oming Xia

Inhibitory effect of lactoferrin against gray mould on tomato plants caused by Botrytis cinerea and possible mechanisms of action

Lactoferrin (LF), an 80 kDa iron binding glycoprotein, was effective in the control of gray mould caused by Botrytis cinerea on tomato. LF strongly inhibited spore germination and germ tube elongation of B. cinerea in vitro, especially at 100 mg/L. When viewed by fluorescence microscopy following staining with propidium iodide, the membrane integrity of B. cinerea conidia treated with LF (50 mg/L) decreased to 68% at 2 h. The leakage of carbohydrate and protein from mycelia increased as the dose of LF increased compared with the untreated controls. Furthermore, methane dicarboxylic aldehyde (MDA) content in B. cinerea spores exposed to LF increased markedly. The activities of superoxide dismutase and catalase in spores treated with LF were also 1.3, twice as high as those in the control at 6 h, whereas ATP content was 1.5 times lower. In planta assays demonstrated that LF exhibited significant curative effect (76.3%, 100 mg/L) against gray mould, compared with the preventive effect (52.6%, 100 mg/L). The mechanisms by which LF decreased gray mould decay of tomato plant may be directly related to the severe damage to the conidia plasma membrane and loss of cytoplasmic materials from the hyphae. These findings suggest that LF has potential as an antifungal agent to reduce the severity of gray mould of tomato plants.

Effect of abamectin on root‐knot nematodes and tomato yield

BACKGROUND Tomato growers in Shandong Province, China, commonly face heavy root-knot nematode infestations. Current methods of control include cadusafos and methyl bromide (MeBr), but alternative methods are required because of the high toxicity of these pesticides and the ecological risk of their use. Therefore, abamectin soil applications were evaluated for their potential to control soil nematodes in a series of laboratory tests, greenhouse pot experiments and field trials. RESULTS Laboratory tests showed that abamectin exhibited rapid knockdown of Meloidogyne incognita, with LC(50) and LC(90) values that were superior to those of cadusafos and averaged 7.06 and 21.81 mg L(-1). In the greenhouse pot experiment, soil applications of abamectin provided significant M. incognita control similar to that provided by cadusafos while maintaining excellent plant height and vigour. In the field trials, abamectin exhibited excellent control effects to nematodes while giving a higher tomato yield. There was a 19.3-39.0% yield increase from the various treatments compared with the control, and the best results were obtained from the highest dose of abamectin. CONCLUSION The results of this study demonstrated that abamectin has the potential to be used as an effective alternative to MeBr and cadusafos for nematode control in tomato production in Shandong Province.

Dissipation rate of thiacloprid and its control effect against Bemisia tabaci in greenhouse tomato after soil application

BACKGROUND Thiacloprid is a chloronicotinyl insecticide that is quite effective against sucking insects. In this study, when thiacloprid was applied at two different rates (normal rate 15 kg ha(-1) , double rate 30 kg ha(-1) ), the systemic distribution and residue of thiacloprid as well as its control effect against whitefly (Bemisia tabaci) were investigated in greenhouse tomato after soil application. RESULTS The results showed that thiacloprid was present in the tomato leaves until day 25, and then its amount was less than 0.005 mg kg(-1) and could not be detected. Thiacloprid residue in the tomato stems basically remained at a stable low level throughout the experimental period. Thiacloprid in soil had half-lives of 11.8 and 12.5 days for the normal treatment and the double treatment respectively. The control efficiency of whiteflies was about 90% from day 1 to day 10. This was followed by a slow decline, but efficiency was still higher than 50% until day 21. In addition, no significant differences were noted in the control effect of thiacloprid on whiteflies between the two different rates. CONCLUSION Soil application of thiacloprid at the normal rate can effectively control whiteflies, with high efficiency and long persistence.

Biology and life table studies of the oriental tobacco budworm, Helicoverpa assulta (Lepidoptera: Noctuidae), influenced by different larval diets

Development, survivorship, pupal weight, oviposition, and life table parameters of the oriental tobacco budworm, Helicoverpa assulta Guenée, were evaluated in the laboratory on an artificial diet, pepper (Capsicum frutescens L.), and tobacco (Nicotiana tobacum L.). We found that the average developmental time of immature stages was longest on tobacco (36.2 d), intermediate on pepper (34.4 d), and shortest on artificial diet (33.5 d). Immature survival from egg to pupa varied from 31% on tobacco, 43% on pepper, and 74% on artificial diet. Pupal weight ranged from 197.4 mg/pupa on tobacco, 233.1 mg/pupa on pepper and 253.4 mg/pupa on artificial diet. The average numbers of eggs laid by adults reared as larvae on the artificial diet, pepper, or tobacco were 614, 421 and 334 eggs/female, respectively. Numbers of remaining eggs in ovaries of the adult females reared as larvae on the artificial diet, pepper, or tobacco were 16, 26, and 42 eggs/female, respectively. The longevity of adult females developed from larvae reared on the three diets was not significantly different, whereas the longevity of male adults from the larvae reared on artificial diet was longer (16.8 d) than that for males reared on tobacco (13.8 d) and pepper (13.3 d). The intrinsic, finite, gross, and net rates of increase were highest for females reared as larvae on artificial diet, lowest for females emerging from larvae reared on tobacco, and intermediate for females emerging from larvae reared on pepper. Generation times and doubling time of H. assulta were shortest for larvae fed artificial diet, intermediate from larvae reared on pepper, and longest from larvae reared on tobacco. We concluded that the artificial diet was the most suitable larval diet of H. assulta followed by pepper, and tobacco.

Inhibitory effect of sulfated lentinan and lentinan against tobacco mosaic virus (TMV) in tobacco seedlings.

The antiviral activities of sulfated lentinan (sLNT) and lentinan (LNT) against tobacco mosaic virus (TMV) in tobacco seedlings and the underlying mechanism were investigated. Compared with LNT, sLNT showed significantly higher inhibitory effects on viral infection and TMV multiplication in a dose-dependent way, which might be due to its binding with TMV coat protein. In addition, both sLNT and LNT induced the transient production of H2O2 and expression of some defense-related genes (stilbene synthase, glucanase, acidic chitinase class IV, phenylalanine ammonia-lyase and 5-epi-aristolochene synthase) both locally and systemically. These results suggested that sLNT and LNT could control TMV incidence and the action mechanism might be associated with the affinity towards TMV coat protein and activation of some defense genes.

Transportation behaviour of fluopicolide and its control effect against Phytophthora capsici in greenhouse tomatoes after soil application.

BACKGROUND Fluopicolide, a novel benzamide fungicide, was registered for control of oomycete pathogens, including Phytophthora capsici. In this study, fluopicolide (5% SC) was applied in soil at rates of 1.5, 3 and 6 L ha(-1) [the normal (ND), double (DD) and quadruple dosages (QD) respectively] to investigate its transportation behaviour and control efficiency on tomato blight as a soil treatment agent. RESULTS The results showed that fluopicolide applied to soil could be absorbed by tomato roots and then transplanted to stems and leaves. It could exist in tomato roots for more than 30 days, and in leaves and stems until day 20 after application. The decline in fluopicolide in soil was in accordance with a first-order dynamics equation, with half-lives of 5.33, 4.75 and 5.42 days for the ND, DD and QD treatments respectively. The control efficiencies of fluopicolide were better with soil application than with spraying application, and the inhibition ratios were 93.02, 97.67 and 100 on day 21 for the ND, DD and QD treatments respectively. CONCLUSION Soil application of fluopicolide could control P. capsici in greenhouse tomatoes with high efficiency and long persistence.

Inhibitory effect of esterified lactoferin and lactoferin against tobacco mosaic virus (TMV) in tobacco seedlings

The inhibitory effects of esterified lactoferrin (ELF) and lactoferrin (LF) against tobacco mosaic virus (TMV) in tobacco seedlings and the underlying mechanism were investigated. ELF and LF significantly inhibited viral infection and TMV multiplication in tobacco plants. ELF showed a higher inhibition effect against TMV than LF treatment in a dose and time-dependent way. Moreover, ELF induced a higher increase in the levels of transcription of pathogenesis-related (PR) protein genes [acidic PRs (PR-1a, PR-2, PR-3, PR-5) and basic PR-1] and defense-related enzymes [phenylalanine ammonia lyase (PAL, EC 4.3.1.5), and 5-epi-aristolochene synthase (EAS, EC 2.5.1.35)] both locally and systemically, in correlation with the induction of resistance against tobacco mosaic virus. Furthermore, ELF also induced accumulation of salicylic acid, SA 2-O-β-D-glucoside and H2O2. These results suggested that ELF and LF could control TMV incidence and the mechanism might attribute to activate the expression of a number of defense genes.

Effects of Esterified Lactoferrin and Lactoferrin on Control of Postharvest Blue Mold of Apple Fruit and Their Possible Mechanisms of Action

The effects of esterified lactoferrin (ELF) and lactoferrin (LF) on blue mold caused by Penicillium expansum in apple fruit stored at 25 °C were investigated. Both ELF and LF provided an effective control and strongly inhibited spore germination and germ tube elongation of P. expansum in vitro. Assessment by propidium iodide staining combined with fluorescent microscopy revealed that the plasma membrane of P. expansum spores was damaged more seriously by ELF than by LF treatment, and the leakage of protein and sugar was higher from ELF-treated mycelia. Interestingly, ELF treatment induced a significant increase in the activities of chitinase, β-1,3-glucanase, and peroxidase in apple fruit, whereas both LF treatment and the control showed no obvious difference. These findings indicated that the effects of ELF on blue mold in apple fruit might be associated with the direct fungitoxic property against the pathogens and the elicitation of defense-related enzymes in fruit.