**3.3 Plant growth promotion by bacterial isolates antagonistic to** *X. oryzae* **pv.** *oryzae*

Based on the growth inhibition of *X. oryzae* pv. *oryzae* by these antagonistic bacterial species*,* 32 bacterial isolates were selected for plant growth promotion assay and for subsequent assessment of their net house and field performances. Different plant growth promoting bacterial antagonists enhanced the root length, shoot length and vigor index at 14, 21 and 28 DAS (**Table 6**). Among 32 bacterial

#### **Figure 4.**

*Representative photographs showing the assessment of different plant growth promoting determinants. Siderophore production: antagonistic bacterial isolates showed positive siderophore production activity as indicated by orange halo zone around bacterial colony on CAS agar plates, phosphate solubilization: antagonistic bacterial isolates showed positive phosphate solubilizing activity by producing clear halo zone around the bacterial colony on National Botanical Research Institute's Phosphate (NBRIP) agar plates and indole acetic acid (IAA) production: IAA activity by different antagonistic bacterial isolatesindicated by the presence of pink color when bacterial culture supernatant mixed with Salkowskis reagent. BDISOB05P: isolate from Mymensingh.*


#### *Potential Role of Rice Plant Growth Promoting Phylloplane and Rhizospheric Bacteria… DOI: http://dx.doi.org/10.5772/intechopen.99854*


#### *Integrative Advances in Rice Research*

**Table 6.**

 *Effect of different antagonistic bacteria on plant growth promotion of rice (cv. IR24).*

*Potential Role of Rice Plant Growth Promoting Phylloplane and Rhizospheric Bacteria… DOI: http://dx.doi.org/10.5772/intechopen.99854*

isolates, the maximum vigor index (4198.29) was recorded in seedlings raised from seeds treated with BDISOB45PanR (*Bacillus paramycoides*) followed by BDISOB283R (*Pseudomonas fluorescens*) (4087.60), BDISOB222R (*P. plecoglossicida*) (4040.97) while the minimum (2418.03) vigor index was obtained in BDISOB135SheR (*Bacillus* sp.) followed by BDISOBP (*S. marcescens*) (2449.53) and BDISOB54R (*B. gladioli*) (2449.53) at 30 DAS. However, all the antagonistic bacterial isolates exhibited the increase of vigor index ranged by 0.01 to 71.41. This result implies that some of the selected antagonistic bacterial isolates have the potentiality in enhancing plant growth.

## **3.4 Plant growth promotion by different bacterial isolates antagonistic to** *Xanthomonasoryzae* **pv.** *oryzae*
