel markers. Interestingly, the marker InDel114 presented experimental transferability between cucumber and melon. A panel of 48 cucumber breeding lines including parents of Lvmei No. 1 subjected to PCR amplification versatility using CPT InDel markers successfully clustered them into fruit and common cucumber varieties based on phylogenetic analysis. It is worth noting that 16 of these markers were predominately associated to enzymatic activities in cucumber. These agarose-based InDel markers could constitute a valuable resource for hybrid seeds purity testing, germplasm classification and marker-assisted breeding in cucumber.

To solve the time-frequency aliasing problem of various radar signals in a complex electromagnetic environment, a radar signal separation method based on capsule neural network is proposed. In this paper, the capsule neural network (Caps Net) is briefly introduced as preliminary. In the proposed method, the radar signal is firstly preprocessed to build a deep feature space, then pulses are separated based on a Density-Based Spatial Clustering of Applications with Noise (DBSCAN), and used the capsule neural network to separate the aliasing points in the cluster. The performance of the proposed method is verified by numerical simulations. The results show that it can achieve an effective separation of 8 mixed radar signals. Compared with traditional method, the accuracy is significantly improved, and the recognition probability is over 95% with $\text{SNR}=15\text{dB}$ .

High-speed space vehicles realize interconnection, coordinated operations and precise strikes through Flying Ad hoc Network (FANET), which has the characteristics of high-speed node, highly dynamic network topology, and multiple priority tasks guarantee requirements. First, a five-layer protocol architecture networking scheme suitable for FANET is proposed, which adopts Statistical Priority-based Multiple Access (SPMA) as data link layer multiple access protocol. Then, SPMA algorithm flow is designed, and three key algorithms, namely, channel occupancy statistics algorithm, priority threshold algorithm and back off time algorithm are briefly analyzed and feasible solutions are given. Finally, simulation modeling of FANET basing on SPMA is conducted on OPNET platform. Through theoretical analysis and simulation experiments, it can be proved that SPMA protocol designed in this paper can realize multiple priority differentiated services, ensure low latency and high reliability of high-priority packets, and meet the QoS requirements of FANET. Moreover, compared to the traditional CSMA/CA protocol, the SPMA protocol has better performance in all aspects.

As an important carrier of battlefield information acquisition and transmission, electromagnetic spectrum space has become the key for future battlefield to control information superiority. In order to achieve the mastery of information in the future electromagnetic spectrum space, covert communication has become a research hotspot. This paper explores the covert communication technology for complex electromagnetic environment. It introduces the main research directions in the field of covert communication and typical covert communication systems at home and abroad. In this paper, the multi-dimensional characteristics of signal such as time domain, frequency domain and code domain are used. The modulation technology is combined with the statistical characteristics of amplitude, frequency and phase. Then the covert communication system based on multi-domain integration for complex electromagnetic environment is established, so as to enhance the ability of information covert transmission. Furthermore, a compound dimension information authentication method is established to improve the anti cracking and anti intrusion level of the covert communication system. Finally, the main performance of the new scheme is verified by simulation, which lays a technical foundation for the subsequent application of the algorithm.