豆蔻酸和棕榈酸诱导茄子根际拮抗菌与黄萎菌数量消长的关系

以气质联用仪(GC-MS)鉴定的嫁接茄与自根茄根系分泌物主要差异成分豆蔻酸和棕榈酸,利用它们的模拟物质研究了其对茄子根际土壤黄萎菌拮抗真菌与细菌数量和根际土壤黄萎菌数量的影响,明确了两模拟成分对茄子根际拮抗真菌和拮抗细菌的诱导作用及对黄萎菌数量抑制效果。同时,进一步分析了茄子根际拮抗真菌与细菌数总和与根际土壤黄萎菌数量的相关性。结果表明豆蔻酸和棕榈酸处理,茄子根际拮抗真菌和细菌数量均有所增加,在中高浓度下拮抗真菌和细菌数量增加显著。两物质处理下拮抗真菌与细菌数量在开花期和结果期增加显著。两物质对茄子根际黄萎菌数量的影响,整体来说,随两模拟组分浓度的增加土壤黄萎菌数量有所减少,各时期表现有所差异,在开花期两物质处理显著减少了黄萎菌数量。相关性分析表明豆蔻酸和棕榈酸处理下茄子根际拮抗真菌与细菌总量与根际黄萎菌数量呈显著的负相关性。说明嫁接通过改变茄子根系分泌物成分与对茄子根际土壤黄萎菌拮抗菌的诱导有一定关系。

Population fluctuations of antagonistic microbes and Verticillium dahliae influenced by myristic and palmitic acids in root exudates present in eggplant rhizospheres

Microorganisms with antagonist effects against the fungus Verticillium dahliae exist in the rhizospheres of grafted eggplants. Gas chromatography mass spectrometry (GC-MS) identifies both myristic acid and palmitic acid in the root exudates of grafted eggplants, which are absent in self-rooted controls; however, it is unknown whether these compounds affect microbes that are antagonistic towards V. dahliae. This study examined the allelopathic effects of myristic and palmitic acids on beneficial microbes and pathogens. We investigated the numbers of antagonistic fungi and bacteria and the numbers of microsclerotia of V. dahliae in rhizospheres of eggplants treated with myristic or palmitic acid. In addition, we examined the relationship between the antagonistic microbes and the V. dahliae in rhizospheres. Both myristic acid and palmitic acid were found to significantly increase colony-forming units (CFUs) of antagonistic fungi and bacteria, in a dose-dependent manner. However, these effects varied with stage. At lower concentrations of myristic acid, antagonistic microbes varied significantly at florescence. The effect of palmitic acid treatment was greatest at the fruiting stage. Moreover, increased concentrations of either compound correlated with a reduction of V. dahliae in the rhizosphere; again, the effects varied with stage. For example, the anti-fungal effect of myristic acid was most marked at florescence. In contrast, a low concentration of palmitic acid led to an increase in V. dahliae at florescence, but this effect was reversed at high concentrations. Moreover, a negative correlation was found between numbers of antagonistic microbes and V. dahliae in the rhizosphere. In the myristic acid treatment, the correlation coefficient was -0.8215 at the flower budding stage. Both the correlation coefficient and the determinative coefficient decreased concomitantly with eggplant growth stage. In the palmitic acid treatment, both coefficients displayed a parabolic trend:antagonistic microbe numbers increased concomitantly with a decrease in V. dahliae. The largest negative correlation occurred at florescence. This phenomenon may be due to stronger competitive effects of beneficial microorganisms. They first occupy colonization loci on the root to pathogenic bacteria nonviable in the rhizosphere. Therefore, it is likely that grafting alters the makeup of eggplant root exudates, which influence rhizosphere microbes and, in turn, affect the development of V. dahliae.