RESUMEN
Fusarium stem rot disease caused by Fusarium verticillioides has become one of the most serious issues confronting Indonesian farmers in recent years. An alternative option for suppressing this disease is to use indigenous microbes as an eco-friendly method to reduce synthetic fungicides. The objective of the research was to identify the molecular characteristics and effectiveness of an indigenous microbial consortium in controlling Fusarium stem rot disease. Identification of indigenous microbes is carried out based on molecular characters using universal primers, namely ITS-1/ITS-4 for fungi and 27F/1492R for bacteria. Nucleotide sequences were analyzed using Bioedit 7.2 version and MEGAX software. In vitro testing was carried out using the dual culture method for indigenous fungi and the disc diffusion method for indigenous bacteria. Meanwhile, in planta testing was conducted by evaluating a consortium of fungi and bacteria to control F. verticillioides in the field using a randomized block design with three replications, followed by a 5% DMRT test. The use of universal primer pairs ITS-1/ITS-4 and 27F/1492R succeeded in amplifying DNA bands of indigenous microbial isolates measuring ±600 bp and ±1465 bp, respectively. S6 and S9 bacterial isolates were identified as Bacillus cereus. JRP 7 and SEDF 6A isolates were identified as Trichoderma asperellum and JRP 10 isolate was identified as Penicillium raperi. All identification resulted in homology of >99%. The in vitro inhibitory reactions of isolates JRP 7, JRP 10, SEDF 6A, S6, and S9 against F. verticillioides were >60%. Disease severity of B6B9C10, B6B9C6, B6B9C7, B9C6C7, B9C7C10, and C6C7C10 treatments significantly proved their ability to control F. verticillioides in the field with a lower percentage of disease severity than positive controls, which are 23.33%, 18.89%, 23.33%., 21.85%, 14.07%, and 15.93%, respectively. The B9C7C10 consortium (S9 + JRP 7 + JRP 10 isolates) containing three species of indigenous microbes, i.e. B. cereus, T. asperellum, and P. raperi is the most effective at controlling F. verticillioides and may be developed for use as biopesticide products.
RESUMEN
The aim of this study was to evaluate the effectiveness of the combination of Bacillus subtilis TM3 formulation with botanical pesticides in suppressing Fusarium verticilloides infection in corn. The research was carried out at the Plant Pathology Laboratory and the Experimental Farm of Indonesian Cereals Research Institute (ICERI) from February to November 2019. The research consisted of two stages, namely an in vitro test of antagonists of botanical pesticides against F. verticilloides using 5 types of plant extracts namely betel leaf extract, turmeric, galangal, cosmos, and clove leaf. The second stage was to test the effectiveness of the combination of the formulation of B. subtilis TM3 with the best 3 types of plant extracts in vitro testing in suppressing F. verticilloides infection in plants. The results of the in vitro study showed that the plant extracts of betel leaf, clove leaf and galangal had the best inhibitory ability on the mycelia growth of F. verticilloides. Meanwhile, the field test found that the application of the B. subtilis TM3 formulation, either alone or in combination with plant extracts, was able to suppress F. verticilloides infection. The combination of B. subtilis TM3 formulation with betel leaf extract showed the best inhibition of 20% against stem rot disease and 13.33% against corn cob rot. This treatment did not affect production quantitatively, but was able to suppress the decline in seed quality due to F. verticilloides infection. Seeds grown by the Plastic Rolled Paper Test (PRPT) method were not only infected with F. verticilloides, but also infected with other seed-borne pathogens, such as Aspergillus niger and A. falvus. The presence of these two pathogens did not inhibit the growth of F. verticilloides in kernels.
RESUMEN
Indigenous fungi can suppress infection by pathogens and produce secondary metabolites that directly or indirectly affect plant growth. This study aimed to test indigenous fungi collected from corn plants as biological control agents and their effects on the viability and vigor of corn seeds. Purposive sampling method was used for sampling where soil samples taken from the rhizosphere zone, corn stem and leaf tissue from three locations namely Maros-South Sulawesi, Bone-South Sulawesi, Sigi-Central Sulawesi, Indonesia. Rhizospheric fungi were isolated from soil collected at the rhizosphere and rhizoplane using a serial dilution technique, while the endophytic fungi isolated from the leaves and stem tissues using surface sterilization method. The isolated fungi were cultured on a potato dextrose agar (PDA) medium. An antagonism test was performed using the dual culture method on PDA media with F. verticillioides as target pathogen. Pathogenicity test and the effect of fungi on corn seed germination was carried out using the blotter test method. Parameters observed were; necrotic symptoms on seedlings, growth potential, germination, growth rate, growth simultaneity, vigor index, germination rate, and time needed for 50% of the total germination. The effect of the isolated indigenous fungi on corn growth was carried out in-planta using seedling trays. The results of the blotter test and in-planta test were further confirmed by a physiological characteristic test. And assessing the fungi's ability to dissolve potassium, phosphate, and produce protease enzymes. A total of 89 fungal isolates were isolated and collected from various parts of the corn plant. Nineteen of the 89 fungal isolates showed inhibitory activity against F. verticillioides by ≥ 50% inhibition. The fungal isolates JRP 5 MRS, JRP 9 MRS, JRP 10 MRS, JRP 7 MRS, and JEDF 1B BN were selected based on the tests and showed a consistently positive effect on seed viability and vigor with a value of ≥90%. The isolates did not cause necrosis in corn, and had the ability to suppress the growth of pathogenic F. verticillioides by ≥ 50%.