Postharvest ASM or Harpin Treatment Induce Resistance of Muskmelons Against Trichothecium roseum

Induced resistance was studied in muskmelons （cv. Yindi） inoculated Trichothecium roseum with postharvest 1,2,3- benzothiadiazole-7-carbothioic acid S-methyl ester （ASM） （100 mg L^-1） or harpin （50 mg L^-1） treatment. Both ASM and harpin significantly reduced lesion diameter in inoculated fruit. Lesion diameter was limited in the treated and untreated halves of the same fruit, indicating that the local and systemic resistance was induced. Inhibiting efficacy of elicitors lasted 7 and 5 days in the treated and untreated halves. The resistance increased by the chemicals was associated with the activation of peroxidase （POD） and chitinase （CHT）. The elicitors induced a significantly and progressively increasing activity of POD and CHT in the treated and untreated halves, and the activation lasted at least 5 days. The activities of POD isoenzymes increased in the treated fruit. However, no new enzyme band was found in the treated and untreated halves.

Induces Resistance Against Fusarium and Pink Rots by Acibenzolar-S-Methyl in Harvested Muskmelon (cv.Yindi)

Acibenzolar-S-methyl （ASM） is a chemical activator of systematic resistance in many plants. The effect of preharvest and postharvest application of ASM was evaluated for its ability to induce resistance in muskmelon fruit. The results indicated that 50 and 100 mg L^-1 ASM or 1 mL L^-1 imazalil at 1 week or 1 day before harvest were effective in reducing the lesion area with 100 mg L^-1 ASM the most effective. No treatment inhibited the infection rate. The postharvest results showed that 50 and 100 mg L^-1 ASM, and 0.1 mL L^-1 imazalil were effective in reducing the lesion area with 100 mg L^-1 ASM the most effective. No treatment inhibited the infection rate. There was a clear time-dependent response of the fruit to postharvest ASM treatment, in which treatments applied 1, 3, and 5 day before inoculation provided the best results. ASM did not demonstrate any fungicide effect in vitro and suppressed lesion area in treated muskmelons, indicating that disease resistance was induced. The protection of ASM was associated with the activation of peroxidase （POD） in treated muskmelons.

Control of Postharvest Fusarium Rot and Trichothecium Rot in Harvested Muskmelon (cv. Yindi) by Harpin

Preharvest and postharvest application of Harpin was evaluated for its ability to induce resistance in muskmelon fruit and control rots. Preharvest treatments were 30 mg L^-1, 60 mg L^-1 Harpin or 1 mg L^-1 Imazalil either I week or I day before harvest. The CK was untreated. Fruit were then inoculated with Fusarium semitectum or Trichothecium roseum 48 h after harvest, and stored at 23± 1℃, RH （relative humidity） 50-60% for 4 d. All treatments were effective in reducing the lesion area with 60 mg L^-1 Harpin the most effectively. No treatments inhibited infection rate. Postharvest treatment was fruit dips of 30 mg L i, 60 mg L^-1 Harpin, 0.1 mg L i Imazalil. Fruit were inoculated with F. semitectum or T. roseum 24, 72, 120 or 168 h after treatment, and stored at 23 ± 1℃, RH 50-60% for 4 days. All treatments were effective in reducing the lesion area with 60 mg L^-1 Harpin the most effectively. No treatments inhibited the infection rate. Postharvest Harpin treatment induced the peroxidase activity increase, peroxidase activity reached maximum after 8 d and the activation lasted at least 10 d.

Effects of thiamine on Trichothecium and Alternaria rots of muskmelon fruit and the possible mechanisms involved

The effects of thiamine against pink and black spot rots caused by Trichothecium roseum and Alternaria alternata and modulation on the metabolism of reactive oxygen species （ROS） and phenylpropanoid pathway were investigated in this paper. In vitro test indicated that thiamine significantly inhibited mycelia growth and spore germination of T. roseum and A. alternata. Thiamine at 100 mmol L-1 effectively inhibited lesion development of muskmelon fruit inoculated with T. roseum or A. alternata, enhanced production rate of O2; and H2O2 content, activities of catalase （CAT）, ascorbate peroxidase （APX） and glutathione reductase （GR） in muskmelon fruit. Thiamine also affect phenylpropanoid pathway in muskmelon fruit by increasing the activities of phenylalanine ammonia lyase （PAL） and peroxidase （POD）, the content of total phenolic compounds, flavonoids and lignin. These results suggest that the effects of thiamine on pink and black spot rots in muskmelon fruits are associated with its direct fungitoxic against the pathogens and the modulation of O2- and H2O2 production, elimi- nating enzymes and phenylpropanoid pathway.

Isolation and Identification of Main Fungal Pathogens in Muskmelon in Open Field of Hubei Province in Summer

Fungal diseases often occur seriously in muskmelon in open field of Hubei Province in summer, especially in continuous cropping pattern, resulting in great economic losses. In this study, the pathogens of main fungal diseases in muskmelon in open field of Hubei Province were isolated, and they were identified by morphological and molecular techniques. The results showed that muskmelon fusarium wilt is a major disease in muskmelon in open field of Hubei Province in summer, and its pathogen was confirmed to be Fusarium oxysporum. In future studies, one pair of specific primers would be designed to detect different pathogenic races of Fusarium oxysporum so as to accelerate the detection and to shorten the detection time,thereby proving guidance for actual production.

A Study of Oxalate-Induced Systemic Resistance of Muskmelon to Squash Mosaic Virus

By treatment with oxalate muskmelon cultivar “Wangwenxiang”, which is sensitive to squash mosaic virus (SqMV), develops systemic resistance to SqMV significantly. The challenge inoculation experiments indicate that the symptom of oxalate treated plants gets much slighter, the virus content is only 4% reduced to. The peroxidase activity increases by five times, three new isoperoxidases are induced, and lignin content increases by 82.9%. These results indicate that oxalate induces systemic resistance of muskmelon to SqMV while it induces increase of peroxidase activity, new isoperoxidases and content of lignin in the plants treated with oxalate.

Bacillus cereus X5 Enhanced Bio-Organic Fertilizers Effectively Control Root-Knot Nematodes(Meloidogyne sp.)

The efficacy of Bacillus cereus X5 as a potential biological control agent against root-knot nematodes was evaluated in vitro by examining second-stage juvenile mortality and egg hatching rate under addition of culture filtrate and in planta by application of bio-organic fertilizers enhanced with B. cereus X5, B. thuringiensis BTG, or Trichoderma harzianum SQR-T037 alone or together in greenhouse and field experiments. The biofumigation of the root-knot nematode-infested soil with organic materials (chicken manure, pig manure and rice straw) alone or in combination with B. cereus X5 was also conducted in greenhouse experiments. In laboratory, the filtrate of B. cereus X5 more effectively reduced egg hatching rates during the incubation period for 14 d and more effectively killed the second-stage juvenile during the incubation period of 24 h than that of B. thuringiensis BTG. The highest dry shoot weights for greenhouse tomatoes and field muskmelons were found in both the treatment consisting of the bio-organic fertilizer enhanced with the three biocontrol agents and the treatment consisting of the bio-organic fertilizer enhanced only with B. cereus X5. The two bio-organic fertilizers achieved better nematicidal effects than those enhanced only with B. thuringiensis BTG or T. harzianum SQR-T037. B. cereus X5 also enhanced effect of biofumigation, which resulted in increased plant biomass and reduced nematode counts in the roots and rhizosphere soil. Therefore, these results suggested that biological control of root-knot nematodes both in greenhouses and fields could be effectively achieved by using B. cereus X5 and agricultural wastes.

Oxalate-induced resistance of muskmelon to WMV-2

The treatment of muskmelon cultivar 'Wangwenxiang', which is sensitive to watermelon mosaic virus-2 (WMV-2), with oxalate increases systemic resistance of the cultivar to WMV-2 significantly. The challenge inoculation experiments indicate that the symptom of ox-alate-treated plant is much slighter than that of control plants and the virus content is only 4%