氟磺胺草醚对不同豆科作物生长及根际固氮菌的影响

为了研究豆田常用长残效除草剂氟磺胺草醚对不同季节豆科作物生长及根际固氮微生物的影响规律与机制,选取春大豆、四季豆、夏大豆、绿豆、蚕豆及豌豆为材料,于春、夏、秋季开展田间小区试验。通过对豆科作物地上部与根部性状的分析,明确不同浓度氟磺胺草醚对豆科作物的药害规律,采用荧光定量PCR技术分析固氮酶nifH基因丰度的变化,明确氟磺胺草醚对豆科作物根际固氮细菌的影响,并通过方差与相关性分析揭示不同豆科植物对氟磺胺草醚的响应模式差异。结果显示:氟磺胺草醚对夏大豆生长及产量无显著影响;1倍浓度(225 g·hm~(-2))氟磺胺草醚对春大豆、绿豆与豌豆不产生药害作用,且能够使绿豆与豌豆增产3.5%～17.5%,但2倍浓度(450 g·hm~(-2))会使这3种作物显著减产12.2%～19.6%;氟磺胺草醚对四季豆和蚕豆的药害作用严重,使作物产量显著下降23.0%～61.5%。豆科作物的产量与其根部性状显著相关,高浓度氟磺胺草醚会使6种豆科作物根鲜质量、根瘤数量、根瘤鲜质量均呈显著降低趋势。氟磺胺草醚的施用使作物根际固氮细菌的丰度显著下降,其变化趋势与豆科作物根部性状一致。研究建议氟磺胺草醚的施用量(有效成分用量)为:春大豆、绿豆、豌豆控制在225 g·hm~(-2),夏大豆可放宽至450 g·hm~(-2),四季豆和蚕豆不适宜施用氟磺胺草醚。研究表明,作物根际固氮细菌丰度的变化可能是导致结瘤能力改变的原因。

Effects of fomesafen on plant growth and nitrogen-fixing bacteria in the rhizosphere of different species of legumes

Fomesafen is a long-lasting herbicide commonly used in legume fields. To investigate effects of fomesafen on the growth of legume crops and the nitrogen-fixing bacteria in the plant rhizosphere in different seasons, field experiments were carried out in spring, summer, and autumn. The legumes of spring soybean, kidney bean, summer soybean, mung bean, broad bean, and pea were selected. The characteristics of the roots and shoots of the legumes were analyzed. The patterns of phytotoxicity of different dosages of fomesafen were determined. The effects of fomesafen on root nitrogen-fixing bacteria were analyzed via fluorescent quantitative polymerase chain reaction (PCR)of the nitrogenase gene nifH. The response patterns of the six species of legumes to fomesafen were revealed through variance and correlation analysis. Fomesafen had no significant effect on the growth and yield of summer soybeans. The low concentration of fomesafen (225 g·hm^-2)did not harm spring soybeans, green beans and peas, while increasing the yields of mung beans and peas by 3.5% to 17.5%. However, the high concentration of fomesafen(450 g·hm^-2) significantly reduced the yield of the three crops by 12.2% to 19.6%. Fomesafen was seriously harmful to kidney beans and broad beans, reducing their yield by 23.0% to 61.5%. The recommended application of fomesafen in spring soybean, green bean, and pea fields was 225 g·hm^-2. However, the application of fomesafen in summer soybeans field could be raised to 450 g·hm^-2. Furthermore, fomesafen was not feasible for kidney beans and broad beans. The yields of legume crops were positively correlated to their root characteristics. At a high concentration, fomesafen significantly reduced the root weights, quantities, and fresh weights exhibited by the nodules of the six species of legume crops. Fomesafen significantly reduced the abundances of the nifH gene in the rhizosphere of the legume crops. The variations in the abundance of crop root nitrogen-fixing bacteria may be responsible for the changes in nodulation.