Potential value of small-molecule organic acids for the control of postharvest gray mold caused by Botrytis cinerea.

In the present study, a total of 21 natural or synthetic small-molecule organic acids were selected and determined for their activity against postharvest gray mold caused by B. cinerea. Overall, cuminic acid, which was extracted from the seed of Cuminum cyminum L, showed the most promising antifungal activity against B. cinerea both in vitro and in vivo. The study on action mechanism showed that cuminic acid could inhibit the development of sclerotia and the secretion of oxalic acid, destroy the cell membrane integrity, and down regulate the expression of several key genes involved in sclerotia development and pathogenicity of B. cinerea. Furthermore, cuminic acid could potentially reduce the degradation of TSS and TA content, while it had no significant effect on the weight loss, firmness, and VC content of apple and tomato. Importantly, cuminic acid could enhance the antioxidant enzyme activities of the fruits. All these results demonstrate the antifungal activity and highlight the great potential of cuminic acid as an alternative environmental-friendly agent for the control of postharvest gray mold both on fruits and vegetables.

Streptothricin-F Inhibition of FtsZ Function: A Promising Approach for Controlling Pseudomonas syringae pv. actinidiae.

Pseudomonas syringae pv. actinidiae (Psa) is a significant pathogenic bacterium affecting the kiwifruit industry. This study investigated the target sites of streptothricin-F (ST-F), produced by Streptomyces lavendulae gCLA4. The inhibition of ST-F on Psa was examined by the microscopic structural differences of Psa before and after treatment with ST-F, as well as the interaction between ST-F and cell division-related proteins. The results revealed filamentation of Psa after ST-F treatment, and fluorescence microscopy showed that ST-F inhibited the formation of the Z-ring composed of FtsZ protein. In vitro experiments and molecular docking demonstrated that ST-F can bind to FtsZ with a binding energy of 0.4 µM and inhibit FtsZ's GTP-dependent polymerization reaction. In addition, ST-F does not exert inhibitory effects on cell division in Psa strains overexpressing ftsZ. In conclusion, FtsZ is one of the target sites for ST-F inhibition of Psa, highlighting its potential as a therapeutic target for controlling Psa-induced kiwifruit bacterial canker.

Paenibacillus polymyxa YLC1: a promising antagonistic strain for biocontrol of Pseudomonas syringae pv. actinidiae, causing kiwifruit bacterial canker.

BACKGROUND: Kiwifruit bacterial canker (KBC) caused by Pseudomonas syringae pv. actinidiae (Psa) is the main limiting factor in the kiwifruit industry. This study aimed to identify bacterial strains with antagonistic activity against Psa, analyze antagonistically active substances and provide a new basis for the biological control of KBC. RESULTS: A total of 142 microorganisms were isolated from the rhizosphere soil of asymptomatic kiwifruit. Among them, an antagonistic bacterial strain was identified as Paenibacillus polymyxa YLC1 by 16S rRNA sequencing. KBC control by strain YLC1 (85.4%) was comparable to copper hydroxide treatment (81.8%) under laboratory conditions and field testing. Active substances of strain YLC1 were identified by genetic sequence analysis using antiSMASH. Six biosynthetic active compound gene clusters were identified as encoding ester peptide synthesis, such as polymyxins. An active fraction was purified and identified as polymyxin B1 using chromatography, hydrogen nuclear magnetic resonance (NMR), and liquid chromatography-mass spectrometry. In addition, polymyxin B1 also was found significantly to suppress the expression of T3SS-related genes, but did not affect the growth of Psa at low concentrations. CONCLUSION: In this study, a biocontrol strain P. polymyxa YLC1 obtained from kiwifruit rhizosphere soil exhibited excellent control effects on KBC in vitro and in field tests. Its active compound was identified as polymyxin B1, which inhibits a variety of pathogenic bacteria. We conclude that P. polymyxa YLC1 is a biocontrol strain with excellent prospects for development and application. © 2023 Society of Chemical Industry.

Postharvest sclerotinia rot control in carrot by the natural product hinokitiol and the potential mechanisms involved.

Sclerotinia rot infected by cosmopolitan fungi Sclerotinia sclerotiorum is a serious and destructive disease in carrot production, especially during their postharvest storage. Natural products with the advantages of environmentally friendly and safety have been widely concerned. This research estimated the impact of hinokitiol against S. sclerotiorum and on the quality of carrots. In vitro and in vivo tests demonstrated that hinokitiol had promising antifungal activities against both carbendazim-susceptible and -resistant isolates of S. sclerotiorum. Importantly, it effectively kept the quality and prolonged the shelf life of carrot by declining the loss of weight, ascorbic acid, carotenoid, and total phenolics content, preventing the formation of malondialdehyde, and enhancing the activities of antioxidant enzymes. Further study found that hinokitiol inhibited the formation of sclerotia by destroying the morphology and the integrality of cell membrane, reduced the pathogenicity by suppressing the synthesis of oxalic acid and exopolysaccharide, declined the activities of enzymes and the gene expression related to sclerotia development in S. sclerotiorum. These information evidenced the great potential of hinokitiol as a natural fresh-keeping agent for the management of postharvest decay infected by S. sclerotiorum.

Reproductive attributes and functional response of Anastatus japonicus on eggs of Antheraea pernyi, a factitious host.

BACKGROUND: Anastatus japonicus Ashmead (Hymenoptera: Eupelmidae) is a solitary egg endoparasitoid that has been studied for inundative biological control of Halyomorpha halys Stål (Hemiptera: Pentatomidae) in China. In this study, we assessed the reproductive attributes and functional response of Anastatus japonicus on a factitious host, Antheraea pernyi (Guérin-Méneville) (Lepidoptera: Anthelidae) at 25 ± 1 °C, 70 ± 5% relative humidity and 16 h:8 h light/dark photoperiod. RESULTS: The mean lifetime fecundity of Anastatus japonicus females was 404.3 progeny produced over an average oviposition period of 42.3 days. The sex ratio of adult progeny was slightly male biased (51.2%), whereas more female progeny were produced before day 20 of a female's life. Single 1-day-old mated Anastatus japonicus females exhibited a type II functional response to increasing host densities (1-50 eggs), with an inverse host density-dependent pattern of percent parasitism. The upper limit to the daily attack rate was estimated as 7.6 Antheraea pernyi eggs. Furthermore, mutual interference among Anastatus japonicus females occurred when increasing densities of parasitoids (1, 2, 4, 8, 16) were exposed to 30 host eggs. CONCLUSION: Laboratory functional response result revealed that individual Anastatus japonicus might be unable to respond effectively to increasing host density in the field, which could be compensated by releasing larger numbers of wasps. Strong mutual interference among foraging Anastatus japonicus females should be considered in any future inundative biological control programs for the sustainable management of Halyomorpha halys or other host insect pests. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Seasonal Abundance and Diversity of Egg Parasitoids of Halyomorpha halys in Kiwifruit Orchards in China.

To develop effective and targeted biocontrol tactics for the brown marmorated stink bug, Halyomorpha halys, in crop habitats, a good understanding is essential of the abundance and diversity of its parasitoids in different crop habitats in its native range. To obtain information on the egg parasitoid communities of H. halys in kiwifruit, surveys using sentinel egg masses were conducted in 2018 and 2019. These assessed the species composition of egg parasitoids of H. halys in green-fleshed 'Hayward' kiwifruit orchards, and quantified their season-long abundances in orchards under two different management systems. Parasitism was observed from June to August 2018 (mean parasitism: 48%) and from May to August 2019 (mean parasitism: 29%) across the experimental orchards. In total, five different parasitoid species were found across the two surveys seasons in the kiwifruit orchards, Trissolcus japonicus, T. cultratus, T. plautiae, Anastatus japonicus, and Acroclisoides sp., where T. japonicus and T. cultratus were the predominant species. Monthly T. japonicus abundance data had a unimodal distribution in 2018, peaking in July. There were two peaks (May-June and August) in the 2019 season. Overall, T. japonicus was significantly more abundant in the organic orchard than the conventionally managed orchard only in 2018, and its monthly abundance differed significantly in the two orchards in the two survey seasons. Results and their implications for future classical biological control for H. halys in kiwifruit are discussed.

A Newly Reported Parasitoid, Pentatomophaga latifascia (Diptera: Tachinidae), of Adult Halyomorpha halys in Beijing, China.

Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is a serious pest in agriculture and forests, as both adults and nymphs feed by piercing the surface of the plant and fruit tissues, causing damage. The eggs of H. halys are commonly attacked by parasitoids, however, the nymph and the adult are rarely attacked by natural enemies. We surveyed the parasitoids of adult H. halys by collecting samples from overwintering populations at three different locations and checked their body surfaces for the presence of tachinid eggs. Any host adults carrying tachinid eggs were reared in a cage for further species identification. We found that the eggs of Pentatomophaga latifascia (Villeneuve) (Diptera: Tachinidae) were laid on the surface of H. halys, and the hatched larvae penetrated the host body and fed internally to develop. The last larval instar emerged from the host to develop into pupae, killing the host in the process. According to the field survey, the average parasitism of H. halys by P. latifascia was 2.42%. The parasitoids of adult H. halys in their native range have so far been little studied and may provide a complementary component of egg parasitoids for biological control against H. halys in invaded areas.

Biology, Ecology, and Management of Erthesina fullo (Hemiptera: Pentatomidae): A Review.

The yellow spotted stink bug (YSSB), Erthesina fullo Thunberg, is one of the most widely distributed phytophagous insect pests in Asia. YSSB is highly polyphagous and in China it feeds on over 57 host plants in 29 families, including some economically important fruit crops such as kiwifruit, pear, peach, apple, and pomegranate. With a primarily r-selected life history strategy, reproductive diapause, aggregation behavior, wide host range, high dispersal capacity, and close association with human-modified ecosystems, YSSB is a potentially invasive species that poses significant biosecurity threats to other countries outside its native range. This review summarizes basic and applied knowledge on the biology, ecology, and management of YSSB in China, with specific emphasis on its life history, host range, damage and impacts on economically important horticulture crops, and integrated pest management (IPM) approaches. The insights from the Chinese literature on this pest will help the countries outside its native range to conduct appropriate biosecurity risk assessments, develop a sound surveillance program, and develop an emergency response plan before its invasion of new geographic areas.