*2.2.1 Production of antibiotics*

*Legume Crops - Prospects, Production and Uses*

*Bacillus subtilis* LDR2 *Trigonella* 

*Pseudomonas fluorescens*

TDK1

*Pseudomonas aeruginosa* GGRJ21

*Arthrobacter protophormiae* SA3

*Ochrobactrum pseudogrignonense* RJ12*, Pseudomonas* sp. RJ15 and *B. subtilis* RJ46

**Microorganism Plant host Abiotic** 

*Arachis hypogea*

*foenumgraecum*

*Pisum sativum*

*Vigna mungo* and *P. sativum*

In general, plants can benefit in many ways, thanks to the production of siderophores since they are also involved in the improvement of nitrogen fixation or in the prevention of toxicity by heavy metals [75]. Thus, PGPR able to produce siderophores have a certain competitive advantage over other microorganisms in the rhizosphere [64]. Some of these microorganisms are shown in **Table 3** showing the repercussions caused by the synthesis of iron chelating compounds depending on

*Beneficial interactions between bacteria that produce siderophores and legumes and plant improvements under* 

**Microorganism Plant host Plant improvement Abiotic** 

*Beneficial interactions between ACC deaminase producing bacteria and legumes under stress conditions.*

**stress**

Salinity Improved plant growth

osmolytes

Drought Alleviated ethylene-induced damage and improved nodulation and mycorrhizal fungi colonization

Salinity Alleviated ethylene-induced damage and improved nodulation and mycorrhizal fungi colonization

Drought Increased seed germination,

plant biomass, chlorophyll, and relative water content.

stress

*V. radiata* Drought Increased plant biomass, the

*V. radiata* Reduction of Ni and Zn

*G. max* Positive effects in photosynthesis and mineral nutrients

concentrations in plant tissues

chlorophyll content, and reduction of fungal infections

Higher growth and yield Drought [74]

**stress**

**Benefits for plants References**

[67]

[68]

[69]

[70]

[71]

parameters and alleviated saline

relative water content, and

Heavy metals

Heavy metals

Salinity [73]

**References**

[58]

[72]

Indirect mechanisms are those processes where PGPR prevent or neutralize the harmful action of phytopathogens by the production of substances that confer

the crop and the conditions of the plant-microbe interaction.

*P. aeruginosa* GS-33 *G. max* Improve plant biomass,

*Cicer arietinum*

**120**

**2.2 Indirect mechanisms**

*Bradyrhizobium* sp.

*Bradyrhizobium* sp.

*Pseudomonas putida* NBRIRA and *Bacillus amyloliquefaciens* NBRISN13

RM8

**Table 2.**

YL6

**Table 3.**

*stress conditions.*

Antibiotic production is the main mechanism by which a large and heterogeneous group of bacteria fight the harmful effects of plant pathogens (usually fungi). The antibiotics produced by PGPR are low molecular weight compounds that negatively interfere with the metabolic processes of other microorganisms, thus delaying their growth [64] or inhibiting it [56]. There are some examples of PGPR that produce antibiotics against phytopathogens reflected in **Table 4**.

The effectiveness with which these molecules interfere with pathogen suppression will depend on the metabolite secreted by the PGPR and environmental conditions (mineral content of the soil, osmotic conditions, carbon sources, etc.) [76]. Moreover, some phytopathogens may develop resistance to specific antibiotics by repeated use of the same strain that produces a particular antibiotic, so it is preferable to inoculate plants with PGPR that produce several antibiotics [59]. There are some PGPR that have antagonistic activities against some phytopathogens in addition to improve plant growth in the presence of some stress as it is the case of *Cellulosimicrobium funkei* AR6 that improves the root elongation in crops of *P. vulgare*, *V. radiata,* and *V. mungo* in the presence of Cr(VI) and also has a strong antagonistic activity against *Aspergillus niger* [77]. Another example is *B. thuringiensis* UFGS2 that improves plant growth, physiologic parameters, and the resistance of the soybean against *S. sclerotiorum* under drought stress [78].
