Yellow leaf curl disease of chili pepper caused by Pepper yellow leaf curl virus (PYLCV) has been reported as an important disease in Java and Bali. Disease severity reached 80−100% and it may cause significant yield losses. In order to reduce the negative impact of synthetic insecticides, silica application was evaluated for its potency to suppress the disease. A greenhouse experiment was conducted using randomly block design with 2 factors: PYLCV isolate (Java and Bali) and silica (SiO2) treatment (with and without). Parameters observed were disease symptoms, incubation period, disease incidence and severity, and total silica level. The symptoms of virus infection in Pelita 8 and Seret cultivars were yellow mosaic, leaf curl, green mosaic, dwarf, and cupping upward or downward. A Specific DNA fragment of 912 bp was successfully amplified from 4 samples. Four sequences were obtained and further analysis showed their highest homology, i.e. 96% and 97% with Pepper yellow leaf curl Indonesia virus-Java (PYLCIV-Java) (JX416180) and PYLCIV-KrthAl (LC381274), respectively. Infection by different virus isolates did not affect disease severity significantly. The application of silica was able to delay symptom development and to suppress the severity of the disease in the range of 16.67−30.33%. Silica application on the soil increased the total content of silica in the plants. However, a further experiment is required to understand the mode of action of silica in inducing plant resistance to the pathogen.

Abstract. Listihani L, Ariati PEP, Yuniti IGAD, Selangga DGW. 2022. The brown planthopper (Nilaparvata lugens) attack and its genetic diversity on rice in Bali, Indonesia. Biodiversitas 23: 4696-4704. The brown planthopper (Nilaparvata lugens) is an important pest on rice crops in Indonesia. The genetic diversity of BPH isolates in western Indonesia has been extensively reported, whereas eastern Indonesia isolates have not been reported. This research aims to analyze genetic diversity and evaluate the BPH attack's intensity on Bali rice plants. The research method used was an observation of attack percentage, population dynamics, attack intensity, and genetic diversity of BPH in 9 districts in Bali (Badung, Gianyar, Klungkung, Bangli, Karangasem, Tabanan, Denpasar City, Buleleng, and Jembrana). Molecular identification was carried out on N. lugens DNA in the mtCOI fragment. BPH attacks of >50% were found in the districts of Gianyar, Bangli, Jembrana, and Badung. The BPH population was primarily found in Ciherang and IR-64 varieties of rice in the Badung Regency, with 43.67 BPH per rice hill. In general, rice varieties grown in all observation locations were susceptible to BPH, such as Ciherang, IR-64, Inpari 32, and Situbagendit. In the Ciherang and IR-64 varieties, the highest attack intensity average value reached 30%. The sequence of N. lugens isolate from Bali Jembrana showed the highest nucleotide and amino acid homology with N. lugens isolate FSD-034 from Pakistan (MK301229) biotype Y of 99.5 -99.74% and 100%, respectively. This study found N. lugens biotype Y in rice plants for the first time in Indonesia. This study reported that Rice varieties Situbagendit and Inpari 32, previously resistant to BPH, are reported as susceptible to BPH.

Molecular identification of Pepper yellow leaf curl Indonesia virus on chili pepper in Nusa Penida Island. Pepper yellow leaf curl Indonesia virus (PYLCV) has been reported as caused yellow leaf curl disease in Bali Island since early 2012. Dominant symptoms of PYLCV infection in chili pepper were yellowing, leaf curl, yellow mosaic, and mottle. Bemisia tabaci, has been known to vector on the case yellow leaf curl disease. Observations on the Nusa Penida Island in 2020 showed symptoms such as yellow leaf curl disease, however, identification of PYLCV in Nusa Penida Island has not been studied. Molecular identification was conducted using polymerase chain reaction and sequence analysis. Data collected in this study was disease symptoms and disease incidence. The results showed that dominant disease symptoms caused by virus from Nusa Penida were yellow mosaic, yellowing, and mottle. Universal DNA fragments of 912 bp were successfully amplified from 50 leaf samples using Begomovirus degenerate primers SPG 1 (5’-CCCCKGTGCGWRAATCCAT-3’) and SPG 2 (5’ATCCVAA YWTYCAGGGAGCT-3’). Sequence analysis showed that the isolate from Nusa Penida was a Pepper yellow leaf curl Indonesia virus with a 98–100% homology with several reference isolates.

Yellow leaf curl disease in chili pepper has been reported in Bali Island since the early 2012. Research was conducted to identify the virus causing this disease and disease distribution in Bali. Field survey was carried out to observe disease intensity and to collect field samples from several chili pepper growing areas in Bali (Karangasem, Bangli, Tabanan, and Gianyar). Begomovirus identification from field samples was then conducted by polymerase chain reaction method using universal primers SPG1/SPG2, followed by an analysis of the amplified target DNA sequences. The incidence of pepper yellow leaf curl disease reached 100% at all sites and disease severity reached 18%−87%. Begomovirus specific DNA fragment measuring 912 bp was successfully amplified from 12 field samples. Sequence analysis of DNA fragments showed the highest homology with Pepper yellow leaf curl Indonesia virus (PYLCIV). Further phylogenetic analysis confirmed the relationship between PYLCIV isolates from Bali and various PYLCIV isolates from Indonesia.

A survey was conducted in several sweet potato cultivations in Bali Province. Survey found that many plants exhibited potyvirus symptom, such as chlorosis blotches. This study was to determine disease incidence, detection and identification of the virus causing these symptoms on sweet potato plants in Bali. Samples were collected by purposive sampling of 10 plants from each location in Bali (Denpasar, Gianyar, Badung, Buleleng, Tabanan, Klungkung, Karangasem, Jembrana, Bangli). Disease insidence was observed based on viral symptoms in the field. Identification of nucleic acids was done using Potyvirus universal primer and DNA sequencing. Disease incidence in Bangli, Buleleng, and Denpasar Regencies was > 50%. RT-PCR and CiFor/CiRev Potyvirus universal primers successfully amplified ± 700 bp of CI genes from all samples from Bangli, while samples from 8 other districts were not amplified using the same primers. The SPVC isolate of sweet potato showed nucleotide and amino acid homology similarities with the sweet potato isolate from East Timor (MF572066), 96.8% and 97.4%, respectively and these were referred to the "Asian" strain. This indicates that SPVC has spread in East Java and Bali.