PENYAKIT TUNGRO PADA TANAMAN PADI (Oryza sativa) DI KECAMATAN TABA PENANJUNG : INSIDENSI PENYAKIT DAN DETEKSI VIRUS SECARA MOLEKULER

[TUNGRO DISEASE ON RICE PLANT (Oryza sativa) IN TABA PENANJUNG DISTRICT: DISEASE INCIDENCE AND MOLECULAR DETECTION OF VIRUSES]. Tungro is one of the important diseases of rice plants. Tungro disease caused by Rice tungro bacilliform virus (RTBV) and Rice tungro spherical virus (RTSV). This research aims to obtain information on the spread of the disease, vector population, and molecular detection by polymerase chain reaction method. This research was conducted from December 2019 to April 2020 in rice fields in Taba Penanjung sub-district, Bengkulu Tengah district at ± 540 meters above sea level and virus detection in the Laboratory of Biotechnology and Genetics Department of Biology Faculty of Mathematics and Natural Sciences (MIPA) and Laboratory of Plant Protection, Agriculture Faculty, Bengkulu University. Data analysis used descriptive analysis. The results showed that the highest disease incidence on the seven weeks after planting (wap) is 1.7% and the highest population of the vector on the 7 wap with an average of 7.7 vector/100m2 in the village of Taba Penanjung. Detection of viruses with the PCR method with the specific primer DAF/DAR succeeded in amplification of DNA band measuring 1,400 bp. RTSV was not detected by RT- PCR using a specific primer or RTSV. The result of this detection shows that the symptoms of tungro on rice plants in the cultivation of Taba Penanjung district associated with RTBV infection. RTSV unable to detect can be caused by many factors in the detection process, including total RNA extraction, cDNA synthesis, DNA amplification, and DNA visualization of PCR products.

Coordinated action of RTBV and RTSV proteins suppress host RNA silencing machinery

RNA silencing is as an adaptive immune response in plants that limits accumulation or spread of invading viruses. Successful virus infection entails countering the RNA silencing for efficient replication and systemic spread in the host. The viruses encode proteins having the ability to suppress or block the host silencing mechanism, resulting in severe pathogenic symptoms and diseases. Tungro virus disease caused by a complex of two viruses provides an excellent system to understand these host and virus interactions during infection. It is known that Rice tungro bacilliform virus (RTBV) is the major determinant of the disease while Rice tungro spherical virus (RTSV) accentuates the symptoms. This study brings to focus the important role of RTBV ORF-IV in Tungro disease manifestation, by acting as both the victim and silencer of the RNA silencing pathway. The ORF-IV is a weak suppressor of the S-PTGS or pre-established stable silencing but its suppression activity is augmented in the presence of RTSV proteins. The RTBV and RTSV proteins interact to suppress localized silencing as well as spread of silencing, in the host plants.

PREFERENCE TEST OF GREEN LEAFHOPPER (Nephotettix virescens Distant) TO SOME TUNGRO-RESISTANT PROMISING LINES

Preference test of green leafhopper (GLH) Nephotettix virescens Distant to some tungro-resistant promising lines. Tungro is the most important diseases of the rice plant, caused by two types of viruses, namely Rice Tungro Bacilliform Virus (RTBV) and Rice Tungro Spherical Virus (RTSV), transmitted by green leafhopper (GLH) especially Nephotettix virescens Distant in a semi- persistent manner. The aim of this research was to study some of the varieties dislike (resistant) to GLH and resistant to rice tungro virus. The study was conducted on Januari to August 2019 at Green House of Indonesian Tungro Disease Research Station and at farmer’s field in Polman West Sulawesi. The experiment in the green house was preference and survival test using a Randomized Completely Block Design (RCBD) with three replications. The materials consisted of 48 tungro-resistant promising lines and 2 varieties as a check. The field experiment using an augmented design with four blocks. Every block consisted of 20 promising lines and four varieties of checks (Ciherang, Tukad Unda, Inpari 9 Elo, and IR 64). Variables observed were the number of GLH present and survival in promising lines, the population of GLH at the field, the percentage of tungro incidence, the filled with spikelet number, the unfilled of spikelet number, the weight of 1000 grain, and the grain yield at 14% moisture content. The results showed that ten promising lines was dislike (resistant) to GLH and resistant to rice tungro virus with the percentage of tungro incidence lower or equal than resistant check varieties (Inpari 9) and had high yield potential (6,2 – 10,2 t/ha).

Engineering Plant Resistance to Tomato Yellow Leaf Curl Thailand Virus Using a Phloem-Specific Promoter Expressing Hairpin RNA

Transgenic approaches employing RNA interference (RNAi) strategies have been successfully applied to generate desired traits in plants; however, variations between RNAi transgenic siblings and the ability to quickly apply RNAi resistance to diverse cultivars remain challenging. In this study, we assessed the promoter activity of a cauliflower mosaic virus 35S promoter (35S) and a phloem-specific promoter derived from rice tungro bacilliform virus (RTBV) and their efficacy to drive RNAi against the endogenous glutamate-1-semialdehyde aminotransferase gene (GSA) that acts as a RNAi marker, through chlorophyll synthesis inhibition, and against tomato yellow leaf curl Thailand virus (TYLCTHV), a begomovirus (family Geminiviridae) reported to be the prevalent cause of tomato yellow leaf curl disease (TYLCD) in Taiwan. Transgenic Nicotiana benthamiana expressing hairpin RNA of GSA driven by either the 35S or RTBV promoter revealed that RTBV::hpGSA induced stronger silencing along the vein and more uniformed silencing phenotype among its siblings than 35S::hpGSA. Analysis of transgenic N. benthamiana, 35S::hpTYLCTHV, and RTBV::hpTYLCTHV revealed that, although 35S::hpTYLCTHV generated a higher abundance of small RNA than RTBV::hpTYLCTHV, RTBV::hpTYLCTHV transgenic plants conferred better TYLCTHV resistance than 35S::hpTYLCTHV. Grafting of wild-type (WT) scions to TYLCTHV RNAi rootstocks allowed transferable TYLCTHV resistance to the scion. A TYLCTHV-inoculation assay showed that noninfected WT scions were only observed when grafted to RTBV::hpTYLCTHV rootstocks but not 35S::hpTYLCTHV nor WT rootstocks. Together, our findings demonstrate an approach that may be widely applied to efficiently confer TYLCD resistance.

PENGARUH APLIKASI PUPUK SILIKA DALAM PENGENDALIAN TUNGRO

Tungro adalah salah satu penyakit penting pada padi, yang disebabkan oleh dua jenis virus, yaitu Rice Tungro Bacilliform Virus (RTBV) dan Rice Tungro Spherical Virus (RTSV), melalui vektor wereng hijau (Nephotetic virescens). Tingginya intensitas pertanaman menyebabkan keseimbangan unsur hara semakin berkurang, termasuk unsur silika (Si). Pemberian pupuk silika dengan dosis yang tepat dapat meningkatkan kesuburan tanah dan menyebabkan tanaman lebih tahan terhadap serangan hama penyakit. Tujuan penelitian ini untuk mengkaji pengaruh pemberian pupuk silika dalam pengendalian penyakit tungro. Penelitian menggunakan rancangan faktorial dua faktor. faktor pertama yaitu dosis pemberian pupuk silika (kontrol, NPK dosis umum digunakan petani, 1/3 NPK + 1 lt si, 1/3 NPK + 3 lt si, 1/3 NPK + 5 lt si), faktor kedua adalah penggunaaan varietas (inpari 36 dan TN1). Hasil penelitian menunjukkan bahwa interaksi pemberian dosis pupuk silika dan varietas tidak berpengaruh nyata terhadap semua parameter pengamatan, kecuali pada hasil gabah. Varietas berpengaruh nyata terhadap tinggi tanaman, panjang malai, dan hasil gabah.

Complete Genome Sequence of Rice Tungro Bacilliform Virus Infecting Asian Rice (Oryza sativa) in Malaysia

Rice tungro disease was discovered in Malaysia in the 1930s. The first and only genome of Rice tungro bacilliform virus (RTBV) isolated from rice in Malaysia was sequenced in 1999.