西瓜、水稻根分泌物及酚酸类物质对西瓜专化型尖孢镰刀菌的影响#br#

 【目的】探讨西瓜、水稻根分泌物及其中的酚酸类物质对西瓜专化型尖孢镰刀菌(Fusarium oxysporum f. sp. niveum,FON)的影响,阐释西瓜枯萎病的发生和西瓜/旱作水稻间作系统改善西瓜连作枯萎病的机理。【方法】营养液培养法收集西瓜根分泌物(REW)和水稻根分泌物(RER),研究其对FON生长的影响;HPLC法分离鉴定REW和RER中的酚酸类物质,并通过外源添加法研究该类物质对FON生长的影响。【结果】REW能显著促进FON孢子萌发和产孢,与对照相比,1.0 mL和5.0 mL 的REW对FON孢子萌发的促进率分别为46.9%和59.2%;在0.1 mL至2.0 mL范围内,REW对FON产孢的促进率从10.8 %逐渐增加到84.6 %;而RER能显著抑制FON孢子萌发和产孢,1.0 mL和5.0 mL RER对FON孢子萌发抑制率分别为14.3 %和6.1 %;并在0.1 mL至2.0 mL范围内,对该菌产孢的抑制率由4.6%增至37.5%。在REW和RER中同时检测到水杨酸、对羟基苯甲酸和邻苯二甲酸,而阿魏酸和香豆酸分别单独存在于REW和RER中;且RER中以香豆酸含量最高(占总量的37.9%);其酚酸总量是REW的1.4倍。综合FON孢子萌发、产孢能力和菌丝生长三项测定指标,香豆酸的抑菌效果最显著,抑制率分别为9.1%—70.5%、24.1%—100.0%和2.5%—47.5%,其次是水杨酸;而阿魏酸、对羟基苯甲酸、邻苯二甲酸对FON孢子萌发、产孢有不同程度的促进作用,以阿魏酸最为突出,浓度为40—160 mg•L-1时促进率分别为28.6%—114.3%和17.7%—54.8%。【结论】西瓜根分泌物对FON有刺激作用而水稻根分泌物对FON却具有抑制作用,这为阐释西瓜/旱作水稻间作系统改善西瓜连作枯萎病提供了理论依据。

Effects of Root Exudates from Watermelon, Rice Plants and Phenolic Acids on Fusarium oxysporum f. sp. niveum

【Objective】 The objectives of this study were to compare influence of allelochemicals from root exudates of watermelon and rice plants on the growth of FON and to clarify the mechanism of disease suppressiveness in the intercropping system. 【Method】 Root exudates of watermelon (REW) and rice (RER) plants were collected by nutrient solution culture. The effects of REW and RER on FON were determined by culture medium method. The phenolic acids of REW and RER were identified by HPLC. Exogenous phenolic acids were also used to investigate the effect of some phenolic acids, which existed in REW and RER, on FON. 【Result】Compared with the control, addition of 1.0 mL and 5.0 mL of REW increased the numbers of germinating spores by 46.9% and 59.2%, respectively, while the spore reproduction was enhanced by 10.8% to 84.6% when REW was added in the range from 0.1 to 2.0 mL. In contrast, addition of 1.0 mL and 5.0 mL of RER decreased spore germination by 14.3% and 6.1%, respectively, while addition of REW from 0.1 mL to 2.0 mL decreased spore reproduction by 4.6% to 37.5%. Salicylic acid, p-hydroxybenzoic acid and phthalic acid were identified in both RER and REW by HPLC analysis, but ferulic and p-coumaric acid acid were detected exclusively in REW and RER, respectively. Moreover, the content of p-coumaric acid was the highest among phenolic acids in RER, accounting for 37.9% of the total amount of phenolic acids, which was 1.4-fold as high as that in REW. According to the effects of exogenous phenolic acids on spore germination, spore reproduction and mycelial growth of FON, p-coumaric acid had the most significant inhibitory effects, followed by salicylic acid. In detail, exogenous p-coumaric reduced spore germination by 9.1% to 70.5%, spore reproduction by 24.1% to 100.0% and mycelial growth by 2.5% to 47.5%, as compared with the controls. In contrast, ferulic acid, p-hydroxybenzoic acid and phthalic acid increased spore germination and spore reproduction to some extent. Among of them, ferulic acid had the obvious promoting effects and could enhance spore germination by 28.6% to 114.3% and spore reproduction by 17.7% to 54.8% when its concentration ranging from 40 to 160 mg•L-1. 【Concluion】 It was concluded that the root exudates from rice plants were fungistatic while those from watermelon were pathogen-promotive. This finding provided a scientific basis for clarifying the mechanism of disease suppressiveness of watermelon in the watermelon/aerobic rice intercropping system.