The role of biofertilizer “Mikrobat” as a stimulator to increase productivity and health of rice plants

Biofertilizer Mikrobat (Patent Certificate: No. IDP000059255 and Brand Certificate: No. IDM000613360) is a bacterial consortium containing four superior microbes, including Azotobacter sp. isolate AP08, Pseudomonas sp. isolate PP012, Lactobacillus sp. isolate LP032, and Streptomyces sp. isolate SP022 with their respective roles as nitrogen fixers, Phosphate and Potassium solvents, providers of auxin, cytokinins, vitamins, amino acids, and antibiotics. This biotechnological product can be used to loosen and nourish the soil, increase the activity of positive microorganisms in the ground, increase seed vigor, suppress plant pests and diseases, accelerate plant growth and improve production and yield quality. The results of trials on rice plantations in the Experimental farm of BPTPH Maros showed that the treatment of Mikrobat has the best results in suppressing bacterial leaf blight and blast diseases and increasing rice plant production. The intensity of BLB disease and blast on Brang Biji (hybrid variety) of 0% and 0.5% compared to controls 8% and 2%, respectively. The highest number of tillers reached 19.02 tiller than control with 13.98, while production achieved 12.74 tonnes/ha compared to the control 9.42 tonnes/ha.


Introduction
Rice is the primary commodity, a strategic staple food source for most of Indonesia's population and is consumed by around 90% of Indonesia's population.Rice consumption in Indonesia from January to December 2021 reached 30.03 million tonnes.The need for rice is expected to continue to increase in line with population growth.Indonesia's total rice production in 2021 is 54.42 million tons of dry milled grain (GKG), equivalent to 31.68 million tons of rice.This figure has decreased by 233.91 thousand tons or 0.43% compared to rice production in 2020, which reached 54.65 million tons of GKG, or the equivalent of 31.50 million tons of rice [1].The high demand for rice in Indonesia has encouraged efforts to increase national rice production by the government.
Efforts to increase rice productivity in Indonesia have encountered several obstacles, including attacks by pest.The cause of the disease is one of the pest, which is categorized as the main factor causing low rice productivity.The main diseases in rice that causes high yield loss is a blast and bacterial leaf blight (BLB) caused by Prycularia oryzae and Xanthomonas oryzae pv.oryzae (Xoo).Yield losses due to Xoo by 15-24% [2].
Therefore, appropriate efforts and strategies are needed to boost productivity and maintain the health of rice plants by using biological fertilizers.Biological fertilizers are beneficial bacterial 1230 (2023) 012074 IOP Publishing doi:10.1088/1755-1315/1230/1/012074 2 formulations consisting of microbes that can increase fertilizer efficiency, fertility, and soil health.Currently, there are many helpful plant bacterial formulation products available, including Mikrobat, which is a consortium formulation of four superior microbes that synergize with each other, namely Azotobacter sp., Pseudomonas sp., Lactobacillus sp., and Streptomyces sp., with their respective roles as nitrogen fixers, phosphorus solvent, provider of growth regulators, auxins, cytokinins, vitamins, and amino acids formulated in liquid form and produced through biotechnology processes to support the needs of organic agriculture.Several groups of microbes have been widely developed as biofertilizers in Indonesia, such as the nonsymbiotic nitrogen fixation bacteria (Azotobacter sp. and Azospirillum sp.), symbiotic nitrogen fixation bacteria (Rhizobium sp.), phosphate solubilizing bacteria (Bacillus sp. and Pseudomonas sp.), and decomposer bacteria (Lactobacillus sp. and Saccharomyces cerevisiae) [3]; [4]; [5].
Using biological fertilizers is expected to make plants grow healthier and free from significant diseases, meet nutrient needs, produce higher, sustainable yields, and reduce inorganic fertilizers.

Materials and methods
This research was conducted from January to June 2021 in the Experimental Field of the Food Crops and Horticulture Protection Agency, South Sulawesi Province, in Maros Regency.Treatments were arranged in a particular plot design with two factors, factor I was rice variety (V1 = Inpari 4 and V2 = Brang Biji), and factor II was biological fertilizer treatment (P1 = Mikrobat, P2 = Mikrobat + Paenybacillus polymyxa, P3 = Paenybacillus polymyxa, P4 = control).Thus obtained, as many as eight treatment combinations were used.Each treatment was repeated four times so that a total of 32 treatment plots were used.

Land preparation, seeds, and planting
The land is processed using a hand tractor then the ground is leveled.Every plot that has been leveled is left in a messy state.Seed preparation was carried out by soaking the rice seeds in each biological fertilizer treatment (1:50) for 12 hours.Seeds used as controls were soaked in sterile water for 12 hours.Furthermore, the treated rice seeds were sown in the nursery and re-applied with biological fertilizer (1:100) 5 days before removal.Planting is done after the seedlings are 14 days old after scattering.Spacing of 20 cm x 10 cm, in every two rows, a distance of 40 cm is given with a 2:1 legowo cropping system.

Treatment and applications of biofertilizer
Fertilizer application is carried out according to recommendations and fertilization recommendations from the technical team of the South Sulawesi Food Crops and Horticulture Service.Essential fertilization using urea and NPK fertilizer.Application of biological fertilizer treatment is carried out by spraying at the age of 15, 30, 45, and 60 HST according to the dosage on the instructions for using Mikrobat biological fertilizer.

Observation
Observations were made directly on rice plantations by calculating attack intensity, number of tillers, and production.Observations were made 10 times with an interval of once a week.

The number of tillers.
The number of tillers per clump was calculated from all the tillers formed until the generative phase.Area of symptoms on leaf surface > 75 > 100 %

Production (tonnes/Ha).
Production is calculated at harvest by weighing the dry harvested grain dry weight (GKP) by taking tiles, and the results are converted to Ha. Tile area 2.5 m x 2.5 m.

Number of tillers
The results of the research and analysis of variance showed that varieties, treatments, and interactions of varieties and treatments had a significant effect on the number of tillers.Based on the table above, the data on the number of tillers shows that the V2P2 treatment produced the highest number of tillers and was not significantly different from the V1P2, V2P1, and V2P3 treatments.The P2 treatment significantly increased the number of tillers per hill of Inpari 4 and Brang Biji varieties.These results indicate the application of consortium-based Mikrobat biofertilizers consisting of Azotobacter sp., Pseudomonas sp., Lactobacillus sp., Streptomyces sp., and P. polymyxa can increase the growth of rice plants.A previous study by [7] reported that Streptomyces was able to produce plant growth-promoting substances in the form of Indole Acetic Acid (IAA) and Gibberellic Acid (GA3).IAA is an endogenous auxin that stimulates germination, root length, cell division, and differentiation.Gibberellin affects germination, breaks seed dormancy, and promotes the transport of nutrients and minerals in the seed [8].

BLB and blast attack severity
The effect of biofertilizer treatment on the severity of BLB and Blast diseases in several rice varieties is presented in table 4. In the field experiment, the highest BLB disease severity (4%) was obtained from the V1P0 treatment, and the lowest disease severity (0%) was obtained from the V1P2 and V1P3 treatments on the Inpari 4 variety.The highest Blast disease severity (8.50%) was obtained from the V1P0 treatment, and the lowest disease severity was obtained from the V1P2, V1P3, V2P1, V2P2, and V2P3 treatments, with a value of 0%.Disease severity data show that all biofertilizer applications can improve plant health compared to controls.The most effective biological fertilizers in controlling BLB were V1P2 and V1P3, with 100% disease control efficacy, followed by V2P2 and V2P3, each with 87.5% disease control efficacy, and for Blast disease, the highest disease control efficacy was found in V1P2, V1P3, V2P1, and V2P2, with a value of 100%, followed by V1P1, with a disease control efficacy of 73.5%.
For BLB and Blast diseases, the biofertilizer formulation P2 showed the highest disease control for all rice varieties tested.This ability can be caused by P2 containing several microorganisms compared to P. polymixa.A microbial consortium (combination) is more effective than a single application in improving rice health by suppressing BLB and Blast diseases [9].The ability of a bacterium to fix nitrogen, dissolve phosphorus, produce siderophore compounds, nitrogen cyanide (HCN), chitinase enzymes, proteases, and cellulose is a desirable characteristic to obtain bacteria that have the potential to be evaluated in various characteristics.Azotobacter sp, besides its biological nitrogen fixation, also shows antagonism towards plant pathogenic fungi and bacteria [10].Mikrobat + P. polymixa is a bacterial formula that has the potential as a biological agent to control bacterial leaf blight and Blas disease.
[11] stated that P. polymyxa secretes an antibiotic compound in the form of polymyxin which has an inhibitory power against other microorganisms.Biofilms from P. polymyxa showed the production of exopolysaccharides in plant roots that could protect against pathogens.The test results in BB Biogen bacteria also contain the hormone gibberellins [12].The study [13] showed that P. polymixa isolates inhibited the growth of P. oryzae which causes blast disease in vitro testing.The longer the incubation period, the higher the pathogen inhibition index of P. oryzae.P. polymixa BRF-1 isolates from soybean rhizosphere produced antifungal peptides which functioned as antagonistic substances, dan P. polymixa JH2 produces an enzyme capable of degrading toxoflavin toxin [14].According to [15], the genus Pseudomonas sp.produces antibiotic compounds in the form of pyoluteorin and pyrrolnitrin, which are toxic to pathogens.Pseudomonas sp. can produce secondary metabolites, such as siderophores, that can suppress the growth of pathogenic bacteria by competing for Fe 2+ absorption and colonizing roots.[16] reported that actinomycetes strains, such as Streptomyces virginiae, could produce antimicrobial compounds and inhibit ten pathotypes of Xanthomonas oryzae pv.oryzae and not phytotoxic to rice.Therefore, biofertilizers based on the P2 consortium consisting of Azotobacter sp., Pseudomonas sp., Lactobacillus sp., Streptomyces sp., and P. polymyxa can work together to improve rice health and productivity.

Rice production
The effect of biological fertilizer treatment on rice production in several rice varieties is presented in table 5.The effect of applying biological fertilizers to several rice varieties is shown in table 5.The data showed that the highest yields were obtained from the biological fertilizer treatment P2, with an average value of 11.45 tons/ha, followed by P3, P1, and P0, with an average value of 11.13, 10.5, and 9.87 tons/ha respectively.All applications of biological fertilizers increase rice production yields, with the highest increase from the application of P2 biological fertilizers.The yield increase in the P2 treatment reached 33.7% compared to the control.This data is following table 4, where the V1P2 and V2P2 treatments showed the highest disease control efficacy compared to other treatments.These results prove that the application of consortium-based biofertilizers can increase rice productivity by improving soil fertility and health.
Currently, many products of beneficial plant bacterial formulations are available, including Microbat, a combination of biological ingredients, fertilizers, and microorganisms formulated in liquid form and produced through biotechnology processes to support the needs of organic farming.Microbes contain a variety of beneficial microorganisms that can increase crop production and are enriched with Streptomyces sp bacteria as biological controllers of plant diseases.[17] reported in their review that Azotobacter sp. has been widely used to fix N 2 associated with plant roots biologically, and [18] the use of Azotobacter as an N-biofertilizer increases the growth and yield of various crops in the field with percentage increases of up to 40% for Cauliflower and 15-20% for Maize compared to fertilizers conventional.

Conclusion
The combination treatment of Mikrobat + Paenybacillus polymyxa and Brang Biji variety showed the highest number of tillers, the lowest severity of blast disease and bacterial leaf blight and the highest rice plant production compared to the control treatment.

Table 1 .
[6].2.OPT attack rate.Observations aimed at the main diseases in rice cultivation, namely crackle, and blast, by calculating the severity of the disease with the formula: 1230 (2023) 012074 Blast disease severity scale system in rice plants[6]

Table 3 .
Maximum number of tillers of two rice varieties in biological fertilizer treatment Note: Numbers followed by the same letters (a,b,c) in the same column are not significantly different based on the LSD test at the α level of 0.05.

Table 4 .
The severity of BLB and blast diseases of two rice varieties on biofertilizer treatment

Table 5 .
Production of two varieties of rice on biological fertilizer treatment (tonnes/ha) Note: Numbers followed by the same letters (a,b,c) in the same column are not significantly different based on the LSD test at the α level of 0.05.