Invasive Lactuca serriola seeds contain endophytic bacteria that contribute to drought tolerance

Abstract

The mutualistic relationship between alien plant species and microorganisms is proposed to facilitate or hinder invasive success, depending on whether plants can form novel associations with microorganisms in the introduced habitats. However, this hypothesis has not considered seed endophytes that would move together with plant propagules. Little information is available on the seed endophytic bacteria of invasive species and their effects on plant performance. We isolated the seed endophytic bacteria of a xerophytic invasive plant, Lactuca serriola, and examined their plant growth-promoting traits. In addition, we assessed whether these seed endophytes contributed to plant drought tolerance. Forty-two bacterial species were isolated from seeds, and all of them exhibited at least one plant growth-promoting trait. Kosakonia cowanii occurred in all four tested plant populations and produced a high concentration of exopolysaccharides in media with a highly negative water potential. Notably, applying K. cowanii GG1 to Arabidopsis thaliana stimulated plant growth under drought conditions. It also reduced soil water loss under drought conditions, suggesting bacterial production of exopolysaccharides might contribute to the maintenance of soil water content. These results imply that invasive plants can disperse along with beneficial bacterial symbionts, which potentially improve plant fitness and help to establish alien plant species.

Seed Endophytic Bacteria of Pearl Millet (Pennisetum glaucum L.) Promote Seedling Development and Defend Against a Fungal Phytopathogen

“…In this study, KAS1 was found to be the most dominant isolate since it was most frequently isolated from seeds of millet followed by KAS4 ( Table 1 ). Recently, a study reported the occurrence of Kosakonia cowanii as the most common SEB in seeds of Lactuca serriola ( Jeong et al, 2021 ). Pantoea and Bacillus spp.…”

“…In both trials, we found that isolates KAS1, and KAS4 significantly increased the root-shoot lengths, biomass, and photosynthetic pigments in seedlings, and both isolates were the highest producers of IAA and the best P solubilizers ( Table 2 ). Kosakonia cowanii and Pantoea species have been reported as seed vectored bacteria in many crop seeds with plant-growth promoting activities ( Chimwamurombe et al, 2016 ; Verma et al, 2017 ; Jeong et al, 2021 ). The profound effect of KAS1 and KAS4 treatment on root architecture development of seedlings may be because of their IAA activities.…”

Cultivable Endophytic Bacteria in Seeds of Dongxiang Wild Rice and Their Role in Plant-Growth Promotion

“…For example, Khalaf et al [22] reported that Bacillus and Paenibacillus isolated from cucurbit seeds emit volatile organic compounds (VOCs) and secrete extracellular ribonucleases which could suppress fungal pathogens. Jeong et al [23] observed that the colonization of seed endophytic bacterium Kosakonia cowanii GG1 into Arabidopsis thaliana resulted in the stimulation of plant growth under drought conditions. Xu et al [24] found a seed-borne Bacillus strain that improved the root and shoot growth of tomato, probably through the production of ACC deaminase and nitrogen fixation.…”

Variation of the seed endophytic bacteria among plant populations and their plant growth‐promoting activities in a wild mustard plant species, Capsella bursa‐pastoris

“…However, the ecological significance of SEB in weedy species has gained attention just recently. For instance, SEB can contribute to the seed germination and growth in invasive Phragmites australis (White et al, 2018 ), drought resistance in Lactuca serriola (Jeong et al, 2021 ), and the competitive ability by antagonistic effects on the competitor species (Elmore et al, 2019 ). Although soil microbiome has been postulated as a major source of mutualistic microorganisms for weedy plant species (Trognitz et al, 2016 ), our results imply that SEB might be another source of mutualistic microorganisms.…”

“…Despite their plausible ecological significance (Elmore et al, 2019 ; Jeong et al, 2021 ; White et al, 2018 ), relatively little information is available on the characteristics of SEB in weed plant species. Most information on the SEB has come from studies using agriculturally important crop plants (Card et al, 2015 ; Pal et al, 2019 ; Shahzad et al, 2018 ).…”