MSc

Investigation on the effect of plant growth promoting rhizobacteria (PGPR) on growth and yield of bitter gourd was carried out at Department of Olericulture, College of Horticulture, Vellanikkara, during September 2006 to January 2007 under field conditions. High yielding variety Preethi was used for the study.

The study revealed that seeds inoculated with Azospirillum (basal @ 5 kg ha-1 + 40 days after sowing (DAS) @ 5 kg ha-1) recorded early germination (6.48 days) which was followed by the two time application of Pseudomonas flourescens (basal @ 2.5 kg ha-1 + 40 DAS @ 2.5 kg ha-1). The maximum vine length (4.42 m) was recorded in both Bacillus subtilis suspension (108 cfu/ml) @ 2 l/plant application (basal) and Pseudomonas flourescens @ 2.5 kg ha-1. Number of primary branches was maximum (4.80) in plants applied with phosphorous solubilising bacteria (PSB) as basal @ 5 kg/ha and 40 DAS @ 5 kg/ha. Tap root length (23.57 cm) and secondary root length (39.88 cm) were highest in the plants supplied with Azospirillum (basal @ 5 kg ha-1 + 40 DAS @ 5 kg ha-1) where as, dry root weight (4.64 g) was more in case of double application of Bacillus subtilis suspension (108 cfu/ml) basal @ 2 l plant -1 + 40 DAS @ 2 l plant -1.

Control plants were the earliest to flower and fruit. Plants inoculated with basal dose of Bacillus subtilis suspension (108 cfu/ml) produced the highest number of female flowers plant -1 (17.50 flowers) than other treatments. Among the different treatments, double application of Aishwarya (basal @ 30 g plant-1 + 40 DAS @ 30 g plant-1) recorded the highest number of fruits plant -1 (13.60 fruits) and seeds plant -1 (49.33 seeds) respectively which was followed (12.68 fruits and 45.33 seeds) by the inoculation of Pseudomonas flourescens (basal @ 2.5 kg/ha) and Bacillus subtilis suspension (108 cfu/ml) (basal @ 2 l plant -1 + 40 DAS @ 2 l plant -1) respectively. Plants treated with Bacillus subtilis (suspension (108 cfu/ml) basal + 40 DAS @ 2 l plant -1 recorded maximum fruit weight, length and girth (223.49 g, 26.16 cm and 22.93 cm respectively). Flesh thickness (0.73 cm) was highest in double application (basal @ 2 l plant -1 + 40 DAS @ 2 l plant -1) of the Bacillus subtilis, PSB and Aishwarya (basal @ 30 g plant-1+ 40 DAS @ 30 g plant-1) treatments.

There was a highly significant difference between all the treatments under study. Two time application of Bacillus subtilis suspension (108 cfu/ml) basal + 40 DAS @ 2 l plant -1 produced the maximum yield plant -1 and yield plot -1 (2.72 kg and 16.33 kg respectively), which was followed by the single time application of Pseudomonas flourescens as basal @ 2.5 kg ha-1 (2.36 kg ha-1 and 14.19 kg ha-1).

Maximum vitamin C content was recorded in the plants subjected to basal application of Aishwarya @ 30 g plant-1 (138.16 mg/100g) followed by single application of Bacillus subtilis as basal dose. Maximum iron content was recorded (1.89 mg/100g) in plants supplied with Pseudomonas flourescens (basal @ 2.5 kg ha-1 + 40 DAS @ 2.5 kg ha-1). Storage time (4 days) was more for the plants treated with one time application of Bacillus subtilis suspension (108 cfu/ml) @ 2 l plant -1 and Pseudomonas flourescens as basal @ 2.5 kg ha-1.

It can be inferred that inoculation of bitter gourd with plant growth promoting rhizobactreia (PGPR) enhanced its growth, yield and quality attributes. Among the different PGPR studied, Bacillus subtilis suspension (108 cfu/ml) with two time application first as basal @ 2 l plant -1 and second at 40 DAS @ 2 l plant -1 performed best with respect to yield, flower and biometrical characters. The next best treatments were two time application of Aishwarya, Pseudomonas flourescens, Azospirillum and PSB respectively.