Development of ACCd producer mutant and the effect of inoculation on red pepper plants.

is a plant-growth-promoting bacterium capable of colonizing and promoting growth in numerous crops of agronomic and horticultural significance. The objective of the present study is to develop CW903- flocculating cells and to test their performance in promoting the growth of red pepper plants grown under salt stress. The flocculating CW903-S recorded 12.6, 37.3 and 91.6% higher ACCd activity at 50, 100 and 150 mM NaCl concentrations, respectively, compared to non-flocculating (normal) CW903- cells. The flocculating CW903-S recorded 29.8 and 24.5% higher specific growth rates compared to non-flocculating CW903- cells at 100 and 150 mM NaCl concentration, respectively. The flocculating CW903-S recorded 29.7 and 24.5% higher production of IAA-like molecule compared to the non-flocculating CW903-S at 100 and 150 mM NaCl concentration, respectively. Similarly, 27.5 and 25.7% higher ARA activity was observed with the flocculating CW903-S compared to the non-flocculating CW903-S type cells at 100 and 150 mM NaCl concentration, respectively. In the pot culture experiment at 50 and 100 mM NaCl concentration, CW903-S inoculated pepper plants recorded 9.4 and 4.7% less ethylene emission, when compared to plants inoculated with non-flocculating CW903-S cells. At 100 mM NaCl concentration, plants inoculated with flocculating CW903-S recorded 27.5% higher dry weight compared to plants inoculated with non-flocculating CW903-S cells. This study implied the significance of flocculating CW903-S with better stress amelioration and plant growth promotion in red pepper plants grown under salt-affected conditions due to the positive influence of ACCd activity.