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

Abstract

Seed-borne pathogens in crops reduce the seed germination rate and hamper seedling growth, leading to significant yield loss. Due to the growing concerns about environmental damage and the development of resistance to agrochemicals among pathogen populations, there is a strong demand for eco-friendly alternatives to synthetic chemicals in agriculture. It has been well established during the last few decades that plant seeds harbor diverse microbes, some of which are vertically transmitted and important for plant health and productivity. In this study, we isolated culturable endophytic bacteria and fungi from soybean seeds and evaluated their antagonistic activities against common bacterial and fungal seed-borne pathogens of soybean. A total of 87 bacterial isolates and 66 fungal isolates were obtained. Sequencing of 16S rDNA and internal transcribed spacer amplicon showed that these isolates correspond to 30 and 15 different species of bacteria and fungi, respectively. Our antibacterial and antifungal activity assay showed that four fungal species and nine bacterial species have the potential to suppress the growth of at least one seed-borne pathogen tested in the study. Among them, Pseudomonas koreensis appears to have strong antagonistic activities across all the pathogens. Our collection of soybean seed endophytes would be a valuable resource not only for studying biology and ecology of seed endophytes but also for practical deployment of seed endophytes toward crop protection.

Endophytic fungi of soybean (Glycine max (L.) Merr.) and their potential applications

“…Fungal endophyte genera such as Cladosporium, Alternaria, Diaporthe, and Epicoccum were isolated previously from soybean stems (Impullitti and Malvick 2013). In addition, Kim et al (2022) reported that culturable endophyte microbes that inhabit soybean seeds may have a potential role for inhibiting seed-borne pathogens. They also suggested that fungal endophytes isolated from soybean seeds, such as Alternaria hungarica and Clasdosporium pseudocladosporioides, have suppressive effects against seed-borne pathogens.…”

“…Introduction of Paraburkholderia phytofirmans PsJN to wheat showed changes in seed microbiome composition and plant growth traits (Mitter et al 2017). During the stages from seed germination to seedling, seed endophytes are the first to associate with plants before other microbial invasions from the soil (Kim et al 2022). Johnston-Monje et al (2021) recently proved that both seedtransmitted bacteria and fungi can have a long-term effect on crop microbiome structure affecting plant growth, health, and productivity.…”

“…Johnston-Monje et al (2021) recently proved that both seedtransmitted bacteria and fungi can have a long-term effect on crop microbiome structure affecting plant growth, health, and productivity. Over the recent years, several scientific studies have been conducted to investigate the origin and diversity and to understand the potential of endophytic microbes of seeds (Nelson 2018;Compant et al 2019;Bziuk et al 2021;Johnston-Monje et al 2021;Kim and Lee 2021;Kim et al 2022). However, the studies on fungal endophytes on soybean seeds are very limited.…”

Implications of Domestication in Theobroma Cacao L. Seed-borne Microbial Endophytes Diversity

“…Recent data on multiple cultivated species indicate that the seed microbiota would constitute most cultivated plants' microbial populations [17]. The study of seed-borne endophytes has focused on shortcycle crops (e.g., maize, soybean, rice) where the effect of endophytes on establishment, growth, and resistance to stresses has been evaluated [26] [27][28] [29]. For tropical perennial plants, studies on the association and interaction of plants and seed-borne microbiota are still incipient.…”

Colonization ofBacillus altitudinison the Compatible Soybean Varieties to Provide Seed Rot Resistance

“…Current studies on the soybean seed microbiome indicated lower diversity compared to rhizosphere and phyllosphere microbiomes [34]. Using culture-dependent and culture-independent methods, 22 and 27 bacterial genera were identified in the soybean seed microbiome, respectively [35, 36]. Among these seed-associated microbes, Bacillus , Pantoea , and Sphingomonas were identified as the most dominant genera in soybean seeds [36], and some of these seed-associated bacteria exhibited in vitro antagonistic activity against various soybean pathogens [35].…”