Rhizosphere Microbiomes Modulated by Pre-crops Assisted Plants in Defense Against Plant-Parasitic Nematodes

Abstract

Plant-parasitic nematodes cause considerable damage to crop plants. The rhizosphere microbiome can affect invasion and reproductive success of plant-parasitic nematodes, thus affecting plant damage. In this study, we investigated how the transplanted rhizosphere microbiome from different crops affect plant-parasitic nematodes on soybean or tomato, and whether the plant’s own microbiome from the rhizosphere protects it better than the microbiome from fallow soil. Soybean plants growing in sterilized substrate were inoculated with the microbiome extracted from the rhizosphere of soybean, maize, or tomato. Controls were inoculated with extracts from bulk soil, or not inoculated. After the microbiome was established, the root lesion nematode Pratylenchus penetrans was added. Root invasion of P. penetrans was significantly reduced on soybean plants inoculated with the microbiome from maize or soybean compared to tomato or bulk soil, or the uninoculated control. In the analogous experiment with tomato plants inoculated with either P. penetrans or the root knot nematode Meloidogyne incognita, the rhizosphere microbiomes of maize and tomato reduced root invasion by P. penetrans and M. incognita compared to microbiomes from soybean or bulk soil. Reproduction of M. incognita on tomato followed the same trend, and it was best suppressed by the tomato rhizosphere microbiome. In split-root experiments with soybean and tomato plants, a systemic effect of the inoculated rhizosphere microbiomes on root invasion of P. penetrans was shown. Furthermore, some transplanted microbiomes slightly enhanced plant growth compared to uninoculated plants. The microbiomes from maize rhizosphere and bulk soil increased the fresh weights of roots and shoots of soybean plants, and microbiomes from soybean rhizosphere and bulk soil increased the fresh weights of roots and shoots of tomato plants. Nematode invasion did not affect plant growth in these short-term experiments. In conclusion, this study highlights the importance of the rhizosphere microbiome in protecting crops against plant-parasitic nematodes. An effect of pre-crops on the rhizosphere microbiome might be harnessed to enhance the resistance of crops towards plant-parasitic nematodes. However, nematode-suppressive effects of a particular microbiome may not necessarily coincide with improvement of plant growth in the absence of plant-parasitic nematodes.

Plants and Associated Soil Microbiota Cooperatively Suppress Plant-Parasitic Nematodes

“…The importance of the rhizosphere microbiome in plant-nematode interactions has been extensively reviewed (Kerry, 2000;Griffiths et al, 2007;Sikora et al, 2007;Nyaku et al, 2017;. Importantly, some recent studies have demonstrated that the transfer of the rhizosphere microbiome from one crop to another significantly alleviated nematode infection and enhanced the plant resistance to PPN (Elhady et al, 2018;Zhou et al, 2019). This effect depended on the plant species.…”

“…This effect depended on the plant species. The plant's own microbiome protected it better from root invasion of PPN than the bulk soil microbiome or a foreign microbiome, with the notable exception of the highly suppressive maize microbiome (Elhady et al, 2018). Furthermore, Hussain et al (2018) revealed that the same subset of microbial OTU was commonly enriched in the rhizosphere and root endosphere upon nematode challenge in suppressive soil.…”

Microbes Attaching to Endoparasitic Phytonematodes in Soil Trigger Plant Defense Upon Root Penetration by the Nematode

“…Root border cells and root exudates play a crucial role in shaping the microbial communities in the rhizosphere, eventually resulting in a positive plant-soil feedback (Bertin et al, 2003;Bais et al, 2006;Doornbos et al, 2012;De-la-Peña and Loyola-Vargas, 2014;Ma et al, 2017). Evidence is accumulating that certain beneficial microorganisms suppress plant-parasitic nematodes by inducing systemic resistance (ISR) in plants (Reitz et al, 2000;Munif et al, 2001;Siddiqui and Shaukat, 2004;Dababat and Sikora, 2007;Adam et al, 2014b;Selim et al, 2014;Martínez-Medina et al, 2017b;Elhady et al, 2018;Kang et al, 2018;Silva et al, 2018;. In the initial phase of microbially induced plant defense the pattern recognition receptors localized on the plant cell membranes recognize molecular structures on the microbe/ pathogen surface that are referred to as microbe/pathogenassociated molecular patterns (MAMP/PAMP) (Jones and Dangl, 2006).…”

Soil biodiversity and biogeochemical function in managed ecosystems

“…As a result, the rhizosphere supports a marked proliferation and enrichment of specific microorganisms (Jones et al 2009). Beneficial microorganisms associated with plant roots can play an important role in nutrient uptake and plant growth (Gaiero et al 2013), disease suppression (Peralta et al 2018), reducing damage from pests (Elhady et al 2018), and resilience during periods of stress (Gaudin et al 2015). The advent of molecular techniques has facilitated a more comprehensive investigation of biodiversity and function at the root surface.…”