THE ROLE OF DRY LAND BACTERIA ISOLATES IN SUPPORTING ADAPTATION OF HOST PLANT TO DROUGHT STRESS

• Main Author: Fitriani Wangsa Putrie, Rahayu
• Format: Dissertations
• Language: Indonesia
• Subjects: Ilmu hayati ; Biologi
• Online Access: https://digilib.itb.ac.id/gdl/view/66009
• Institution: Institut Teknologi Bandung

The availability of agricultural land in Indonesia is dominated by dry land which area is predicted to increase due to global warming. Generally, plants do not grow well in those condition, but there is a phenomenon that certain plant species can grow well in extreme dry environments. This phenomenon is thought to be due to the influence of bacterial community factors which grow in plants. So far, there is no study related to the role of bacteria in overcoming drought stress, especially bacteria originating from 2 types of dry land climates in Indonesia (arid) and seasonally dry (drought). This study examines the role of bacteria originating from both type of dry climate in supporting the survival of host plants under drought stress conditions. These two types of land are thought to have unique bacterial diversity and can affect the drought tolerance of host plants. In general, this study aims to examine the effect of plant endophyte and rhizosphere bacteria from those types of dry land to increase the tolerance of model plants to drought with several specific objectives, namely: 1) Obtaining data on bacterial diversity in 2 types of dry land (arid and drought); 2) Obtaining potential bacterial isolates from 2 types of dry land (arid and drought) in supporting host plant survival against drought stress; 3) Determine the drought tolerance key factors of bacterial isolates in supporting their survival in drought stress; 4) Determine the effect of potential bacterial formulas in increasing the drought tolerance of model plants in greenhouse-scale. This research was divided into three research stages, namely: 1) Study of plant endophyte and rhizosphere bacterial diversity by metagenomic and isolation of potential 'culturable' bacteria from two type of dry land in Indonesia; 2) Selection of potential bacterial candidates based on their ability to produce key factors of drought tolerance via in vitro test which included survival at low osmotic potential (-0.73 MPa), ability to produce exopolysaccharides and growth hormones (IAA), high salinity and temperature resistance (40°C), low pH resistance (4), growth promoting effect and ability to produce ACC Deaminase and catalase enzymes; 3) In vivo evaluation on the role of potential bacterial formulas in supporting the survival of model plants under drought stress conditions. In the first phase of the research, the results of the metagenomic analysis showed that the two types of land have different patterns of bacterial diversity. In arid land, Proteobacteria, Actinobacteria, and Cyanobacteria were the most common genera, whereas in drought, Cyanobacteria, Proteobacteria and Gemmatimonadetes were the dominant genera. In total there were 308 culturable isolates were able to be isolated, 117 isolates from the arid land plant Kupang-Nusa Tegggara Timur and 191 isolates from the drought land plant Pangandaran-West Java and Pati-Central Java. In phase 2 research, 10 isolates were obtained, namely BAO 5, BDO 8, BTO 29, BTBO 4, BTBO 7, BAPG 9, BAPG 17, BAPG 19, BSPG 7, and BSPG 8 which were selected as candidate of formulas for dry land bioinoculants based on the highest value of key factors of drought tolerance. The candidates were selected to produce 3 inoculant formulas from arid land isolates and 2 inoculant formulas from drought land. In phase 3 research, the F2 formula showed the best ability to increase the tolerance of the model plant to drought stress via in vivo tests. The consortium formula consisted of BDO 8, BAO 5 and BTBO 4. Molecular identification based on the 16S rRNA gene sequence showed that these three isolates were identical as Bacillus cereus strain ATCC 14579T.112, Bacillus cereus strain WHX1 and Bacillus cereus ATCC 14579. The results of this study obtains new findings which can enrich the repertoire of knowledge and potential bacterial formulas that can be developed to a further stage for application to agricultural land in 2 types of dry land in Indonesia.