Globally, white clover (Trifolium repens L.) is commonly infected by plant viruses.  It is grown at gardens, roadsides, and public areas as ornamental plants in northern China.  Some leaves present disease symptoms that are similar to those of virus infection.  However, to our knowledge, no records are available from China regarding white clover (Trifolium repens L.) virus co-infection.  To determine the viral species that infect white clover in China, plant samples with virus disease symptoms were collected and virion morphology and ultrastructure morphology of co-infected plants were observed by electron microscopy; viruses were detected by enzyme linked immunosorbent assay (ELISA) and reverse transcription PCR (RT-PCR).  Virus co-infection was studied by double antibody sandwich enzyme linked immunosorbent assay (DAS-ELISA) and real-time fluorescence quantitative PCR (RT-qPCR) after rub-inoculation of virus-free white clover planted in a growth chamber (25°C) with a photoperiod of 16 h, using single or several purified virions.  Results showed that there were six types of symptoms, including those of shrinking mosaic, shrinking and macular mosaic, severe mottle mosaic, yellow macular mosaic, shrinkage chlorisis, and ring plaque and ring stria.  The incidence rates for each symptom were 20.93, 1.48, 16.85, 59.07, 1.30, and 0.37%, respectively, based on the field investigation.  Two types of viral pathogens were identified as Alfalfa mosaic virus (AMV) and White clover mosaic virus (WCMV).  In mesophyll cells, virus particles with bacilliform virions formed aggregates and linear virions were bundle shaped.  The detection rate of AMV was 100% in white clover samples by DAS-ELISA and RT-PCR detection, whereas that of WCMV was 83.33%.  The co-infection rate was 83.33%.  The relative contents of AMV and WCMV were significantly increased by 5.897- and 3.515-fold upon co-infection, when compared to that with single virus infection.  We observed larger starch particles and fewer or collapsed chloroplast grana in co-infected plants; in addition, vacuoles were twisted and smaller, compared to those of healthy plants.  To our knowledge, this is the first report of co-infection by AMV and WCMV in white clover, which has caused severe mosaicism and ultrastructure lesions in co-infected plants in China.

Food safety issues constitute an international topic discussed by many scholars. Although there is an extensive body of literature on comparisons of food safety control practices across different governance structures, these studies have been conducted mainly in terms of qualitative and descriptive analysis. In addition, little attention has been given to family farms. This study addresses the food safety control practices adopted by firms with different governance structures in China. Food safety control is expressed by the following aspects, i.e., pollution-free, green, organic, and/or geographical indication products certification, establishment of production records, and pesticide residue testing. Three types of governance structures that engage in agricultural production are distinguished: farmer cooperatives, agricultural companies, and family farms. The food safety control practices of various governance structures are investigated based on a database that comprises 600 vegetable and fruit enterprises in Zhejiang, China. The results show that (1) pesticide residue testing is adopted by the most firms, followed by products certification, and production records are adopted by the fewest firms, and (2) agricultural companies adopt more food safety control practices than family farms, while farmer cooperatives adopt the fewest food safety control practices. Governance structure features of a cooperative in terms of ownership, decision-making, and income distribution are the main reasons for the low level of food safety control in the cooperative.

To evaluate the impact of climate change on maize production, it is critical to accurately measure the radiation use efficiency (RUE) for maize. In this study, we focused on three maize cultivars in Jilin Province, China: Zhengdan 958 (ZD958), Xianyu 335 (XY335), and Liangyu 99 (LY99).  Under the optimal growing conditions for high density (9 plants m^-2), we investigated the maize RUE during the vegetative and reproductive phases, and the entire growth period.  The results showed that the canopy light interception for maize peaked during anthesis.  After anthesis, maize plant biomass continued to accumulate.  Based on the absorbed photosynthetically active radiation (APAR), we calculated maize RUE.  During the entire growth period, maize RUE averaged 5.71 g MJ^-1 APAR among the three cultivars, with a high-to-low order of ZD958 (5.85 g MJ^-1 APAR)>XY335 (5.64 g MJ^-1 APAR)>LY99 (5.07 g MJ^-1 APAR).  Within the vegetative and reproductive growth periods, maize RUE averaged 6.85 and 5.64 g MJ^-1 APAR, respectively.  When utilizing maize models, such as APSIM, that depend on radiation use efficiency (RUE) to predict aboveground biomass accumulation, we observed that the current RUE value of 3.6 g MJ^-1 APAR is considerably lower than the measured value obtained under high-density optimal growing conditions.  Consequently, to derive the optimal potential yield for maize in such planting conditions, we recommend adjusting the RUE to a range of 5.07-5.85 g MJ^-1 APAR.