Department of Agricultural Microbiology, Faculty of Agricultural Sciences, Aligarh Muslim University, Aligarh, 202002, Uttar Pradesh, India.
Department of Botany and Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh, 11451, Saudi Arabia.
Sci Rep. 2021 May 6;11(1):9655. doi: 10.1038/s41598-021-89103-9.
Fungicides among agrochemicals are consistently used in high throughput agricultural practices to protect plants from damaging impact of phytopathogens and hence to optimize crop production. However, the negative impact of fungicides on composition and functions of soil microbiota, plants and via food chain, on human health is a matter of grave concern. Considering such agrochemical threats, the present study was undertaken to know that how fungicide-tolerant symbiotic bacterium, Mesorhizobium ciceri affects the Cicer arietinum crop while growing in kitazin (KITZ) stressed soils under greenhouse conditions. Both in vitro and soil systems, KITZ imparted deleterious impacts on C. arietinum as a function of dose. The three-time more of normal rate of KITZ dose detrimentally but maximally reduced the germination efficiency, vigor index, dry matter production, symbiotic features, leaf pigments and seed attributes of C. arietinum. KITZ-induced morphological alterations in root tips, oxidative damage and cell death in root cells of C. arietinum were visible under scanning electron microscope (SEM). M. ciceri tolerated up to 2400 µg mL of KITZ, synthesized considerable amounts of bioactive molecules including indole-3-acetic-acid (IAA), 1-aminocyclopropane 1-carboxylate (ACC) deaminase, siderophores, exopolysaccharides (EPS), hydrogen cyanide, ammonia, and solubilised inorganic phosphate even in fungicide-stressed media. Following application to soil, M. ciceri improved performance of C. arietinum and enhanced dry biomass production, yield, symbiosis and leaf pigments even in a fungicide-polluted environment. At 96 µg KITZ kg soil, M. ciceri maximally and significantly (p ≤ 0.05) augmented the length of plants by 41%, total dry matter by 18%, carotenoid content by 9%, LHb content by 21%, root N by 9%, shoot P by 11% and pod yield by 15% over control plants. Additionally, the nodule bacterium M. ciceri efficiently colonized the plant rhizosphere/rhizoplane and considerably decreased the levels of stressor molecules (proline and malondialdehyde) and antioxidant defence enzymes viz. ascorbate peroxidise (APX), guaiacol peroxidise (GPX), catalase (CAT) and peroxidises (POD) of C. arietinum plants when inoculated in soil. The symbiotic strain effectively colonized the plant rhizosphere/rhizoplane. Conclusively, the ability to endure higher fungicide concentrations, capacity to secrete plant growth modulators even under fungicide pressure, and inherent features to lower the level of proline and plant defence enzymes makes this M. ciceri as a superb choice for augmenting the safe production of C. arietinum even under fungicide-contaminated soils.
杀菌剂作为农用化学品，在高通量农业实践中被广泛用于保护植物免受植物病原菌的破坏性影响，从而优化作物产量。然而，杀菌剂对土壤微生物群落、植物以及食物链组成和功能的负面影响，对人类健康构成了严重关切。考虑到这种农用化学品的威胁，本研究旨在了解具有抗真菌特性的共生细菌，根瘤菌（Mesorhizobium ciceri）在温室条件下生长于 Kitazin（KITZ）胁迫土壤中时，如何影响鹰嘴豆（Cicer arietinum）作物。在体外和土壤系统中，KITZ 以剂量依赖的方式对 C. arietinum 产生有害影响。KITZ 剂量正常水平的三倍多会严重但最大程度地降低鹰嘴豆的发芽效率、活力指数、干物质产量、共生特征、叶片色素和种子特性。扫描电子显微镜（SEM）下可见 KITZ 诱导的鹰嘴豆根尖形态改变、根细胞的氧化损伤和细胞死亡。M. ciceri 可耐受高达 2400µg/mL 的 KITZ，合成了大量生物活性分子，包括吲哚-3-乙酸（IAA）、1-氨基环丙烷 1-羧酸（ACC）脱氨酶、铁载体、胞外多糖（EPS）、氢氰酸、氨和可溶无机磷酸盐，即使在杀菌剂胁迫的培养基中也是如此。在土壤中应用后，M. ciceri 提高了鹰嘴豆的性能，并在杀菌剂污染的环境中提高了干生物量产量、产量、共生和叶片色素。在 96µg KITZ kg 土壤中，M. ciceri 最大程度地显著（p≤0.05）增加了植物的长度 41%，总干物质 18%，类胡萝卜素含量 9%，LHb 含量 21%，根氮 9%，茎叶磷 11%，荚果产量 15%，对照植物。此外，接种于土壤中的根瘤菌 M. ciceri 能够有效地定殖植物根际/根面，并显著降低胁迫分子（脯氨酸和丙二醛）和抗氧化防御酶（抗坏血酸过氧化物酶（APX）、愈创木酚过氧化物酶（GPX）、过氧化氢酶（CAT）和过氧化物酶（POD））的水平。共生菌株有效地定殖了植物根际/根面。总之，该菌株能够耐受更高浓度的杀菌剂，即使在杀菌剂压力下也能分泌植物生长调节剂，并且固有特性可降低脯氨酸和植物防御酶的水平，这使得 M. ciceri 成为在杀菌剂污染土壤中提高鹰嘴豆安全产量的绝佳选择。
