Abstract. Mustaka Z, Patandjengi B, Alam G, Melina. 2022. Potential of rhizobacterial consortium in increasing area and weight of mulberry leaves (Morus indica). Biodiversitas 23: 1369-1374. Rhizobacteria are a group of bacteria that live saprophytically in the rhizosphere area. Some of them can act as plant growth promoters and as biocontrol agents against diseases to increase crop yields. This study was conducted to find potential of the rhizobacteria consortium in various treatments to increase the area and weight of mulberry (Morus indica L.) leaves. Results showed that the rhizobacteria consortium formulation had a significant effect on increasing leaf area and weight. The percentage increase in leaf area in the treatment using the MKR15 rhizobacteria consortium was better at 39.28% (2,800 mm2) when compared to the control MK0t (1,700 mm2), and the percentage increase in MKR15 leaf weight (74.80 g) was 54.54% higher compared to control MK0t (34 g). With these results, it is clear that the rhizobacteria consortium as PGPR affects plant growth and nutrition in a very specific way involving bacterial components that induce plant responses. Molecules of PGPR can affect plants in complex mechanisms, sometimes affecting plant growth and nutrition, and resistance simultaneously.

Abstract. Suriani, Patandjengi B, Muis A, Junaid M, Mirsam H, Azrai M, Efendi R, Sebayang A. 2023. New corn resistant lines to stalk rot disease (Dickeya zeae) in Indonesia. Biodiveritas 24: 3190-3200. Stalk rot disease caused by Dickeya zeae is one of the important diseases of corn in Indonesia. Host resistance cultivars are an effective and sustainable control measure of the disease. Therefore, the present study aimed to evaluate the resistance of 15 S1 hybrid maize lines to stalk rot disease. The research was conducted in two seasons (DS and WS) using a randomized block design with 3 replications. The D. zeae suspension with 108cfu/mL concentration was inoculated into the plant test 45 Days After Planting (DAP). Disease incidence and severity were observed during the two seasons. The results showed that all tested lines were infected with stalk rot disease but had various resistance reactions. Disease incidence and severity in the dry season were higher than in the rainy season. In the rainy season all test lines followed the 3 models of disease development, but in the dry season, all lines followed the monomolecular model. Further analysis showed that 3 lines of hybrid maize had the lowest AUDPC value with a protection index of more than 50% in two growing seasons. Stalk lignin content had negative correlation with a disease incidence of -0.60877, so it can be used as a parameter of plant resistance to disease. Tested lines that show resistance to the disease could potentially be useful as new varieties of maize.

Abstract. Suriani, Patandjengi B, Muis A, Junaid M, Mirsam H, Azrai M. 2023. Morpho-physiological and molecular characteristics of bacteria causing stalk rot disease on corn in Gorontalo, Indonesia. Biodiversitas 24: 1749-1758. Stalk rot disease was observed in corn in Gorontalo with typical symptoms, such as soft rot on the stalk, leaf wilting, and plant death. This study aimed to characterize the bacteria causing stalk rot disease in corn. Samples of infected plants were collected and identified morphologically, physiologically, and molecularly. The results showed that nine bacterial isolates were isolated from infected plants. All nine isolates showed positive hypersensitive responses on tobacco leaves. In comparison, only two bacterial isolates (BGO1 and BGO4) were positive on pathogenicity tests on corn. However, the BGO4 isolate caused the highest disease incidence with a faster incubation period. The BGO4 isolate was gram-negative with white-gray colored colonies. Physiological characterization of BGO4 also showed: positive catalase and indole, oxidase negative, fermentative oxidation, caused soft rot on potato, non-fluorescent, and sensitive to erythromycin. In addition, it can grow at 37-40°C and 5% NaCl, producing protease and lecithinase enzymes. The BGO4 also isolates infected rice, corn, sorghum, foxtail millet, celery, and Aloe vera. Morpho-physiology characteristics and diagnostic amplification of DNA by PCR using the Dickeya-specific primers (ADE1/ADE2) showed that the isolate belongs to the genus Dickeya. Further molecular characterization by analysis of the 16S rDNA using universal primer 27F/1497R successfully amplified the DNA band of BGO4 isolate measuring ±1300 bp. Phylogenetic analysis showed that it was in the same group as Dickeya zeae strain MS32 from Taiwan, strain DZ15SB01 (Thailand), and strain HNJF02 (China), with the coefficient of genetic distance ranging from 0.001 to 0.002. This study is the first report of D. zeae infecting corn in Gorontalo.