Residual polysaccharides from fungi reduce the bacterial spot in tomato plants

Abstract Polysaccharides from fungal wastes were partially characterized and evaluated for their protective effects against bacterial spot caused by Xanthomonas gardneri on four tomato cultivars: Santa Cruz Kada, Natália, BRS Sena and Forty. The polysaccharides were extracted from spent mushroom substrate of Pleurotus ostreatus, residual brewery yeast (Saccharomyces cerevisiae), and basidiocarps discarded from Lentinula edodes production. These polysaccharides were characterized for total carbohydrates, phenolics and proteins content, pH, scatter intensity, conductivity, Zeta potential, DPPH scavenging assay and infrared spectroscopy. The effects of time interval between treatment and inoculation (4 or 7 days) and polysaccharide concentrations (0.5 or 1.5 mg.mL–1) were assessed for disease severity using a susceptible tomato cultivar. The polysaccharide action mode was investigated by determining the activity of peroxidases and phenylalanine ammonialyase and by quantifying flavonoids and total phenolics in the plants treated and challenged with X. gardneri. The polysaccharides obtained from Lentinula edodes (PSHII), Saccharomyces cerevisiae (PRC) and Pleurotus ostreatus (PSPO) (1.5 mg.mL-1) reduced bacterial spot severity by 50% on tomato cotyledons, leaflets and five-leaf plants. Furthermore, PRC and PSHII (1.5 mg.mL–1) could decrease disease severity in all tested cultivars. PSHII, the most effective, did not cause change in phenylalanine ammonia-lyase activity or flavonoid content on the cultivars Kada and Natália. However, an increase in peroxidase activity and total phenol content on cv. Kada was noted. The polysaccharides obtained from food industry wastes could provide protection against bacterial spot on tomato cultivars by inducing defense mechanisms and can be useful in formulating products with phytosanitary potential.

摘要：本研究对真菌源废弃物多糖开展初步表征，并评估其对Santa Cruz Kada、Natália、BRS Sena、Forty四个番茄品种上由野油菜黄单胞菌（Xanthomonas gardneri）引起的细菌性斑点病的防控效果。多糖提取自平菇（Pleurotus ostreatus）菌渣、酿酒酵母（Saccharomyces cerevisiae）酿造副产物酵母残体及香菇（Lentinula edodes）生产废弃子实体。本研究对所得多糖开展多维度表征分析，包括总碳水化合物、酚类与蛋白质含量、pH值、散射强度、电导率、Zeta电位、DPPH自由基清除试验及红外光谱分析。本研究选用易感番茄品种，评估了施药与病原菌接种间隔时长（4天或7天）及多糖施用浓度（0.5或1.5 mg·mL⁻¹）对病害严重度的影响。通过测定过氧化物酶（peroxidases）与苯丙氨酸解氨酶（phenylalanine ammonialyase）的活性，以及定量分析接种野油菜黄单胞菌（X. gardneri）的处理植株体内黄酮类与总酚类物质含量，解析了该类多糖的作用机制。结果显示，浓度为1.5 mg·mL⁻¹时，从香菇（Lentinula edodes）提取的多糖（PSHII）、酿酒酵母（Saccharomyces cerevisiae）提取的多糖（PRC）和平菇（Pleurotus ostreatus）提取的多糖（PSPO）可使番茄子叶、小叶及五叶期植株的细菌性斑点病严重度降低50%。此外，浓度为1.5 mg·mL⁻¹的PRC与PSHII可降低所有供试番茄品种的病害严重度。其中防控效果最优的PSHII，在Kada与Natália品种上不会改变苯丙氨酸解氨酶活性及黄酮类物质含量，但可提升Kada品种的过氧化物酶活性与总酚类物质含量。本研究表明，源自食品工业废弃物的多糖可通过诱导植物防御机制，为番茄品种提供细菌性斑点病防控保护，具备开发为具有植保潜力产品的应用价值。