MSc

The study entitled “Isolation and characterization of Pink Pigmented Facultative Methylotrophs (PPFMs) associated with paddy” was conducted in the Department of Agricultural Microbiology, College of Agriculture, Vellayani during the period 2015-2017. The main objectives of the study were isolation, characterization and evaluation of Pink-Pigmented Facultative Methylotrophs (PPFMs) associated with paddy for antagonistic efficiency, seed germination, seedling growth and yield of paddy. .
The pink pigmented facultative methylobacteria (PPFM) were isolated from phyllosphere of paddy collected from different locations of Kerala by leaf imprint method on Ammonium Mineral Salt (AMS) agar medium supplemented with 0.5% methanol and cycloheximide. Forty six isolates were obtained from different locations and code numbers were allotted for each of the isolate. They were tentatively identified as PPFMs based on the characteristic pink pigmented colonies on AMS agar supplemented with 0.5% methanol as sole source of carbon and energy. The product developed by Tamil Nadu Agricultural University was taken as the reference culture.
Indole Acetic Acid production by the different isolates of PPFM showed wide variations ranging from 9.27 to 68.65 μg mL-1 of culture filtrate. Maximum IAA production of 68.65μg mL-1 of culture filtrate was recorded by PPFM35. The reference culture produced 57.39 μg mL-1 of IAA.
All the isolates were found to produce carotenoid pigment in varied quantity ranging from 0.07 to 1.74 μg mL-1. Among these isolates, the highest carotenoid production was recorded in PPFM16 (1.74 μg mL-1). The reference culture recorded a total carotenoid production of 0.64 μg mL-1.
The antagonistic efficiency of all forty seven PPFM isolates including reference culture was assessed against two important fungal pathogens of paddy namely, Rhizoctonia solani, Pyricularia oryzae and one bacterial pathogen, Xanthomonas oryzae pv. oryzae following dual culture method. Six out of forty seven isolates tested inhibited Rhizoctonia solani. The results revealed that the isolate PPFM 10 exhibited the maximum zone of inhibition (ZOI) of 12.72 mm. The reference culture inhibited Rhizoctonia solani and produced a ZOI of 9.07mm. Four out of forty seven isolates tested showed antagonistic activity against Pyricularia oryzae with PPFM24 producing the maximum zone of inhibition of 10.00 mm. Four out of forty seven isolates tested inhibited Xanthomonas oryzae pv. oryzae and PPFM5 produced the maximum ZOI of 9.80 mm diameter.
In the study on the effect of PPFM isolates on seed germination and seedling growth both treated and uninoculated control seeds germinated on the second day of seed treatment. Maximum germination percentage of 100 was recorded in seeds treated with PPFM35. Treatment with PPFM30 recorded the maximum shoot length of 26.38 cm and maximum root length of 24.20 cm was obtained in seeds treated with PPFM22 and same isolate recorded the highest seedling vigour index of 4756.35 over the control (3037.91). The root shoot ratio of seedlings showed significant increase when seeds were treated with PPFM isolates. Maximum root shoot ratio of 0.62 was observed when seeds were treated with PPFM26 and PPFM35 compared to control (0.33).
A pot culture experiment was conducted using variety Jyothi (Ptb-39)) in completely randomized design using wetland soil. Seedlings were dipped in 2 per cent of liquid culture of the PPFM isolates before transplanting. One per cent foliar spray of the liquid culture of respective isolates was given 15 and 30 days after transplanting. Appropriate control treatments and replications were maintained. Application of PPFM isolates significantly increased growth and biomass production.
Also the yield of paddy was significantly increased. PPFM11 recorded the highest grain yield of 46.30 g hill-1 whereas the control recorded a grain yield of 33.65 g hill-1 only. The reference culture recorded a grain yield of 38.40 g hill-1. Physiological characterization of plants revealed significant influence of PPFM isolates on chlorophyll content, cell membrane stability and proline content of the plant compared to untreated plants.
The isolates PPFM11, PPFM16, PPF19, PPFM22 and PPFM35 were adjudged as superior isolates based on maximum germination percentage, seedling vigour index, growth promotion efficacy and grain yield of paddy. These five isolates were identified as Methylobacterium spp. based on morphological, biochemical and molecular characteristics.