ACCUMULATION OF PHYTOALEXINS IN BEANS, SOYBEANS AND SORGHUM BY FUNGAL FILTRATES

ABSTRACT The use of elicitors in plants for disease control is demonstrated by the accumulation of phytoalexins. Among these elicitors, metabolic products from fungi have been shown to be effective in the activation of mechanisms of induced resistance. Thus, this study aimed to evaluate the effects of filtrates from the saprobic fungi Curvularia inaequalis, Pseudobotrytis terrestris, Memnoniella echinata and Curvularia eragrostidis in inducing phaseolin, glyceolin and deoxyanthocyanidins. For this, fungal mycelial disks were liquid-subcultured in potato dextrose (BD) media and maintained in BOD at 25 °C and 12 h of light and darkness. After 20 days, the cultures were filtered and, the filtrates were used in the experiments. Phaseolin was measured in etiolated hypocotyls of bean. For glyceolin evaluation, cotyledons of soybean were used. The deoxyanthocyanidin accumulation was evaluated in etiolated mesocotyls of sorghum. The results were subjected to analysis of variance and compared by regression tests (p < 0.05). The filtrates of the saprobic fungi C. eragrostidis, C. inaequalis, P. terrestris and M. echinata promoted 9, 8, 9 and 7% greater increases in the concentration of phaseolin accumulations, respectively. The glyceolin accumulation varied with the concentration of C. eragrostidis, C. inaequalis and P. terrestris by adjusting the behavior to a cubic model. The deoxyanthocyanidin accumulation increased with concentration, while the filtrates of M. echinata and C. eragrostidis promoted 2 to 3 times more increases than the application of water. The filtrates of P. terrestris, C. eragrostidis, C. inaequalis and M. echinata induced accumulations of phytoalexins in soybean, beans and sorghum.摘要：利用植物激发子（elicitors）进行植物病害防控的效果，可通过植物抗毒素（phytoalexins）的积累得以验证。在各类激发子中，真菌代谢产物已被证实可有效激活植物诱导抗病性机制。据此，本研究旨在评估腐生真菌（saprobic fungi）不等弯孢霉（Curvularia inaequalis）、土生假葡萄孢（Pseudobotrytis terrestris）、棘状膜壳霉（Memnoniella echinata）及画眉草弯孢霉（Curvularia eragrostidis）的滤液，对菜豆素（phaseolin）、大豆素（glyceolin）与脱氧花青素（deoxyanthocyanidins）的诱导效果。为此，将真菌菌丝圆盘（mycelial disks）接种至马铃薯葡萄糖（BD）培养基中进行液体继代培养，随后置于25℃、光暗周期各12h的BOD恒温培养箱中培育。培养20天后对培养液进行过滤，所得滤液用于后续实验。菜豆素（phaseolin）的含量检测以菜豆黄化下胚轴（etiolated hypocotyls）为材料；大豆素（glyceolin）的评估采用大豆子叶作为实验样本；脱氧花青素（deoxyanthocyanidins）的积累量则通过高粱黄化中胚轴（etiolated mesocotyls）进行测定。实验数据采用方差分析（analysis of variance）进行处理，并通过回归检验（regression tests）进行多重比较，检验水准设为p<0.05。结果显示，画眉草弯孢霉、不等弯孢霉、土生假葡萄孢及棘状膜壳霉的滤液，可分别使菜豆素的积累浓度提升9%、8%、9%与7%。土生假葡萄孢、不等弯孢霉与画眉草弯孢霉的滤液对大豆素积累的影响符合三次回归模型。脱氧花青素的积累量随滤液浓度升高而增加，其中棘状膜壳霉与画眉草弯孢霉的滤液诱导提升效果为清水对照的2~3倍。综上，土生假葡萄孢、画眉草弯孢霉、不等弯孢霉及棘状膜壳霉的滤液，均可在大豆、菜豆与高粱中诱导植物抗毒素的积累。