Dean Der-Syh Tzeng’s research while affiliated with National Chung Hsing University and other places

A multitude of potential pathogens are present in the plant environment. Yet disease is the exception not the rule. Thus, plant defence responses are generally sound (Huang, 1998). The major defence responses in higher plants against bacterial, fungal, viral, and nematode infection are elicitation of the hypersensitive reaction (HR) (Goodman and Novacky, 1994), accumulation of phytoalexins (Pierce et al., 1996), fortification of cell walls with lignin and hydroxyproline-rich glycoproteins (Moerschbacher et al., 1990; Bestwick et al., 1995) and biosynthesis of pathogenesis-related (PR) proteins (Stintzi et al., 1993).

Foliar application of a mixture of methionine (1 mM) and riboflavin (26.6 μM) reduced the severity of powdery mildew [Sphaerotheca macularia (Wallr. ex Fr.) Jacz. f. sp. fragariae] infection in 'Earligiow' strawberry (Fragaria x ananassa Duch.) plants. Efficacy of this mixture on controlling powdery mildew infection was enhanced by supplements of copper, iron, and surfactants [sodium dodecyl sulfate (SDS), Triton X-100, Tween-20, or oxyalkylenemethylsiloxane (Silwet L-77)]. Free-radical scavengers (n-propyl gallate, thiourea) and antioxidants (α-tocopherol, β-carotene) reduced the efficacy of this mixture. Plants treated with a mixture of riboflavin (26.6 μM), D,L-methionine (1 mM), copper sulfate pentahydrate (1 mM), and surfactants (SDS or Silwet L-77 at concentrations of 0.05% to 0.1%) showed a decrease in powdery mildew infection. Results of this study suggest that treatment with a mixture of methionine and riboflavin is beneficial to strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.

Foliar application of a mixture of methionine and riboflavin was effective in reducing the severity of powdery mildew [ Sphaerotheca macularia (Wallr. ex Fr.) Jacz. F. sp. Fragariae] infection in 72 strawberry progenies and over 110 clonal genotypes. This biocidal activity was enhanced by supplement of copper, iron, and surfactants [such as sodium dodecyl sulfate (SDS), Triton X-100, or Tween-20]. Compounds free radical scavengers (n-propyl gallate, thiourea), or antioxidants (α-tocopherol, -carotene) reduced its biocidal activity. Plants treated with the MR formulation (26.6 μM riboflavin, 1 mM D,L-methionine, 1 mM copper sulfate pentahydrate and 1 mg·ml–1 SDS) or 29% SP formulation of MR (Technical Division of the American Cyanamid Corporation, Taiwan Subsidiary at Taipei) not only showed decreased powdery mildew infection but also showed increased chlorophyll content and leaf area and improved fruit quality. Results in this study suggest that treatment with mixture of methionine and riboflavin is beneficial to strawberry plants and may serve as an alternative to fungicides for controlling powdery mildew.