Bacterial endophytes of mangrove propagules elicit early establishment of the natural host and promote growth of cereal crops under salt stress

Abstract

Mangroves, dominating tropical intertidal zones and estuaries, are among the most salt tolerant plants, and propagate through reproductive units called propagules. Similarly to other plants' seeds, propagules may harbor beneficial bacteria. Our hypothesis was that mangroves, being able to grow into seawater, should harbor bacteria able to interact with the host and to exert positive effects under salt stress, which could be exploited to improve crop production. Therefore, we isolated bacterial endophytes from mangrove propagules with the aim to test whether these bacteria have a beneficial potential on their natural host and on different crops like barley and rice, cultivated under salt stress. The 172 bacterial isolates obtained were screened for plant growth promotion (PGP) activities in vitro, and the 12 most promising isolates were tested on barley under non-axenic conditions and salt stress. Gordonia terrae KMP456-M40 was the best performing isolate, increasing ear weight by 65%. Basing on the in vivo PGP activity and the root colonization ability, investigated by fluorescence in situ hybridization and confocal microscopy, three strains were additionally tested on mangrove propagule germination and on rice growth. The most effective strain was again G. terrae KMP456-M40, which enhanced the root length of mangrove seedlings and the biomass of salt-stressed rice under axenic conditions up to 65% and 62%, respectively. We demonstrated that propagules, the reproductive units of mangroves, host beneficial bacteria that enhance the potential of mangrove seedlings establishment and confer salt tolerance to cereal crops.

Unveiling the Microbiota Diversity of the Xerophyte Argania spinosa L. Skeels Root System and Residuesphere

“…4d , Supplementary Table 3 ). The bacteria affiliated to these taxa were widely reported as plant growth–promoting bacteria selected in the root endosphere and/or rhizosphere by a range of different plant species under extreme conditions such as soil salinity and water scarcity [ 14 , 16 ]. Extremophilic EPS-producing bacteria isolated from desert and saline systems were able to produce biosurfactants/bioemulsifiers that under controlled laboratory conditions proved to increase water retention of a sandy soil [ 78 ], an aspect of great interest to reverse desertification.…”

“…Plant growth and adaptation to the environmental conditions are strongly supported by the plant microbiome [10]. In the past years, extremophilic plants and their associated microbiota have been largely studied [11][12][13] aiming at the exploitation of beneficial microbe-plant interactions to boost plant growth and productivity under harsh conditions such as soil salinity [14][15][16][17] and water shortage [18][19][20][21][22]. In this framework, experimental protocols have been established in the last years to effectively combine plant seeds and extremophilic microbes that are able to cope with desiccation and to promote the plant growth under drought conditions [23].…”

Hydrolytic Profile of the Culturable Gut Bacterial Community Associated With Hermetia illucens

“…Total DNA from each isolate was extracted by boiling lysis (Ferjani et al, 2015) or using a phenol-chloroform DNA extraction based protocol (Sambrook et al, 1989) in case of 16S rRNA PCR amplification failure on bacterial DNA extracted according to boiling lysis. The bacterial collection was dereplicated by ITS-PCR fingerprinting using the primer pair ITS-F (5 -GTC GTA ACA AGG TAG CCG TA-3 ) and ITS-Reub (5 -GCC AAG GCA TCC ACC-3 ) (Mapelli et al, 2013;Soldan et al, 2019). For each ITS group one/two candidates were selected and the 16S rRNA gene was amplified using the primers 27F (5 -AGA GTT TGA TCM TGG CTC AG -3 ) and 1492R (5 -CTA CGG CTA CCT TGT TAC GA -3 ) (Mapelli et al, 2013;Soldan et al, 2019).…”

“…The bacterial collection was dereplicated by ITS-PCR fingerprinting using the primer pair ITS-F (5 -GTC GTA ACA AGG TAG CCG TA-3 ) and ITS-Reub (5 -GCC AAG GCA TCC ACC-3 ) (Mapelli et al, 2013;Soldan et al, 2019). For each ITS group one/two candidates were selected and the 16S rRNA gene was amplified using the primers 27F (5 -AGA GTT TGA TCM TGG CTC AG -3 ) and 1492R (5 -CTA CGG CTA CCT TGT TAC GA -3 ) (Mapelli et al, 2013;Soldan et al, 2019). PCR fragments were partially sequenced at Macrogen (South Korea) and sequences were then aligned against the EzBioCloud database (Yoon et al, 2017).…”

Characterization of salt-tolerant plant growth-promoting rhizobacteria and the effect on growth and yield of saline-affected rice

“…This group of rhizospheric bacteria could effectively colonize plant roots and maintains soil fertility by offering a favourable alternative to inorganic fertilizers and pesticides [6]. The effectiveness of PGPR to increase the growth of various crops under salt stress conditions have been reported previously [7,8]. The preliminary selection of locally-isolated salt-tolerant PGPR for salinity mitigation is crucial to ensure the effectiveness, and it has been reported that the indigenous strains are more efficient in boosting plant resistance to salinity stress compared to PGPR originated from the non-saline ecosystem [9,10].…”