SHIRKOT, C.K.CHANDEL, SHALINI2016-11-152016-11-152016http://krishikosh.egranth.ac.in/handle/1/85603ABSTRACT Apple (Malus domestica Borkh.) is one of the most important fruit crops grown and consumed in the world. In Himachal Pradesh, apple crop occupies an area of 1,07,700 hectare with a production of 7,38,700 metric tons. Attempts to enhance apple productivity, in the Trans Himalayan region has resulted in rapid expansion in area under apple cultivation. However, the strict physio-geographic conditions, pose several hurdles. High yielding modern varieties are being adopted, to increase the productivity, which are highly responsive to external inputs. This results in indiscriminate use of chemical inputs, which poses potential threat to human health and environment. The utilization of plant growth promoting rhizobacteria (PGPR) may help to develop an environmentally benign biological approach for managing fungal diseases and enhancing the plant health resulting in increase in yield. In the last decade of research, several PGPR strains that have been identified and the research on PGPR has seen a tremendous boost, mainly because the role of the rhizosphere as an ecological unit has gained importance in the functioning of the biosphere. The present study envisages better understanding of structural and functional rhizobacterial diversity associated with apple replant sites and root rot infected diseased apple orchards. Principal component analysis revealed detailed insight into correlation between apple associated rhizobacterial population and different plant growth promoting traits in (a) healthy and root rot infected apple orchards; (b) apple replant sites and new plantation apple orchards. Molecular diversity analysis employing techniques viz. amplified ribosomal DNA restriction analysis (ARDRA) and DNA sequence analysis of 16S rRNA gene revealed comparative insight into structural variations in rhizobacterial diversity. In planta evaluations using microbial formulations developed using PGPR strains viz. Bacillus licheniformis strain CKA1, B.methylotropicus strain CKAM, Serratia plymuthica strain G4(3), B.methylotropicus Strain RG1(3), and their consortium have been comprehensively evaluated in the present study. Bio-control potential of microbial formulations against phyto-pathogens has also been assessed using in planta experimentation. Strain CKA1 based bio-formulation proved to be the most effective as compared to all other PGPR strains in providing antagonism against pytopathogens as revealed by experimentations carried out under net house conditions. Attempts have also been made, in the present study to understand the genetic basis of mineral phosphate solubilization in strain CKA1. Cloning and sequencing of gdh gene has paved the way for understanding molecular mechanisms involved in nutrient mobilization of essential nutrient (phosphorus) and its subsequent enhanced uptake by plants, as mediated by the rhizobacteria. Multi-location trials were carried out with inoculation of B. licheniformis strain CKA1 to access its effect on early vegetative growth of apple plants under field conditions. Effect of strain CKA1 on vegetative growth of apple was also compared at fresh plantation and re-plantation sites. Results revealed significant increase in vegetative growth over un-inoculated controls at all the locations studied. Effect of liquid formulation of CKA1 on apple yield, pomological traits, and fruit content and nutrient parameters was also evaluated at different locations. Comparison of different application strategies of liquid formulation viz. soil drenching in basin of apple trees alone, foliar spray at pink bud stage and soil drenching in combination with foliar spray for three consecutive years revealed that maximum apple yield/tree (28.00kg at RHRS, Mashobra; 103.75kg at Sablog, Matiana; 20.23kg at Nanni, Matiana; 110.50kg at Kyari, Kotkhai) was observed when apple trees were treated with CKA1 using a combination of root inoculation and foliar spray. Population dynamics studies carried out to determine the fate of inoculated strain of CKA1 in apple rhizosphere revelled successful establishment and colonization of the inoculated strain as indicated by high values Simpson’s index of Dominance which ranged from 1.51 to 3.40 at different locations. Apple orchard rejuvenation projects are being ambitiously launched by State agencies for restoring six decade old planted apple orchards. Integrated nutrient management systems comprising biological systems especially, single strain multifunctional PGPR such as strain CKA1 opens up new avenues not only for improving crop yield but also in sustaining soil health.enApple (Malus domestica Borkh.),rhizobacteriaThesis