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

Abstract

Seed endophytic bacteria (SEB) are primary symbionts that play crucial roles in plant growth and development. The present study reports the isolation of seven culturable SEB including Kosakonia cowanii (KAS1), Bacillus subtilis (KAS2), Bacillus tequilensis (KAS3), Pantoea stewartii (KAS4), Paenibacillus dendritiformis (KAS5), Pseudomonas aeruginosa (KAS6), and Bacillus velezensis (KAS7) in pearl millet seeds. All the isolates were characterized for their plant growth promoting activities. Most of the SEB also inhibited the growth of tested fungal phytopathogens in dual plate culture. Removal of these SEB from seeds compromised the growth and development of seedlings, however, re-inoculation with the SEB (Kosakonia cowanii, Pantoea stewartii, and Pseudomonas aeruginosa) restored the growth and development of seedlings significantly. Fluorescence microscopy showed inter and intracellular colonization of SEB in root parenchyma and root hair cells. Lipopeptides were extracted from all three Bacillus spp. which showed strong antifungal activity against tested fungal pathogens. Antifungal lipopeptide genes were also screened in Bacillus spp. After lipopeptide treatment, live-dead staining with fluorescence microscopy along with bright-field and scanning electron microscopy (SEM) revealed structural deformation and cell death in Fusarium mycelia and spores. Furthermore, the development of pores in the membrane and leakages of protoplasmic substances from cells and ultimately death of hyphae and spores were also confirmed. In microcosm assays, treatment of seeds with Bacillus subtilis or application of its lipopeptide alone significantly protected seedlings from Fusarium sp. infection.

Diversity and Exploration of Endophytic Bacilli for the Management of Head Scab (Fusarium graminearum) of Wheat

“…In the current study, three endophytic Bacillus strains ( B. clarus NOK09, B. subtilis NOK33, and B. amyloliquefaciens NOK109) showing maximum bio-control activity against F. graminearum reflected strong character for potassium solubilization and siderophore production. These results are in harmony with earlier reports, where the presence of endophytic bacterial strains showing strong attributes of potassium solubilization and siderophore production were observed [ 67 , 68 , 69 ]. Kushwaha et al [ 15 ] also recorded potassium solubilizing and siderophore-producing traits in endophytic strains of B. cereus , B. amyloliquefaciens, and B. subtilis subsp.…”

Culturable Endophytes Associated with Soybean Seeds and Their Potential for Suppressing Seed-Borne Pathogens

“…Many microbial biological agents have been isolated from diverse environments not limited to soils (Pirttilä et al, 2021;Whipps, 2001). However, only a handful of seed endophytes has been explored for the potential as microbial biological agents for crops (Kumar et al, 2021;Matsumoto et al, 2021). In this work, we isolated seed endophytes of the soybean plant and tested their antagonistic activities against a set of seed-borne pathogens.…”

Dynamic changes in the endophytic bacterial community during maturation of Amorphophallus muelleri seeds

“…Plant endophytes are microorganisms that colonize the internal tissues of plants and are often associated with plants ( Yang et al, 2017 ). Plant endophytes have been found in all plant parts, including roots, stems, leaves, fruits, and seeds ( Kumar et al, 2021 ). They play an important role in each stage of plant development and in plant adaptation to various ecological conditions, making them important to plant growth and health ( Márquez et al, 2007 ; Llorens et al, 2019 ).…”

“…Among them, seed endophytic bacteria have an especially great impact on plant development. Due to positional advantages, endophytic bacteria in seeds may affect plant growth and adaptability from seed germination to seedling formation and continue to affect plant development over time ( Kumar et al, 2021 ). Various seed-borne endophytic bacteria found in plant tissues use direct or indirect mechanisms to improve plant growth and development and enhance plant tolerance to biotic and abiotic stresses ( Santoyo et al, 2016 ; Shahzad et al, 2018 ).…”

“…Specifically, they can promote germination and plant growth by producing auxins and ethylene, mobilizing various nutrients (N, P, K, etc. ), and producing siderophores ( Maheshwari et al, 2019 ; Kumar et al, 2020 , 2021 ; Chang et al, 2021 ); they produce antifungal compounds, toxins, or hydrolytic enzymes to inhibit different plant pathogens to protect plants ( Verma et al, 2019 ); and they indirectly increase plant adaptability by inducing or regulating the expression of plant genes related to growth, development, and defense ( Irizarry and White, 2018 ; Kumar et al, 2021 ). Díaz Herrera et al (2016) reported that the endophytes Paenibacillus sp., Pantoea sp., and Bacillus sp.…”