Table 2.
Attributes of rhizobia exerted against abiotic stress on host plants/in vitro
| Rhizobia | Crop species | Screening medium | Growth condition | Remarks | References | |
|---|---|---|---|---|---|---|
| Drought stress | ||||||
| R. tropici co-inoculated with Paenibacillus polymyxa | Kidney bean | −7, −70 and <−85 kPa | Greenhouse | Enhanced plant height, shoot dry weight and nodule number | Figueiredo et al. (2008) | |
| Bradyrhizobium sp. | – | PEG 6000 induced | In vitro and pot culture |
Enhanced drought tolerance, IAA and EPS production; nodulation, nodule ARA, nodule N |
Uma et al. (2013) | |
| M. mediterraneum LILM10 | Chickpea | – | Field study |
Increased nodule number, shoot dry weight and grain yield Water deficient tolerant strains were also NaCl tolerant. |
Romdhane et al. (2009) | |
| R. elti (engineered for enhanced trehalose-6-phosphate synthase) | Kidney bean | – | Pot studies |
Enhanced nodules, nitrogenase activity and biomass production Higher tolerance than wild type strains |
Suárez et al. (2008) | |
| Temperature stress | ||||||
| Mesorhizobium spp. | – | 20, 28 and 37 °C | In vitro |
Overproduction of 60 kDa protein by all the isolates All the isolates revealed more tolerance to 20 °C than 37 °C. |
Rodrigues et al. (2006) | |
| Heat shock at 60 °C for 15 min; 46 °C for 3 h | In vitro | Variations in the expression of protein profile | ||||
| Rhizobium sp. DDSS69 | – | 5 °C | In vitro |
Induction of 135 and 119 kDa proteins Variation in the protein profile of stressed and non-stressed cells |
Sardesai and Babu (2001) | |
| Salt/osmotic stress | ||||||
| M. ciceri ch-191 | Chickpea -salt resistant and sensitive cultivars | 50, 75, 100 mM | In vitro |
Decreased plant dry weight, nitrogenase activity in sensitive cultivars Less N2 fixation inhibition, higher root to shoot ratio, normalized nodule weight and shoot K/Na ratio and reduced foliar accumulation of Na + in resistant cultivars |
Tejera et al. (2006) | |
| M. ciceri ch-191 | – | 100–400 mmol NaCl/L | In vitro |
Higher tolerance was noticed on 200 mmol/L Altered protein and LPS levels Higher proline accumulation than glutamate |
Soussi et al. (2001) | |
|
Acacia rhizobia. (40 strains) |
– | 0.4-1.4 M NaCl | In vitro |
Presence of small and large plasmids Intracellular accumulation of free glutamate Three rhizobia strains has tolerated 1.4 M NaCl |
Gal and Choi (2003) | |
| M. ciceri, M. mediterraneum and S. medicae | Chickpea | 25 mM NaCl | Glasshouse |
M. ciceri enhanced the nodulation and CAT activity Least decrease in nodule protein and SOD activity |
Mhadhbi et al. (2004) | |
| Rhizobia strains | Lentil | 5.5 Ds m−1 | Field study | Increased plant biomass, nodule number and nodule dry weight | Islam et al. (2013) | |
| M. ciceri, M. mediterraneum | Chickpea | Mannitol—50 mM induced | Aerated hydroponic cultures |
Maintenance of growth and nitrogen fixing activity Increased antioxidant enzyme activity in nodules |
Mhadhbi et al. (2008) | |
| pH stress | ||||||
| Mesorhizobium spp. | – | 5, 7 and 9 | In vitro | Large range of isolate variation in growth at pH 7/9 and others at pH 5/7 | Rodrigues et al. (2006) | |