Co-application of Acinetobacter calcoaceticus and L-tryptophan enhances growth, physiology, and yield in bitter gourd.

Plant growth-promoting rhizobacteria (PGPRs) are reported for increasing agricultural productivity and maintaining soil health via different growth-promoting mechanisms. The synergistic application of these PGPRs in combination with plant growth regulators (PGRs) yields more plant growth and yield. Bitter gourd is a vine rich in vitamins, minerals, antioxidants and dietary fiber, and consumed as vegetable for its medicinal benefits. This research was conducted to investigate the effects of individual and co-application of PGPR (Acinetobacter calcoaceticus) and L-tryptophan (L-TRP; 10-4 M @ 30 mL pot-1) as a seed coating and soil application at the flowering stage on the growth, physiology, and yield of bitter gourd (Momordica charantia L.). The pot-experiment consisted of 8 treatments and 3 replication each, in a completely randomized design (CRD). The combined soil application of PGPR and L-TRP at the flowering stage of bitter gourd resulted in an increased vine length from 199.67 cm (control) to 293.33 cm (46.91% increase), chlorophyl content from 30.36 to 46.01 (51.55%) (51.55%), phosphorous content 0.41% to 0.62% (78.37%) and potassium content 1.1% to 1.36% (23.64%), root length 12.66 cm to 21.75 cm (71.80%), number of fruits vine-1 5.95 to 9.84 (average) (65.38% increase), fruit weight 40.95 to 75.92 g (85.40%), number of leaves 78.69 to 101.85 (29.43%),photosynthesis rate 1.92 to 2.54 (32.57%), transpiration rate 2.26 to 2.89 (27.88%), and stomatal conductance 125 to 151molm-2 s-1 (20.8%), compared to respective uninoculated controls. We concluded that the co-application of PGPR and L-TRP can increase growth and yield in conjunction with other traits and that the combined application of PGPR and L-TRP demonstrated potential for improving yield in a resource-efficient, and sustainable manner.