Ani Widiastuti

Effect of corn steep liquor on lettuce root rot (Fusarium oxysporum f.sp. lactucae) in hydroponic cultures

BACKGROUND Recent reports indicate that organic fertilisers have a suppressive effect on the pathogens of plants grown under hydroponic systems. Furthermore, microorganisms exhibiting antagonistic activity to diseases have been observed in organic hydroponic systems. This study evaluated the effect of corn steep liquor (CSL) on controlling lettuce root rot disease [Fusarium oxysporum f.sp. lactucae (FOL)] in a hydroponic system. The effect of CSL and Otsuka A (a chemical fertiliser) on the inhibition of FOL in terms of mycelial growth inhibition was tested in vivo. RESULTS Addition of CSL suppressed FOL infection rates. CSL inhibited FOL infection by 26.3-42.5% from 2 days after starting incubation. In comparison, Otsuka A inhibited FOL growth by 5.5-19.4%. In addition, four of 10 bacteria isolated from the nutrient media containing CSL exhibited inhibition zones preventing FOL mycelial growth. CONCLUSIONS We found that CSL suppressed FOL in lettuce via its antifungal and biostimulatory effects. We suggest that activation of beneficial microorganisms present in CSL may be used to decrease lettuce root rot disease and contribute to lettuce root growth.

Organic hydroponics induces systemic resistance against the air-borne pathogen, Botrytis cinerea (gray mould)

Here, we propose that organic hydroponics trigger induced systemic resistance (ISR) in lettuce against air-borne Botrytis cinerea, which causes gray mold. We compared effects of organic and chemical hydroponics, assessed presence of ISR elicitors in the hydroponic nutrient solution, and investigated molecular mechanism of ISR. Organic hydroponics significantly reduced gray mold lesions in lettuce (cultivated hydroponically) and cucumber (cultivated in soil and foliar sprayed with nutrient solution). The 1-aminocyclopropane-1-carboxylic acid synthase gene in lettuce and lipoxygenase and ethylene receptor-related gene in cucumber showed heightened expression, suggesting that the jasmonic acid/ethylene (JA/ET)-signaling pathway was involved in ISR for both crops. Low salicylic acid β-glucoside levels confirmed role of the ISR signaling pathway. ISR in both lettuce and cucumbers indicated that elicitors in organic hydroponics were nonhost-specific and that the JA/ET pathway was activated without microbe–root interaction. Thus, organic hydroponics can be an effective method for both soil-borne and air-borne disease control.

Genetic Diversity of Pyricularia oryzae, the Causal Agent of Rice Blast Disease, Based on Repetitive Element–Based Polymerase Chain Reaction

Pyricularia oryzae is a pathogen that causes rice blast disease. One of the challenges in controlling rice blast disease is the high diversity of P. oryzae. This study was conducted to analyze the genetic diversity of P. oryzae. Eleven samples were collected from the Special Region of Yogyakarta, nine samples from Central Java Province, and one sample from West Java Province, Indonesia. DNA samples of P. oryzae isolates were fingerprinted by using repetitive element–based polymerase chain reaction (rep-PCR) with two primers, Pot2–1 and Pot2–2. The results showed 25 amplified bands ranging in size from ±600 bp to ±3400 bp. A dendrogram showed that samples taken from nearby places did not always have high similarity. The dendrogram showed that all isolates were grouped in six clusters at a 70% similarity level. These results showed that the genetic diversity of P. oryzae is high and spread randomly.

Detection of Mycotoxin-Encoding Genes in Fusarium spp. Isolated from Maize Kernels in Indonesia

Fusarium spp. have a significant status as a plant pathogen in maize cultivation and post-harvest handling in Indonesia, for they not only devastate the crop in the field and during storage but also have potential capability to be a mycotoxin contaminant in maize-based food or feed. This research aimed to detect mycotoxin-encoding genes from 24 isolates of Fusarium spp. collected from maize kernels harvested in several maize cultivation center areas in Java and one isolate from Lombok Island, using specific primers. These Fusarium spp. had already been molecularly characterized and grouped as four species: F. verticillioides, F. graminearum, F. proliferatum, and F. asiaticum. The results showed that genes encoding fumonisin, deoxynivalenol, and zearalenone were detected in F. verticillioides, and genes encoding deoxynivalenol and zearalenone were detected in F. graminearum and F. asiaticum, while those mycotoxin-encoding genes were not detected in F. proliferatum on the basis of the specific primers used in this research. This is a principal study to considerably contribute further research in observing conditions that will be favorable for expression of those genes, in order to better manage maize post-harvest handling to avoid mycotoxin contamination.

Induction of Reactive Oxygen Species by Trichoderma spp. Against Downy Mildew in Maize

Downy mildew is the most important disease in maize and causes severe loss of maize productivity. Trichoderma spp., which can be used as biocontrol agents and plant inducers, could induce reactive oxygen species (ROS). This study aimed to know the potency of Trichoderma spp. in inducing downy mildew disease and inducing ROS. The production of ROS is one of the earliest cellular responses following successful pathogen recognition. There were four Trichoderma isolates in this study: JMA1, JMA2, KMA, and STA. The results showed that KMA, STA, JMA2, and JMA1 isolates significantly reduced disease intensity and the incidence of plant disease. Trichoderma spp. induced ROS as a response of plant resistance against downy mildew.

Induction of Resistance Using Trichoderma spp. and Penicillium sp. against Banded Leaf and Sheath Blight (BLSB) Caused by Rhizoctonia solani in Maize

Banded leaf and sheath blight (BLSB), caused by Rhizoctonia solani, is an important disease in maize. In this study, Trichoderma spp. and Penicillium sp. were used to control the disease. Experiments were conducted with five treatments: control (no treatment) (R0); R. solani inoculation (R1); Trichoderma spp. and R. solani inoculation (R2); Penicillium sp. and R. solani inoculation (R3); and combined Trichoderma spp., Penicillium sp., and R. solani inoculation (R4). The results showed that the heights of maize plants treated with R3, R2, or R4 did not differ significantly in comparison with R0 treatment but did differ significantly in comparison with R1 treatment. The numbers of leaves in maize plants treated with R4, R2, or R3 differed significantly in comparison with R0 and R1 treatment. The stem girths of maize plants treated with R2, R3, or R4 did not differ significantly in comparison with R0 treatment, but a significant difference was observed in comparison with R1 treatment. Peroxidase enzyme activity with R0, R2, R3, or R4 treatment was increased at 4 days and 8 days after inoculation; on the other hand, enzyme activity with R1 treatment was increased only at 4 days after inoculation and was then decreased at 8 days after inoculation. The intensity of disease ratings with treatments R0, R1, R2, R3, and R4 were about 2%, 28%, 10%, 9%, and 5%, respectively.