Rizobakteria Bacillus sp. dan Pseudomonas sp. Pemacu tumbuh toleran kekeringan dan aplikasinya pada tanaman jagung

Abstract

Agricultural land in Indonesia was largely dominated by untapped dry land. Maize (Zea mays L.) is one of the staple crops that are known could be cultivated on dry land. The future of agricultural development strategy oriented to the application of biological fertilizers and optimize ecological function of each ecosystem component. Rhizosphere has been known to contain microorganisms that can improve the plant growth, both directly and indirectly. Those rhizobacteria was known as plant growth promoting rhizobacteria (PGPR), include genus of Bacillus and Pseudomonas. Rhizobacteria had adapted to drought conditions, one way by producing exopolysaccharide (EPS). Therefore, this research was aimed to screening of rhizobacteria of Bacillus and Pseudomonas drought tolerant as growth promoter of maize growth. Utilized of rhizobacteria could be alternative way that are effective and environmental friendly. Screening in vitro of rhizobacteria as growth promoter of 47 Bacillus CR and 34 Pseudomonas CRB resulted 24 and 9 isolates were able to stimulate the growth of maize sprouts, significantly. Further screening of those growth promoter of the rhizobacterial isolates to drought tolerance with PEG 6000 resulted 7 isolates of Bacillus CR and 6 isolates of Pseudomonas CRB that were able to grow on medium with osmotic pressure -1 MPa and -2 MPa, respectively. Rhizobacterial isolates of growth promoter and drought tolerance were tested for antagonist mechanisms which aims to determine ability to live together in one medium if to be made formulation. Both non antagonist rhizobacterial isolates were evaluated for their potential in producing EPS by Dubois method. CRB 19 and CR 90 exhibited the highest activity of EPS production up to 0.346 mg mL-1 on medium with -2.0 MPa and 0.107 mg mL-1 on medium with -0.73 MPa, respectively. Based on 16S rRNA sequence analysis revealed that CRB 19 and CR 90 belonged to Pseudomonas aeruginosa strain B2 and Brevibacillus brevis B33, respectively. Four of potential isolates of each genus to be made formulation using peat soil as carrier material (F1, F2, F3 and F4). In addition, CRB 19 and CR 90 as selected isolates of each genus also to be formulated. Formulation were selected based on the highest of OD and EPS value. Rhizobacterial formula were further applied in planta in greenhouse using a completely randomized design with two factors (water content and formula). Water content consists of two levels (field capacity and under of field capacity), and the formula consists of seven levels (six formulas+control). In planta test showed that formula CRB 19 and F3 (CR 83+CRB 10) were the best formula that could enhance plant growth parameters compared to other formula. Furthermore, those drought tolerant rhizobacteria had potency to be developed as inoculants of maize planted in dry land agriculture.