Salinity is one of the most damaging abiotic stresses due to climate change impacts that affect the growth and yield of crops, especially in lowland rice fields and coastal areas. This research aimed to isolate potential halotolerant plant growth-promoting rhizobacteria from different rhizo-microbiome and use them as effective bioinoculants to improve rice growth under salinity stress conditions. Bioassay using rice seedlings was performed in a randomized block design consisting of 16 treatments (control and 15 bacterial isolates) with three replications. Results revealed that isolates S3, S5, and S6 gave higher shoot height, root length, and plant dry weight compared with control (without isolates). Based on molecular characteristics, isolates S3 and S5 were identified as Pseudomonas stutzeri and Klebsiella pneumonia. These isolates were able to promote rice growth under salinity stress conditions as halotolerant plant growth-promoting rhizobacteria. These three potent isolates were found to produce indole-3-acetic acid and nitrogenase.
Agriculture is the best foundation for human livelihoods, and, in this respect, crop production has been forced to adopt sustainable farming practices. However, soil salinity severely affects crop growth, the degradation of soil quality, and fertility in many countries of the world. This results in the loss of profitability, the growth of agricultural yields, and the step-by-step decline of the soil nutrient content. Thus, researchers have focused on searching for halotolerant and plant growth-promoting bacteria (PGPB) to increase soil fertility and productivity. The beneficial bacteria are frequently connected with the plant rhizosphere and can alleviate plant growth under salinity stress through direct or indirect mechanisms. In this context, PGPB have attained a unique position. The responses include an increased rate of photosynthesis, high production of antioxidants, osmolyte accumulation, decreased Na+ ions, maintenance of the water balance, a high germination rate, and well-developed root and shoot elongation under salt-stress conditions. Therefore, the use of PGPB as bioformulations under salinity stress has been an emerging research avenue for the last few years, and applications of biopesticides and biofertilizers are being considered as alternative tools for sustainable agriculture, as they are ecofriendly and minimize all kinds of stresses. Halotolerant PGPB possess greater potential for use in salinity-affected soil as sustainable bioinoculants and for the bioremediation of salt-affected soil.
Weed competition will reduce rice yield. The research aimed to study the effect of difference weed control methods on rice yield in SOBARI. It has been conducted from October 2013 until February 2014, using Randomized Block design with five treatments (A = manual weeding, B = unweed control, C = herbicide containing Penoxulam + Cyhalofop-butyl, D = Bispyribac sodium, and E = 2, 4 D + Methyl metsulfuron). The results showed that weed control using herbicides containing Bispyribac sodium and 2.4 D + Methyl metsulfuron showed similar results as manual weed control on rice yield.
The diazotroph bacteria as ecofriendly biofertilizers play an important role in improving the N status and availability of paddy soil. Laboratory experiment to study nitrogenase activity and IAA production of diazotroph from rice rhizosphere and to assess its effect on the growth of rice seedling has been conducted from September to October 2014 in Agronomy and Horticulture Laboratory Faculty of Agriculture Jenderal Soedirman University, Purwokerto. The experiment was arranged as a completely randomized design and consisted of seven treatments and provided with 4 replications. The treatments were the isolates of indegenous diazotroph (T1 = A11003, T2 = A230041, T3 = A24001, T4 = A230022, T5 = A230021, T6 = A230042 and T7 = without inoculation). The nitrogenase activity measured by acetylene reduction assay method and IAA production was measured by HPLC method. Plant height, leaf greeness, leaf area, total dry weight and total root length were determined on 21 days after sowing. The experimental results showed that the isolat A230021 was identified as Rhizobium sp. LM-5 and have the highest nitrogenase activity at 0.07 µM C2H4 ml -1 h -1 and IAA production reached 19.01 ppm. Inoculation with strains of diazotroph enhanced chlorophyl content, total root length, and biomass production.
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