Fig. 1: Effect of d-tagatose on severity of various downy mildews.

Typical symptoms of cucumber downy mildew on the first true leaf of untreated cucumber plant and reduced severity after treatment with 1% or 5% (w/v) d-tagatose, d-allulose, or d-allose in pot trials in comparison with probenazole [PBZ], acibenzolar-S-methyl [ASM], and metalaxyl (Scale Bar = 5 cm) (a). The timing of treatments with sugars and agrochemicals in pot trials varied from 1 to 7 days before inoculation with the pathogen (“Preventive”) or from 12 to 72 h after inoculation (“Curative”), and their symptoms were compared using the averages of each severity after 7 days to calculate a relative disease severity against average severity for the mock-treated plants. Data presented are representative of three independent experiments (b). Severity of downy mildews in field trials after treatment with d-tagatose (1% or 5%, w/v) (d-Tag) compared (n = 50 to 163 leaves per group) with a fungicide: cyazofamid FL (CZF) at 94 parts per million (ppm) on grapevine and spinach downy mildews (c, g), chlorothalonil (CTN) FL at 400 ppm for cucumber and Chinese cabbage downy mildews (d, e), and mancozeb (MCZ) WP at 1875 ppm for onion downy mildew (f), or mock treatment (Untreated) (c–g). Disease severity was calculated from the degree of disease index based on the Fungicide Evaluation Manual by the Japan Plant Protection Association for field trials⁵¹ as described in the Methods. Data presented are representative of 3–4 independent experiments. Error bars are SD. Means with different letters differed significantly at p < 0.05 in a Tukey–Kramer multiple comparison test.