Deoxyribonucleic
acid (DNA) methylation plays an important role
in fruit ripening and senescence. Here, the role of DNA methylation
of the CpG island of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 genes induced by heat treatment (37 °C) in
postharvest ripening of tomato fruit was studied. After heat treatment,
the firmness and vitamin C content showed higher levels, the loss
of aldehydes in volatile components was delayed, and the activities
of methylase and demethylase decreased in tomato fruit. Moreover,
in heat-treated fruit, significant changes in DNA methylation of SlACS10, LeCTR1, LeEIN3, LeERT10, and SlERF-A1 were induced,
the expression of LeERT10 and LeEIN3 was inhibited, the expression of SlERF-A1 was increased,
by which ethylene signal transmission might be suppressed and the
postharvest ripening of tomato fruit was delayed. The present study
provided valuable information for understanding the essential role
of DNA methylation in the postharvest ripening of tomato fruit.
IntroductionTea is one of the most widely consumed beverages around the world. Larvae of the moth, Ectropis obliqua Prout (Geometridae, Lepidoptera), are one of the most destructive insect pests of tea in China. E. obliqua is a polyphagus insect that is of increasing concern due to the development of populations resistant to certain chemical insecticides. Microbial biological control agents offer an environmentally friendly and effective means for insect control that can be compatible with “green” and organic farming practices.MethodsTo identify novel E. obliqua biological control agents, soil and inset cadaver samples were collected from tea growing regions in the Fujian province, China. Isolates were analyzed morphologically and via molecular characterization to identity them at the species level. Laboratory and greenhouse insect bioassays were used to determine the effectiveness of the isolates for E. obliqua control.ResultsEleven isolates corresponding to ten different species of Metarhizium were identified according to morphological and molecular analyses from soil and/or insect cadavers found on tea plants and/or in the surrounding soil sampled from eight different regions within the Fujian province, China. Four species of Metarhizium including M. clavatum, M. indigoticum, M. pemphigi, and M. phasmatodeae were documented for the first time in China, and the other species were identified as M. anisopliae, M. brunneum, M. lepidiotae, M. majus, M. pinghaense, and M. robertsii. Insect bioassays of the eleven isolates of Metarhizium revealed significant variation in the efficacy of each isolate to infect and kill E. obliqua. Metarhizium pingshaense (MaFZ-13) showed the highest virulence reaching a host target mortality rate of 93% in laboratory bioassays. The median lethal concentration (LC50) and median lethal time (LT50) values of M. pingshaense MaFZ-13 were 9.6 × 104 conidia/mL and 4.8 days, respectively. Greenhouse experiments and a time-dose-mortality (TDM) models were used to further evaluate and confirm the fungal pathogenic potential of M. pingshaense MaFZ-13 against E. obliqua larvae.DiscussionIsolation of indigenous microbial biological control agents targeting specific pests is an effective approach for collecting resources that can be exploited for pest control with lowered obstacles to approval and commercialization. Our data show the presence of four different previously unreported Metarhizium species in China. Bioassays of the eleven different Metarhizium strains isolated revealed that each could infect and kill E. obliqua to different degrees with the newly isolated M. pingshaense MaFZ-13 strain representing a particularly highly virulent isolate potentially applicable for the control of E. obliqua larvae.
Postharvest green mould caused by Penicillium digitatum is one of the most important diseases in citrus fruit, which leads to fruit decay, green mould accumulation and huge economic losses. The inhibitory effect of 1‐methylcyclopropene (1‐MCP) on the postharvest green mould of citrus fruit was investigated. In vivo experiments showed that 1‐MCP significantly suppressed the green mould and the decay incidence in postharvest citrus fruit, and inhibited the mycelial growth and spore germination of P. digitatum. In vitro experiments, the lower integrity of plasma membrane, the higher content of reactive oxygen species (ROS) in spores and the higher content of malondialdehyde (MDA) in mycelium were detected in the 1‐MCP‐treated P. digitatum, showed that 1‐MCP increased oxidative damage and harmed the membrane integrity of P. digitatum. This study demonstrated that 1‐MCP inhibited postharvest green mould of citrus fruit by damaging the membrane integrity and influencing the growth of P. digitatum.
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