THE APPLICATION OF PLANT GROWTH PROMOTING RHIZOBACTERIA AS BIOFERTILIZER FOR CEREAL CROPS (WHEAT, RICE AND MAIZE) OF DISTRICT SWAT, KHYBER PAKHTUNKHWA, PAKISTAN

Abstract

The present study was conducted to isolate and characterize Plant Growth Promoting Rhizobacteria (PGPR) from the rhizosphere of cereal crops at Swat and to assess their impact on plant growth when used as inoculants. A total of 18 bacterial strains were isolated from roots and rhizosphere of cereal crops. On the basis of colony and cell morphology, 4 strains were identified as Azospirillum, 11 as Pseudomonas strains and three strains remained un-identified. With the exception of 3 strains, all isolates showed IAA production in pure culture. Three bacterial strains (Azospirillum brasilense strain R1, Azospirillum lipoferum strain RSWT1 and Pseudomonas strain Ky1) were used to inoculate two varieties of wheat (Inqilab 91 and Fakhre Sarhad), two varieties of rice (Fakhre Malakand and JP 5) and one variety of maize (Pahari) at two experimental sites in Swat (ARIN Mingora and Udigram). Among the bacterial strains tested in the present study, Azospirillum brasilense strain R1 was more effective in plant growth promotion than other strains for both wheat and rice varieties. Azospirillum lipoferum strain RSWT1 showed more positive response than other strains on the yield and growth of maize variety Pahari. The plant height of wheat variety Inqilab 91 was significantly increase up to 18.5 % with Azospirillum brasilense strain R1 as compared to non-inoculated control ones. The increase in plant height with Azospirillum lipoferum strain RSWT1 was 14.7 % and with Pseudomonas Ky1 9.6 %. The number of grains/spike, root and shoot weight and biological yield of the plants inoculated with Azospirillum brasilense strain R1, Azospirillum lipoferum strain RSWT1 and Pseudomonas Ky1 were significantly greater as compared to control treatment. In case of wheat variety Fakhre Sarhad, the inoculation strains also showed positive effects on the growth and yield. At ARIN Mingora, Swat, inoculation of rice variety Fakre Malakand with Azospirillum brasilense strain R1 increased the straw weight by 16.6 %, grain weight by 22.7 % over control. Inoculation of rice variety JP 5 with Azospirillum brasilense strain R1 showed 19 % increase in the straw weight and 39.5 % increase in the grain weight. At this experimental site, inoculation with Azospirillum lipoferum strain RSWT1 and Pseudomonas strain Ky1 increased grain weight by 4.8 – 13.5 % and 17.3 –18.5 % respectively of the rice varieties Fakre Malakand and JP5. At Udigram, Swat, inoculation of rice variety Fakre Malakand with Azospirillum brasilense strain R1 increased the straw weight by 14.2 % and grain weight by 22 % over control. In the rice variety JP 5, any significant beneficial effect of inoculation with Azospirillum lipoferum strain RSWT1 and Pseudomonas strain Ky1 was not observed whereas inoculation with Azospirillum brasilense strain R1 showed positive results of 15.5 % and 27.4 % increase over control in straw weight and grain weight respectively. The rice variety JP 5 was more responsive to the inoculated strains than rice variety Fakre Malakand. In case Of maize variety Pahari, plant height was significantly increase up to 8.82 % with Azospirillum lipoferum strain RSWT1 and with Azospirillum brasilense strain R1 up to 6.52% as compared to non-inoculated control ones. The number of ears/plant, number of grains/ear, number of leaves/plant and stem thickness and 1000 grain weight were significantly affected by bacterial inoculation.