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The banning of synthetic fungicides for postharvest use on fruits in Canada has prompted a search for alternative control strategies for postharvest brown rot caused by Monilinia fructicola (Wint.) Honey on sweet cherry (Prunus avium L.). Thymol and carvacrol were the two most potent fungicides among the monoterpenoids tested. The brown rot incidences of M. fructicola-inoculated cherry dipped in 1000 μg·mL-1 thymol and carvacrol were 24% and 23%, respectively, compared with 81% for the control. The effects of thymol and carvacrol were not significantly enhanced by the addition of CaCl2 or CaB'y®, a foliar calcium fertilizer. Decco® 282 significantly reduced the activity of thymol. Methyl jasmonate, an elicitor of plant defense mechanisms, did not reduce brown rot by itself, and did not increase the efficacy of thymol and carvacrol when used as an additive in dipping or fumigation experiments. Thymol and carvacrol caused stem browning of cherry fruits in the fumigation experiment, however, 69% and 73%, respectively, of the browning was prevented when methyl jasmonate was used as a co-fumigant. Chemical names used: 5-methyl-2-(1-methylethyl)phenol (thymol); 2-methyl-5-(1-methylethyl)phenol (carvacrol); methyl 3-oxo-2-(2-pentenyl)cyclopentane acetate (methyl jasmonate).
Tomato (Solanum lycopersicum) fruit ripening is a complex genetic trait correlating with notable fruit phenotypic, physiologic, and biochemical changes. Transcription factors (TFs) play crucial roles during this process. LeHB-1, an HD-zip homeobox protein, is a ripening-related TF and acts as an important regulator of fruit ripening. However, the detailed biochemical and molecular basis of LeHB-1 on tomato fruit ripening is unclear. In the current study, the biologic functions of LeHB-1 were determined by a potato virus X (PVX)-mediated gene-silencing approach. The results indicate that PVX-induced LeHB-1 silencing in tomato could decrease pigment accumulation and delay fruit ripening. Compared with controls, nonripening flesh retains a greater pH value and a lesser anthocyanin content. By evaluating expression levels of genes related to tomato fruit ripening, we inferred that LeHB-1 located at the downstream of LeMADS-RIN-mediated regulatory network. In addition, LeHB-1 silencing mainly disturbed phytoene desaturation and isomerization, and led to a decrease in trans-lycopene accumulation, but did not influence flavonoid biosynthesis directly in tomato fruit. The findings provide a theoretical foundation for illustrating the biologic functions of LeHB-1 in tomato fruit ripening and quality.
The interaction between potassium (K) and magnesium (Mg) in plants has been intensively studied. However, the responses of different tomato (Solanum lycopersicum L.) cultivars to high K levels at low temperatures remained unclear. Herein, a complete randomized hydroponic experiment was conducted to evaluate the effects of temperature (25 °C day/18 °C night vs. 15 °C day/8 °C night) and K concentrations (156 mg·L−1 vs. 468 mg·L−1) on the growth and Mg nutrition of tomato cultivars Gailiangmaofen (MF) and Jinpeng No. 1 (JP). Compared with the control temperature (25 °C day/18 °C night), the low temperature decreased total biomass, shoot biomass, and Mg uptake in shoot by 17.3%, 24.1%, and 11.8%, respectively; however, the root/shoot ratio was increased. High K had no significant effect on plant growth or biomass compared with the control K concentration (156 mg·L−1); however, Mg concentrations and uptake in shoot were significantly lower under high-K treatment. Significant difference was observed for K uptake, but not for Mg uptake, between the two cultivars. There was no significant interaction between temperature and high K on Mg uptake of tomato, so a combined stress of low temperature and high K further inhibited Mg uptake and transport. Low temperature and high K increased the risk of Mg deficiency in tomato.