Screening of Rice Endophytic Biofertilizers with Fungicide Tolerance and Plant Growth-Promoting Characteristics

Abstract

The application of pesticides is unavoidable in conventional agricultural practice. To develop effective biofertilizers, bacterial strains with both pesticide tolerance and plant growth-promoting (PGP) traits were isolated for further testing. Seedlings of rice (Oryza sativa) were planted in soil with 1, 5, or 10 times the recommended rates of the fungicides etridiazole, metalaxyl, and tricyclazole. Endophytic bacteria were isolated from roots of rice seedlings. The bacterial 16S rDNA sequences and related PGP characteristics including potential nitrogen fixation, phosphorus-solubilizing and indole acetic acid (IAA) production ability were further examined. In all, 17 different strains were obtained from rice seedling roots; five strains with both nitrogen fixation potential and IAA production ability included Rhizobium larrymoorei E2, Bacillus aryabhattai E7, Bacillus aryabhattai MN1, Pseudomonas granadensis T6, and Bacillus fortis T9. Except for T9, all strains could tolerate two or more fungicides. We inoculated rice roots with the endophytic bacteria and all conferred rice growth-promoting ability. Bacillus aryabhattai MN1 was further tested and showed high tryptophan dose-dependent IAA production ability, tolerance towards etridiazole and metalaxyl application and should be considered a potential bacterial biofertilizer.

Elucidating Mechanisms of Endophytes Used in Plant Protection and Other Bioactivities With Multifunctional Prospects

“…Having a better understanding of the diverse roles microorganisms play in the ecosystem will enhance the ways they can be applied in the field of agriculture most importantly for plant growth and crop yield (Nair and Padmavathy, 2014). The world of endophytes has attracted the interest of many researchers due to their significant roles in promoting growth and in enhancing the survival of plants under extreme conditions (Shen et al, 2019). Bioactive metabolites secreted by endophytic microorganisms are useful in industries, agriculture, and the field of medicine.…”

“…They gain entrance into the seed, leaf, stem, and root of a plant and they are not harmful to the host plant (Yadav, 2018). Endophytes improve plant growth by secreting phytohormones and consequently help in nutrition improvement using bidirectional nutrient transfer and enhancement of the health of plants by protecting them against phytopathogens (Andreozzi et al, 2019;Shen et al, 2019). Plant-endophyte interaction triggers the protection of plants against harmful conditions of the environment such as heavy metal presence and drought (Khan et al, 2019;Kushwaha et al, 2019).…”

“…Endophytes are numerous and studies have it that they are present in many plants; they became important due to their capacity to produce many bioactive metabolites and biotechnologically relevant enzymes (Khan et al, 2014;Rajamanikyam et al, 2017). Most times when endophytes are inoculated in the plant, they produce significant biomass increment and also help in boosting commercial agriculture (Santoyo et al, 2016;Shen et al, 2019). Endophytes are gaining biotechnological and industrially relevance as a result of their ability to secrete secondary metabolites, serve as biocontrol agents, antimicrobial agents, antitumor agents, and immunosuppressants, and to secrete antiviral compounds and development of natural antioxidants, antidiabetic agents, antibiotics, and insecticidal products (Gouda et al, 2016;Yadav, 2018).…”

Diversidade, mecanismos de atuação e potencial agrícola de bactérias promotoras de crescimento de plantas, usando milho como cultura exemplo

“…Entre os mecanismos de promoção de crescimento vegetal por bactérias podem ser incluídos: facilita a absorção de nutrientes pelas plantas (SOUSA et al, 2016;GRANADA et al, 2018;ROTARU;RISNOVEANU, 2019;OLIVEIRA-LONGATTI et al, 2020); altera a disponibilidade e a toxicidade de metais às plantas (WOOD et al, 2016); protege as plantas pela indução na produção de fito-hormônios, como os ácidos salicílico e jasmônico (LIAN et al, 2000;MCCUE et al, 2000;GUTJAHR;PASZKOWSKI, 2009;DAR et al, 2015); aumenta o sistema radicular com a produção de ácido indolacético (PUENTE et al, 2019;SHEN et al, 2019;VALDEZ-NUÑEZ et al, 2019;PURI; PADDA; CHANWAY, 2020); auxilia nos processos como a Sideróforos são moléculas secretadas por micro-organismos que atuam na solubilização deste ferro no solo, pela sua alta afinidade a este nutriente. Estas moléculas se ligam a receptores específicos e são ativamente transportadas através da membrana celular de bactérias (SANTOS et al, 2018), e são frequentemente liberadas por BPCPs (JI; GURURANI; CHUN, 2014;SULOCHANA et al, 2014).…”

“…Além disso, resultados positivos foram obtidos com a utilização de isolados produtores de AIA nas culturas de milho (PEREZ-MONTANO et al, 2014;KUAN et al, 2016;BATISTA et al, 2018;IKEDA et al, 2020), arroz (HAHN et al, 2016THEISEN et al, 2017;SHEN et al, 2019), trigo (BARNAWAL et al, 2017PATEL;ARCHANA, 2017;EMAMI et al, 2019), Oliveira (SILVA et al, 2017BIZOS et al, 2020) e soja (CASSÁN et al, 2009;THEISEN et al, 2017;PUENTE et al, 2018;ARMENDARIZ et al, 2019;IGIEHON;BABALOLA;AREMU, 2019;PUENTE et al, 2019). Novamente, este largo espectro indica a grande importância potencial destes micro-organismos na promoção de uma agricultura mais sustentável.…”