Universidade Federal de Minas Gerais - UFMG, Departamento de Microbiologia, Belo Horizonte, MG, Brasil.
Embrapa Milho e Sorgo - CNPMS, Laboratório de Bioquímica Molecular, Sete Lagoas, MG, Brasil.
Braz J Biol. 2022 Aug 29;82:e262567. doi: 10.1590/1519-6984.262567. eCollection 2022.
The mycotoxigenic fungus Fusarium verticillioides is the primary maize pathogen and causes the maize stalk and ear rot diseases with significant economic losses. Furthermore, the excessive use of fungicides to control F. verticillioides constitutes threats to the environment and human health. Thus, sustainable alternatives such as biological control are needed to minimize the hazards associated with the current method. Although much is known about the vulnerability of the maize silks as a gateway for several fungal pathogens invading the developing grains, studies on the chemical properties of silk extracts and their resident microbiota are scarce. This study isolated and characterized bacteria and fungi that colonize the maize stigma to assess new potential biocontrol agents. The samples were collected from maize fields in the Brazilian localities of Sete Lagoas-MG, Sidrolândia-MS, Sertaneja-PR, and Goiânia-GO. One hundred sixty-seven microorganisms were isolated, 46% endophytic and 54% epiphytic. First, the antagonist activity was evaluated by the agar disc diffusion method performed in triplicate, and 83% of the isolates showed antagonist activity against F. verticillioides. Then, the 42 most efficient isolates were identified based on the partial sequencing of the bacterial 16S rRNA gene and fungi ITS region. The bacteria belong to the genera Bacillus (57.1%), Burkholderia (23.8%), Achromobacter (7.1%), Pseudomonas (2.4%), and Serratia (2.4%), while the fungi are Penicillium (2.4%), Candida (2.4), and Aspergillus (2.4%). The results showed that microorganisms from maize stigma might represent new promising agents for F. verticillioides control.
产毒素真菌轮枝镰孢菌是主要的玉米病原体，可引起玉米茎和穗腐病，造成重大经济损失。此外，为了控制轮枝镰孢菌而过度使用杀菌剂对环境和人类健康构成威胁。因此，需要可持续的替代方法，如生物防治，以最大限度地减少当前方法带来的危害。虽然人们已经了解到，玉米花丝作为几种真菌病原体侵入发育中的谷物的门户，非常脆弱，但关于丝提取物的化学性质及其驻留菌群的研究却很少。本研究分离并鉴定了定殖于玉米柱头的细菌和真菌，以评估新的潜在生物防治剂。这些样本是从巴西塞特兰迪亚、米纳斯吉拉斯州锡多罗内尼亚、巴西南里奥格兰德州塞塔内贾和戈亚尼亚等地的玉米地采集的。共分离出 167 种微生物，其中 46%为内生菌，54%为外生菌。首先，通过重复进行琼脂圆盘扩散法评估了拮抗菌的拮抗活性，结果显示 83%的分离物对轮枝镰孢菌具有拮抗活性。然后，根据细菌 16S rRNA 基因和真菌 ITS 区的部分测序结果，对 42 种最有效的分离物进行了鉴定。这些细菌属于芽孢杆菌属（57.1%）、伯克霍尔德菌属（23.8%）、不动杆菌属（7.1%）、假单胞菌属（2.4%）和沙雷氏菌属（2.4%），而真菌属于青霉属（2.4%）、假丝酵母属（2.4%）和曲霉属（2.4%）。结果表明，玉米柱头的微生物可能代表控制轮枝镰孢菌的新的有前途的制剂。
