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Heterosis and polyploidy have an overwhelming influence on plant evolution. Recently, polyploid rice hybrids have been used to breed new rice varieties because they combine the advantages of both heterosis and polyploidy. In this study, we generated six rice lines: autotetraploid rice hybrids and their autotetraploid parents, diploid donors, and hybrids of the diploid donors. To investigate the molecular mechanism controlling the effects of both hybridization and polyploidization, we performed bisulfite and RNA sequencing on young panicles at the pollen meiosis stage to compare the DNA metabolomes and transcriptomes among the six rice lines. The hybrids lines were hypermethylated compared to their corresponding parents and the autotetraploid lines showed globally increased DNA methylation of their transposable elements compared to the diploid donors. The alteration in DNA methylation level corresponded to the differential gene expressions among the rice genotypes, suggesting that methylation changes induced by polyploidization and hybridization may affect gene expression. Groups of gene candidates were identified that may be associated with heterosis and polyploidy. Our results provide DNA information that can be used to investigate epigenetic modification during heterosis and polyploidy in rice. [ABSTRACT FROM AUTHOR]

Variety identification plays an important role in protecting the intellectual property of varieties, ensuring seed quality, and encouraging breeding innovation. Currently, morphological evaluation in the field, such as distinctness, uniformity, and stability (DUS) testing, and DNA fingerprinting in the laboratory using molecular markers are two dominant methods used for variety identification. Few studies have compared the results of these approaches, and the relationship between the two methods is obscure. In this study, 134 dominant cucumber varieties were evaluated using 50 DUS testing traits and genotyped by 40 single nucleotide polymorphisms (SNPs). The 40 SNPs were developed in our previous study and are well suited for variety identification. In the DUS testing, significant positive or negative correlations among 50 DUS traits were observed, and 20 core traits, including 15 fruit traits, were further selected to increase field inspection efficiency. This suggested that fruit shape plays an important role in variety identification. The ratio of fruit length/diameter was the most important trait, explaining 9.2% of the phenotypic variation. In the DNA fingerprinting test, the 40 SNPs were highly polymorphic and could distinguish all of the 134 cucumber varieties, and 14 core SNPs were selected to improve the identification rate. Interestingly, the population structure analysis of 134 cucumber varieties by phenotypic data in the DUS test was in accordance with the genotypic data from the DNA fingerprinting, indicating that all varieties could be divided into the same four subgroups: European type, North China type, South China type, and hybrids of the North China and South China types. Moreover, linear correlativity of distinguishment for each pair of varieties was observed between the DUS test and the DNA fingerprinting. These results indicated that these two methods have good application in future research, especially for the scaled-up analysis of hundreds of varieties. [ABSTRACT FROM AUTHOR]

A systematic investigation on the mechanism of dynamic liquid dispersing process via theoretical and experimental approach is presented. The experiments include weak and strong constrained scenarios using the high-speed camera technique and the flash X-ray radiography technique. Based on dynamic analysis, one-dimensional characteristics analysis and some numerical simulations on the propagating processes of blast waves before the container shell rupturing, further and detailed analyses of the experimental results are presented. The effects of the liquid viscosity on the dynamic dispersing flow are also analyzed, and the spall fracture mechanism is explored. Thus, the dominating forces determining the dispersing liquid flow are revealed, that is, the stretching and shearing action due to the interaction of two reflecting rarefaction waves in opposite propagating directions. The influence of container shell strength on the dispersing liquid flow is also investigated, and the characters of cavitation layered in liquid before shell rupturing are uncovered. Results revealed that different shell material results in different cavitating layers. Then the different cavitating layers drive the different dynamic liquid dispersing process coming into being. The metastable liquid states caused by pressure drop and cavitation generation are discussed. [ABSTRACT FROM AUTHOR]