Tarroum Mohamed, Ben Romdhane Walid, Ali Ahmed Abdelrahim Mohamed, Al-Qurainy Fahad, Al-Doss Abdullah, Fki Lotfi, Hassairi Afif
Laboratory of Plant Biotechnology Applied to Crop Improvement, Faculty of Sciences of Sfax, University of Sfax, B.P. 802, Sfax 3038, Tunisia.
Department of Botany and Microbiology, College of Science, King Saud University, Riyadh 11451, Saudi Arabia.
Plants (Basel). 2021 Apr 16;10(4):784. doi: 10.3390/plants10040784.
Hydroponic systems have gained interest and are increasingly used in hot and dry desert areas. Numbers of benefits are offered by hydroponic systems such as the ability to save water, enhance nutrients use efficiency, easy environmental control, and prevention of soil-borne diseases. However, the high consumption of chemical fertilizers for nutrient solution and the sensitivity of closed hydroponic systems to salinity are issues that need solutions. Thus, the main goal of our research activities is to isolate plant growth promoting fungi in order to develop sustainable hydroponic systems. We are working on isolating and testing the possibility to incorporate the cell-free filtrate (CFF) of plant growth promoting fungi (PGPF) in the composition of the nutrient solution. In this work, we isolated six strains of PGPF from the rhizosphere of the halophyte grass . Phylogenetic analyses of DNA sequences amplified by ITS1 and ITS4 primers identified the isolated fungi as: , , , , , and . The promoting of vigor in tobacco seedlings was used as criteria to evaluate the biostimulant activity of these fungi by adding either their mycelia (DE: direct effect) or their cell-free filtrates (CFF: indirect effect) to the plant-growth media. The best significant growth stimulation was obtained with plants treated by . However, only the CFFs of (A5.1) and (A8) when added at a dilution factor of 1/50 to half-strength nutritive solution (0.5NS) resulted in significant improvement of all assessed growth parameters. Indeed, the A5.1CFF and A8CFF in 0.5NS induced a significant better increase in the biomass production when compared to NS or 0.5NS alone. All fungi produced indole acetic acid in the CFFs, which could be one of the key factors explaining their biostimulant activities. Furthermore, six genes involved in nitrogen-metabolism ( and ), auxin biosynthesis ( and ), and brassinosteroid biosynthesis ( and ) were shown to be induced in roots or leaves following treatment of plants with the all CFFs. This work opens up a prospect to study in deep the biostimulant activity of PGPFs and their applications to decrease the requirement of chemical fertilizers in the hydroponic growing systems.
水培系统已引起关注，并越来越多地应用于炎热干旱的沙漠地区。水培系统具有诸多益处，比如能够节约用水、提高养分利用效率、易于环境控制以及预防土传病害。然而，营养液中化肥的高消耗量以及封闭水培系统对盐分的敏感性是需要解决的问题。因此，我们研究活动的主要目标是分离促进植物生长的真菌，以开发可持续的水培系统。我们正在致力于分离并测试将促进植物生长真菌（PGPF）的无细胞滤液（CFF）纳入营养液成分的可能性。在这项工作中，我们从盐生草的根际分离出了六株促进植物生长真菌。通过ITS1和ITS4引物扩增的DNA序列的系统发育分析将分离出的真菌鉴定为： ， ， ， ， ，和 。通过向植物生长培养基中添加这些真菌的菌丝体（DE：直接效应）或无细胞滤液（CFF：间接效应），以烟草幼苗活力的提升作为标准来评估这些真菌的生物刺激活性。用 处理过的植物获得了最显著的生长刺激。然而，只有 （A5.1）和 （A8）的无细胞滤液以1/50的稀释倍数添加到半强度营养液（0.5NS）中时，才导致所有评估的生长参数都有显著改善。事实上，与单独的NS或0.5NS相比，0.5NS中的A5.1CFF和A8CFF在生物量生产上诱导出显著更好的增加。所有真菌在无细胞滤液中都产生了吲哚乙酸，这可能是解释它们生物刺激活性的关键因素之一。此外，在用所有无细胞滤液处理植物后，参与氮代谢（ 和 ）、生长素生物合成（ 和 ）以及油菜素甾体生物合成（ 和 ）的六个基因在根或叶中被诱导表达。这项工作为深入研究促进植物生长真菌的生物刺激活性及其在减少水培种植系统中化肥需求方面的应用开辟了前景。
