苯甲酸胁迫下间作对蚕豆自毒效应的缓解机制

苯甲酸是引起蚕豆连作障碍的主要自毒物质之一。本文采用水培试验,研究了不同浓度苯甲酸C0(0 mg?L-1)、C1(50 mg?L-1)、C2(100 mg?L-1)和C3(200 mg?L-1)]处理对与小麦间作的蚕豆幼苗生长和枯萎病发生的影响,从生理抗性角度探讨小麦与蚕豆间作对缓解苯甲酸自毒效应的机制,为合理利用间作缓解连作障碍,实现农业可持续发展提供科学依据。结果表明:与C0处理相比,不同浓度苯甲酸处理均显著抑制了蚕豆幼苗的生长,并且随处理浓度升高,抑制效应增强;同时显著提高了蚕豆枯萎病发病率和病情指数;蚕豆根系和叶片的MDA含量显著提高,但抗氧化酶(POD和CAT)活性和病程相关蛋白(β-1,3-葡聚糖酶和几丁质酶)活性均随苯甲酸处理浓度升高而降低。表明不同浓度苯甲酸处理均显著抑制了蚕豆的生长,降低蚕豆的生理抗性而促进枯萎病发生。与单作蚕豆相比,蚕豆与小麦间作显著提高了苯甲酸胁迫下蚕豆的地上部干重(17.0%~47.1%),降低了发病率(11.1%~25.0%)和病情指数(20.0%~42.1%);蚕豆根系和叶片中POD活性分别提高12.9%~16.9%和9.3%~24.9%,CAT活性分别提高10.3%~54.0%和6.6%~20.5%,蚕豆根系的β-1,3-葡聚糖酶和几丁质酶活性分别提高4.7%~13.1%和6.7%~15.8%,MDA含量分别降低19.5%~25.4%和20.5%~29.9%。C2处理下间作提高抗氧化酶和病程相关蛋白活性的效果最好,抗病效果最佳。表明小麦与蚕豆间作通过提高蚕豆的生理抗性而减轻苯甲酸引起的枯萎病危害,促进蚕豆生长,是缓解苯甲酸自毒效应的有效措施。

Alleviation mechanism of intercropping with wheat for faba bean autotoxicity under benzoic acid stress

Continuous cropping of faba bean causes serious growth obstacle, and benzoic acid is one of the main autotoxins in faba bean continuous cropping. Faba bean-wheat intercropping is a general planting pattern in Southwest China. To investigate the effect of benzoic acid on faba bean seedling growth and Fusarium wilt occurrence, and to explore the effect and alleviation mechanism of intercropping with wheat on faba bean autotoxicity, a hydroponic experiment of faba bean-wheat intercropping with benzoic acid application was conducted in the greenhouse of Yunnan Agricultural University. Four benzoic acid rates were set, which were C0 (0 mg×L-1), C1 (50 mg×L-1), C2 (100 mg×L-1) and C3 (200 mg×L-1), with two planting patterns, faba bean monocropping and faba bean and wheat intercropping. The growth, enzymes activities and occurrence of faba bean Fusarium wilt were investigated. The results showed that in comparison with C0 treatment, seedling growth was inhibited with increasing benzoic acid concentration. Benzoic acid increased the incidence and disease index of monocropped faba bean Fusarium wilt, significantly increased root and leaf MDA contents, and decreased the activities of antioxidant enzyme (POD and CAT) and pathogenesis-related proteins (β-1, 3-glacanase and chitinase) with increasing application rates. Comparison with monocropped faba bean, intercropped faba bean increased shoot dry weight by 17.0%-47.1%, reduced disease incidence and disease index by 11.1%-25.0% and 20.0%-42.1%, respectively, under benzoic acid application. Furthermore, the peroxidase (POD) activity increased by 12.9%-16.9% in root and by 9.3%-24.9% in leaf; and the catalase (CAT) activity increased by 10.3%-54.0%in root and by 6.6%-20.5%in leaf under intercropped condition. Compared with monocropping of faba bean, intercropping with wheat increased faba bean β-1,3-glacanase and chitinase activities in root by 4.7%-13.1% and 6.7%-15.8%, while decreased malondialdehyde (MDA) contents in both root and leaf significantly by 19.5%-25.4% and 20.5%-29.9%, respectively, with benzoic acid application. Under C2 (100 mg×L-1) treatment of benzoic acid stress, faba bean-wheat intercropping system showed the best effect of improving pathogenesis-related proteins and antioxidative enzymes activity. Intercropping of faba bean-wheat significantly increased physiological resistance to Fusarium oxysporum f. fabae and significantly decreased the incidence of Fusarium wilt. Therefore, it alleviated the damage of Fusarium wilt caused by benzoic acid, and promoted growth of faba bean. Thus, intercropping with wheat was an effective method to alleviate faba bean autotoxicity caused by benzoic acid. The results also provided an experimental evidence for developing an ecological-economic and effective approach to control soil-borne diseases caused by continuous crop cultivation.