Sodium Silicate Reduces Postharvest Decay on Hami Melons: Induced Resistance and Fungistatic Effects

Abstract

The effect of sodium silicate (Si) for control of decay was tested in Hami melons (Cucumis melo L. var. inodorus Jacq.). Si significantly inhibited mycelial growth of Alternaria alternata, Fusarium semitectum, and Trichothecium roseum in vitro. Si at 100 mM was more effective than Si at 25 or 50 mM at controlling the diseases caused by the three pathogens, whereas Si at 200 mM was phytotoxic. Si treatments applied at 100 mM pre-inoculation with T. roseum had lower decay incidence and severity than treatments applied post-inoculation. The protection of Si was correlated with the activation of two families of defense-related enzymes, peroxidase and chitinase. Accumulation of both enzymes was induced in fruit treated with Si and challenged by T. roseum 24 h later, and was sustained for at least 9 days in ‘New Queen’ and 10 days in ‘8601’ at room temperature. It appeared that induced resistance was an important mechanism of disease control in Hami melons treated with Si.

The role of silicon (Si) in increasing plant resistance against fungal diseases

“…Regarding Cryptococcus laurentii-sweet cherry interaction, increased polyphenol oxidase activity reduced disease severity in fruit treated with 1% silicon (Qin and Tian, 2005). Enhanced peroxidase activity in melon plants treated with sodium silicate decreased incidence of pink rot caused by Trichothecium roseum (Bi et al, 2006). Increased rice resistance due to silicon treatment against the brown spot pathogen (Bipolaris oryzae) seems to be the result of higher levels of chitinase and peroxidase (Dallagnol et al, 2011).…”

“…Also, the potassium silicate concentrations used by Bekker et al (2006) were 50 to 60 times higher than those in Shen's et al (2010) study. Moreoever, these concentrations (Bekker et al, 2006;Bi et al, 2006) are unrealistic for fi eld use because the high pH of the resulting potassium silicate solutions could cause phytotoxicity. Shen et al (2010) concluded that the reduction in fungal diseases following treatment of fi eld plants with silicon is probably not due to the fungistatic eff ects of silicon, but to other biochemical and physical mechanisms mentioned previously.…”

Stimulateurs des défenses naturelles des plantes : une nouvelle stratégie phytosanitaire dans un contexte d’écoproduction durable.

“…Ce produit est présenté comme étant un biopesticide à triple activité : fongicide, insecticide et arachnicide. Le concept d'une induction de résistance par la silice a largement été confirmé au cours des dernières années, qu'il s'agisse du melon (Cucumis melo L.) (Bi et al 2006), de la cerise (Prunus avium L.) (Qin et Tian 2005) ou de la fraise (Kanto et al 2007). …”

Cloning and expression of class I chitinases in Hami melon after Penicillium infection

“…Some treatments have been found to improve disease resistance in Hami melon. For example, the application of natamycin in combination with bilayer films consisting of chitosan and polyethylene wax have been shown to inhibit the growth of Alternaria alternate and Fusarium semitectum on the melon surface (Cong et al, 2007), while sodium silicate treatment has been found to inhibit the growth of Trichothecium roseum (Bi et al, 2006).…”