Department of Soil Science, School of Agriculture, Shiraz University, Shiraz, Iran.
Soil and Water Research Institute, Agriculture Research, Education and Extension Organization, Karaj, Iran.
J Appl Microbiol. 2021 Aug;131(2):898-912. doi: 10.1111/jam.14975. Epub 2021 Jan 4.
The present study aimed at gaining an insight into the abundance and genetic diversity of culturable N-fixing epiphyte bacteria on the phyllosphere of maize in arid and semi-arid regions of Iran.
Leaf samples of the maize variety, 'single cross 704' (Zea mays L.) were collected from different locations in Iran. The community of culturable N-fixing epiphyte bacteria present was examined by 16S rRNA sequencing, BOXAIR-polymerase chain reaction (PCR) and restricted fragment length polymorphisms analysis of 16S rRNA gene (16S-RFLP). Approximately, 31·82% of the 242 isolates were identified as N-fixers by cultivation of bacteria in Rennie medium and detection of their nifH gene. The N-fixers were affiliated with four bacterial phyla: Firmicutes, Proteobacteria, Actinobacteria and Bacteroidetes. 16S rRNA sequencing detected 16 genera and 24 different species in the identified phyla. The most dominant genus was Bacillus and the species identified were B. pumilus, B. amyloliquefaciens, B. subtilis, B. paralicheniformis, B. licheniformis, B. niabensis and B. megaterium. In total, 22 RFLP groups were present among the isolates originally identified as N-fixing bacteria. BOXAIR-PCR showed that there was a low similarity level among the N-fixing bacteria isolates, and genetic differentiation of individual strains was relatively great.
Our findings suggest that nitrogen-fixing epiphyte bacteria on the phyllosphere of maize may provide significant nitrogen input into arid and semi-arid ecosystem.
This research implies that phyllosphere epiphyte diazotrophs have much to offer in sustainable agriculture and can be an alternative to chemical N-fertilizers for providing nitrogen to crops arid and semi-arid regions.
本研究旨在深入了解伊朗干旱和半干旱地区玉米叶片上可培养固氮附生菌的丰度和遗传多样性。
从伊朗不同地区采集玉米品种“单交 704”（Zea mays L.）的叶片样本。通过 16S rRNA 测序、BOXAIR-聚合酶链反应（PCR）和 16S rRNA 基因限制性片段长度多态性分析（16S-RFLP）检测存在的可培养固氮附生菌群落。通过在 Rennie 培养基中培养细菌并检测其 nifH 基因，约 31.82%的 242 个分离株被鉴定为固氮菌。固氮菌隶属于 4 个细菌门：厚壁菌门、变形菌门、放线菌门和拟杆菌门。在鉴定的门中，16S rRNA 测序检测到 16 个属和 24 个不同种。最主要的属是芽孢杆菌，鉴定出的种有短小芽孢杆菌、解淀粉芽孢杆菌、枯草芽孢杆菌、副地衣芽孢杆菌、地衣芽孢杆菌、尼亚布芽孢杆菌和巨大芽孢杆菌。在最初鉴定为固氮菌的分离株中，共存在 22 个 RFLP 群。BOXAIR-PCR 显示，固氮菌分离株之间的相似度水平较低，个别菌株的遗传分化较大。
我们的研究结果表明，玉米叶片上的固氮附生菌可能为干旱和半干旱生态系统提供大量氮素输入。
这项研究表明，叶际固氮附生菌在可持续农业中有很大的应用前景，可以作为化学氮肥的替代品，为干旱和半干旱地区的作物提供氮素。
