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The objective of this study is to investigate a viable and effective method for artificially breeding the mandarin fish (Siniperca chuatsi) in the out-of-breeding season. The mature development of the female mandarin fish's gonad was induced through precise control of water temperature. Measurements were taken during the temperature control period, including body weight, body height, ovulation rate, relative fecundity and gonadosomatic index (GSI). Serum hormone levels were assessed, and histological sections of gonadal tissues were tracked. Subsequently, a series of experiments were conducted to establish the optimal protocol for hormone-induced ovulation and artificial fertilization. The findings revealed that manipulation and elevation of the aquaculture water body temperature could effectively induce gonad development and maturation in mandarin fish. In the high temperature group (HT, water temperature maintained at 25 ± 1 ℃), 81.25 % of the experimental fish reached maturity within 20 days. Subsequent hormone injection resulted in successful ovulation, normal fertilization, and subsequent incubation of viable young fish. Furthermore, the outcomes of the ovulation test using hormones demonstrated that the pairing of luteinizing hormone releasing hormone (LHRH-A2) and domperidone (DOM) proved highly effective in inducing ovulation in mature mandarin fish in the out-of-breeding season. The ideal dosage for a single injection of this combined hormone was determined to be 6 μg LHRH-A2 and 4 mg DOM / kg of body weight. Employing this optimal hormone dosage resulted in a fertilization rate of 83.23 %, a ovulation rate of 100 %, a relative fecundity of 93.40 ± 17.59 103 / kg and a hatching rate of 88.85 %. The anticipated outcome of these studies is to enhance the artificial breeding techniques for mandarin fish in commercial aquaculture, allowing for year-round production of fertilized eggs.

Commercialized genetically modified (GM) papaya cultivars have protected papaya from the devastating disease caused by papaya ringspot virus (PRSV). However, papaya leaf distortion mosaic virus (PLDMV), which causes similar infection symptoms but is serologically distinct from PRSV, was found to be a competitive threat to the papaya industry. Our study surveyed the occurrence of PRSV and PLDMV, as well as the transgenic markers of the 35S promoter from cauliflower mosaic virus and the neomycin phosphotransferase II gene in feral papaya plants, which were found frequently growing outside of cultivated papaya fields on Hainan Island. In total, 123 feral papayas, comprising 62 (50.4%) GM plants and 61 (49.6%) non-GM ones, were sampled. Among them, 23 (18.7%) were positive for PRSV, 49 (39.8%) were positive for PLDMV (including five plants co-infected by PRSV and PLDMV), and 56 (45.5%) were free of either virus. In traditional papaya-growing regions, we detected fewer PRSV-infected plants (2 in 33, 6%) than in other regions (21 in 90, 23%). However, overall, whether plants were transgenic or not made no difference to PRSV incidence (P = 0.230), with 9 PRSV-infected plants among 62 GM papayas and 14 among 61 non-GM papayas. Phylogenetic and genetic differentiation analysis showed a clear correlation between PRSV and PLDMV populations and their geographic origins. Negative selection was estimated for the selected gene regions of both viruses. Notably, PLDMV has deviated from neutral evolution and experienced population expansion, exhibiting increased genetic diversity, and is becoming the predominant threat to papaya in Hainan. [ABSTRACT FROM AUTHOR]