Hyder Sajjad, Gondal Amjad Shahzad, Rizvi Zarrin Fatima, Atiq Rashida, Haider Muhammad Irtaza Sajjad, Fatima Nida, Inam-Ul-Haq Muhammad
Department of Botany, Government College Women University, Sialkot, Pakistan.
Department of Plant Pathology, Bahauddin Zakariya University, Multan, Pakistan.
Front Microbiol. 2021 May 13;12:587431. doi: 10.3389/fmicb.2021.587431. eCollection 2021.
is a notorious soil-borne oomycete that causes post-emergence damping-off in chili pepper. Of various disease management strategies, utilization of plant growth promoting rhizobacteria (PGPR) in disease suppression and plant growth promotion is an interesting strategy. The present study was performed to isolate and characterize PGPR indigenous to the chili rhizosphere in Pakistan, and to test the potential to suppress the damping-off and plant growth promotion in chili. Out of a total of 28 antagonists, eight bacterial isolates (4a2, JHL-8, JHL-12, 1C2, RH-24, 1D, 5C, and RH-87) significantly suppressed the colony growth of in a dual culture experiment. All the tested bacterial isolates were characterized for biochemical attributes, and 16S rRNA sequence based phylogenetic analysis identified these isolates as spp., , , , and . All the tested bacterial isolates showed positive test results for ammonia production, starch hydrolase (except 4a2), and hydrogen cyanide production (except 4a2 and 1D). All the tested antagonists produced indole-3-acetic acid (13.4-39.0 μg mL), solubilized inorganic phosphate (75-103 μg mL), and produced siderophores (17.1-23.7%) . All the tested bacterial isolates showed varying levels of susceptibility and resistance response against different antibiotics and all these bacterial isolates were found to be non-pathogenic to chili seeds and notably enhanced percentage seed germination, plumule, redical length, and vigor index over un-inoculated control. Additionally, under pathogen pressure, bacterization increased the defense related enzymes such as Peroxidase (PO), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) activates. Moreover, the treatment of chili seeds with these bacterial isolates significantly suppressed the damping-off caused by and improved PGP traits compared to the control. In addition, a positive correlation was noticed between shoot, root length, and dry shoot and root weight, and there was a negative correlation between dry shoot, root weight, and seedling percentage mortality. These results showed that native PGPR possesses multiple traits beneficial to the chili plants and can be used to develop eco-friendly and effective seed treatment formulation as an alternative to synthetic chemical fungicides.
是一种臭名昭著的土传卵菌，可导致辣椒出苗后猝倒病。在各种病害管理策略中，利用植物促生根际细菌（PGPR）来抑制病害和促进植物生长是一种有趣的策略。本研究旨在分离和鉴定巴基斯坦辣椒根际的本土PGPR，并测试其抑制辣椒猝倒病和促进辣椒生长的潜力。在总共28种拮抗菌中，8株细菌分离物（4a2、JHL-8、JHL-12、1C2、RH-24、1D、5C和RH-87）在双培养实验中显著抑制了的菌落生长。对所有测试的细菌分离物进行了生化特性鉴定，基于16S rRNA序列的系统发育分析将这些分离物鉴定为 spp.、、、、和。所有测试的细菌分离物在氨产生、淀粉水解酶（4a2除外）和氰化氢产生（4a2和1D除外）方面均显示阳性测试结果。所有测试的拮抗菌均产生吲哚-3-乙酸（13.4 - 39.0 μg mL），溶解无机磷（75 - 103 μg mL），并产生铁载体（17.1 - 23.7%）。所有测试的细菌分离物对不同抗生素表现出不同程度的敏感性和抗性反应，并且发现所有这些细菌分离物对辣椒种子无致病性，与未接种对照相比，显著提高了种子发芽率、胚芽、胚根长度和活力指数。此外，在病原菌压力下，接种细菌增加了防御相关酶如过氧化物酶（PO）、多酚氧化酶（PPO）和苯丙氨酸解氨酶（PAL）的活性。此外，用这些细菌分离物处理辣椒种子显著抑制了引起的猝倒病，并与对照相比改善了植物促生特性。此外，在地上部、根长与地上部和根干重之间观察到正相关，而在地上部、根干重与幼苗死亡率百分比之间存在负相关。这些结果表明，本土PGPR具有对辣椒植株有益的多种特性，可用于开发生态友好且有效的种子处理配方，作为合成化学杀菌剂的替代品。
