Microbial Associates of Apple Rhizosphere and Their Impact on Growth Promotion and Metal Tolerance

Abstract

newline The present study was carried out in Kullu Valley (Himachal Pradesh) India. For this purpose, Three study sites Seobag (urban site) (Lat N32and#730;51.017 Long E077and#730;09.787 1200 m amsl), Khaknal (commercial site) (Lat N32and#730;10.643 Long E077and#730;11.682 1800 m amsl), and Palchan (residential site) (Lat N32and#730;18.624 Long E077and#730;10.369 2400 m amsl) were selected for the detailed study. Assessment of apple orchards of Himachal Pradesh concerning the application of fertilizers, heavy metal load, and nutritional status were done. Analysis of soil physio-chemical properties, enzyme activities and rhizosphere effect of apple rhizospheric region was also done. Assessment of microbial endophytes associated with apple roots were done and percent colonization by endophytes and mycorrhiza were calculated. Characterization of the selected endophytic microbial isolates and their contribution to plant growth and heavy metal tolerance was also assessed. This study concludes that the orchards soil microbial activities along with altitudinal and seasonal variation studied herein showed several trends as a result of different factors. The soil enzyme activities were mainly affected by the soil physiological parameters and with microbiological interactions. The study further revealed that the positive statistical significance was observed among the site, season and their interactions. Nutrient cycling has also showed significance relation with soil enzyme activities. The overall results of this study can be concluded that substantial addition of major nutrient in apple soil has significantly increased the soil enzymatic activity as well as rhizobacterial ratio. The study further revealed that the rhizobacteria isolated from orchards tree root region performed the plant growth promoting traits, heavy metal tolerance and pesticide tolerance potential. Therefore, these rhicobacteria can be used as a consortium medium to increase the growth of plant and to reduce the application of chemical and synthetic compound.