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The development of the horticultural industry is largely limited by disease and excessive pesticide application. MicroRNAs constitute a major portion of the transcriptomes of eukaryotes. Various microRNAs have been recognized as important regulators of the expression of genes involved in essential biological processes throughout the whole life cycle of plants. Recently, small RNA sequencing has been applied to study gene regulation in horticultural plants. In this review, we summarize the current understanding of the biogenesis and contributions of microRNAs in horticultural plant disease resistance. These microRNAs may potentially be used as genetic resources for improving disease resistance and for molecular breeding. The challenges in understanding horticultural plant microRNA biology and the possibilities to make better use of these horticultural plant gene resources in the future are discussed in this review.

The effects of zirconia and yttrium oxide addition on microstructure, bulk density, microhardness, flexural strength, and wear resistance of high alumina ceramics (>97 wt% Al 2 O 3 , MSA ceramics) composed of MgO-SiO 2 -Al 2 O 3 system have been investigated. The results show that the addition of zirconia makes the mechanical properties and wear properties of ceramics composed of MgO-SiO 2 -Al 2 O 3 -ZrO 2 (MSAZ ceramics) system have been greatly improved compared with MSA ceramics. In addition, the ceramics composed of MgO-SiO 2 -Al 2 O 3 -ZrO 2 -Y 2 O 3 (MSAZY ceramics) system have better mechanical properties and wear properties than MSAZ ceramics. With the contents of zirconia and yttrium oxide increase, the bulk density, microhardness, and flexural strength of MSAZ and MSAZY ceramics increased at first and then decreased. However, the wear rate shows the opposite. When 0.4 wt% ZrO 2 and 0.6 wt% Y 2 O 3 were added to the matrix, the wear rate of MSAZY ceramics reached a minimum of 0.042%, and the wear resistance was improved by about 73.8% compared with MSA ceramics with a wear rate of 0.16%. In addition, the optimum additions of zirconia and yttria are 0.4% and 0.6%, respectively. K E Y W O R D S ceramic matrix composites, mechanical properties, MgO-SiO 2 -Al 2 O 3 system, wear rate

Yes. We contrast the impacts of COVID-19 shocks and medical and political countermeasures in an otherwise standard model of financial market return determinants. During the pandemic, fears about COVID-19 can replace the economic sentiment to have a lasting negative impact on the stock market, especially in the first wave of the virus spreading. Medical research and government policies contribute to the stimulations of financial markets; however, efficient vaccines, when not developed, tend to negatively impact future stock returns and exacerbate the negative influence of COVID-19 sentiment on the stock market. Instead, such situations can be eased once medical research becomes advanced, helping the reconstruction of investor confidence. Public attention to the political support promoting economic and financial recovery has a positive impact on stock market returns and mitigates the shock of COVID-19 sentiment on the stock market.