RICE BACTERIAL BLIGHT

                                                           RICE BACTERIAL BLIGHT

Bacterial leaf blight (BLB) is caused by the bacterium Xanthomonas oryzae pv.oryzae. Pathogenic bacteria is commonly referred to as pathogens Xoo. In the general population of bacterial leaf blight disease is referred to as crackle. Maybe plants bacterial leaf blight disease crackle-crackle this sound when the wind, so as to facilitate eventual called crackle disease. Bacterial leaf blight disease attacks the rice plants from the nursery until the rice crop before harvest. The infection starts from the leaves through a wound like the cut rice seedlings or natural openings such as stomata of leaves (leaf holes) and damage the leaf chlorophyll, so that leaves the ability to perform photosynthesis was decreased and stunted plant growth. Bacterial leaf blight (BLB) is usually attacks the rice plant during the rainy season. Planting conditions with high humidity and unbalanced fertilization with high doses of nitrogen fertilizer. Planting Rice Varieties Resistant Bacterial leaf blight (BLB) Control of Bacterial leaf blight (BLB) by planting resistant varieties is done by planting rice varieties that are resistant to bacterial leaf blight disease is. At this time there have been several rice varieties that are resistant to multiple strains / pathotype bacterial leaf blight. The level of persistence against bacterial leaf blight varies between moderately resistant and resistant. Varieties - rice varieties are somewhat resistant to bacterial leaf blight disease, among others Ciliwung, Fatmawati, Mekongga and Aek Sibundoong (pathotype IV), Widas, Rokan and Hipa 3 (pathotype III and IV), Ketonggo, Ciherang, Inpari Inpari 2 and 3 (pathotype III), Tukad Unda and Tukad Petanu (pathotype VIII), Hipa 4, Hipa 5 Ceva, Hipa 6 Jete (pathotype IV and VIII), Inpari 1 and Inpari 6 Jete (pathotype III, IV and VIII). While the rice varieties resistant to bacterial leaf blight disease (HBD), among others Memberamo, Cibodas, Maros, Sintanur, Wera, (pathotype III), Way Apo Buru, Singkil, Konawe, Intani, Sunggal, Ketan Hitam (pathotype III and IV ), Code, Angke, Ciujung, Inpari 1, Inpari 6 Jete (pathotype III, IV and VIII). However, planting resistant varieties should also be done carefully. Strain / pathotype rapid bacterial leaf blight disease once formed strain / new, more virulent pathotype (virulent). So that the level of resistance of rice varieties resistant to bacterial leaf blight bacteria attack Xanthomoasn sp cause HDB also be not last long. In addition, resistant varieties are planted in a particular area can be susceptible varieties when grown in other regions, this was due to strain / pathotype HDB is rapidly shifting from one region to another region.

A.     Causes leaf blight disease

Leaf blight disease-causing bacterium Xanthomonas oryzae pv is oryzae. Scientific classification of bacteria is as follows.

Kingdom :  Procaryotae

Division  :  Gracilicutes

Class       :  Proteobacteria

Family    :  Psudomonadaceae

Genus     :  Xanthomonas

Species   :  Xanthomonas oryzae pv. oryzae

           Xanthomonas oryzae pv. oryzae (Xoo) is a Gram-negative bacterium that causes bacterial leaf blight (BLB) in rice. HDB classified as critical illness in many rice producing countries. This is because the HDB can reduce yields to varying degrees, depending on the stage of growth of the infected plants, the level of vulnerability of rice cultivars, and environmental conditions [1]. Losses incurred by the HDB in tropical areas is higher than in the subtropical region. HDB attacks in Indonesia cause yield losses of 21-36% in the rainy season and by 18-28% in the dry season [2]. HDB extensive disease transmission in 2006 reached more than 74 thousand ha, 16 ha of which cause plants puso [3]. Character tropical climate also means that many pathogenic strains were found in the tropics. In Indonesia, the emergence of the HDB was reported in 1950 and until now has found 12 Xoo strains with different levels of virulence. Strains IV and VIII are known to dominate the HDB attack on rice plants in Indonesia [4]. Diversity Xoo strain composition is also influenced by the growth stage of rice plants. Domination of the strain found in the seedling stage, flowering and ripening different [5]. The phenomenon of adult plant resistance, mutation, and natural heterogeneity character microorganism population is estimated as a factor affecting the composition of the strains with growth stage of rice plants.

B.      Leaf blight disease symptoms

Symptoms of bacterial leaf blight in rice plants are systematic and can infect plants at various stages of growth. Symptoms of the disease can be divided into three kinds, namely:

(1). Wilting symptoms (crackle) on young plants are sensitive or mature plants

(2). Symptoms of blight and

(3). Symptoms of a pale yellow leaves.

Wilting symptoms which became known as the crackle generally against the young plants aged 1-2 weeks after planting or crop vulnerable adults .At first symptoms are on the edge of the leaf or part of leaf wetness cuts a line spots, the spots are green extends keabu- gray, then the whole leaf becomes wrinkled and eventually wither like a scalded. Often when irrigation water is high, the plants wither and droop surface water menjadibusuk.Pada sensitive plants against this disease, the symptoms continued to grow until the entire surface of the leaf, sometimes rice sheath until mengering.Padapagi day humid weather, frequent bacterial exudate out to the leaf surface and easily fall by gusts of wind, wind friction, geekan leaves or rain splash. This exudate is an effective source of transmission. Bacterial leaf blight (BLB) is one of the diseases that can cause rice crops have puso. The disease is caused by the bacterium Xanthomonas oryzae pv. oryzae which can infect plants from seeding to harvest. There are two kinds of symptoms HDB. Symptoms appear at the time the plant was less than 30 days after planting, ie in the new plant nursery or moved to the field, called crackle. The symptoms at tillering to ripening called blight (blight). Specifically, the signs of the onset of infected plants are yellow to white spots, starting from the formation of aqueous bruising lines at the edges of the leaves. Spotting can start from one or both edges of the leaves are damaged and developed to cover the entire leaf blade. If the infection through the root or base of the stem, the plant looks dry as burnt.

C.      Identification Method Based and Molecular Physiology

Identification based on physiological character is first performed by Gram staining to see the types and forms of bacteria. Three isolates were allegedly Xoo is STG21, STG42, and STG46, further characterized physiologically by using a kit MicrogenTMGN-ID A + B panel. Isolates in the 24-hour media XA taken by 7 loops then dissolved in 10 mL of sterile 0.85% NaCl solution. A total of 20 mL in the pipette into each hole Microgen panel kit. Mineral oil is added to a particular panel hole and then incubated for 24 hours. After 24 hours, into the hole particular panel of reagents added as much as 20 mL. Reading of test results conducted by comparing the change in color of each test panel hole against color chart available. Other tests on the ability of starch hydrolysis, hydrolysis of casein, catalase, VP, and a fluorescent pigment test is done manually. Isolation of genomic DNA for molecular identification was conducted using CTAB (Cetyl Trimethyl Ammonium Bromide) [12]. Genomic DNA obtained was used to amplify the 16S rRNA gene. 16S rRNA gene was amplified using polymerase chain reaction machines (PCR) with specific primers for prokaryotes, ie 63F (5'-CAGGCCTAACACATGCAAGTC-3 ') and 1387r (5'-GGGCGGWGTGTACAAGGC-3') [13]. The composition of the PCR reaction consisted of Taq DNA polymerase enzyme La 0.25 mL, 12.5 mL 2X GC buffer, dNTP mixture 4 mL, 1 mL 63F primer, primer 1387r 1 mL, 2.25 mL ddH2O, and 4 mL of genomic DNA. PCR conditions used were predenaturasi (94 ° C, 5 min), denaturation (94 ° C, 1 min), annealing (55 ° C, 1 min), elongation (72 ° C, 1 min), and post-PCR (72 ° C, 7 min ) as many as 25 cycles. DNA separation of PCR products is done on a machine mini-gel electrophoresis using 1% agarose on the power supply voltage of 70 volts for 45 minutes. Visualization of DNA carried over UV dye Ethidium Bromide transluminator use (EtBr). DNA amplification product sequenced to determine the nucleotide base sequence using the services of PT Charoen Phokphand Indonesia, Jakarta. The nucleotide sequences of the results of the sequence and then aligned with the data GeneBank using BlastN program (basic local alignment search tool-nucleotides) from the NCBI website (National Center for Biotechnology Information).

D.     Leaf blight Disease Control Method

Control of bacterial leaf blight in rice plants in Indonesia have mainly relied on the use of pesticides, but due to the side effects of its use may be reduced, due to the residue left behind can be toxic and carcinogenic. Therefore, the development of biocontrol agents (biological agents) as a component of bacterial leaf blight disease control in an integrated rice-friendly environment needs to be developed and is expected to become an important alternative control in the era of sustainable agriculture. Biocontrol advantages, among others; safer, does not accumulate in the food chain, their reproduction process so as to reduce the use of repeated and can be used in conjunction with existing controls. Utilization of microorganisms as control agents seems still to be developed. Development of the use of such microorganisms should be based knowledge of the types of microorganisms, types of disease and also the mechanisms controlling plant diseases by using microorganisms. Utilization is expected to help control the disease without disturbing the environment There are a number of filosfer bacteria isolated from rice leaves as a potential biocontrol agent of bacterial leaf blight disease on a scale greenhouse. There filosfer bacterium Pseudomonas fluorescens and Bacillus sp groups were also isolated from the leaves and stems of rice plants as a potential biocontrol agent of late blight disease on rice in vitro. Bacterial leaf blight disease is effectively controlled with resistant varieties; complete fertilization; and water management. For areas that are endemic bacterial leaf blight disease, planting resistant varieties such as Code and Angke and use of NPK in the correct dosage. If possible, avoid continuous flooding, ie. 1 day 3 days flooded and drained (Suyamto, 2007).

Bacterial leaf blight disease intensity is not only influenced by the resistance of varieties and virulence of pathogens, but also influenced by farming techniques applied by farmers. As with other rice diseases, bacterial leaf blight disease has a clear relationship with fertilization, especially nitrogen fertilization. N fertilizer at the recommended dosage is important to increase vegetative growth and productivity. Instead of fertilizer N with high doses will increase the damage to the varieties with moderate resistance, although the impact of resistant varieties is relatively small. Therefore, excessive N fertilization should be avoided. In addition to fertilizer according to recommended dosage, varieties and crop rotation, sanitation and eradication in affected plants can be done to control the bacterial leaf blight disease in a particular area. Various varieties and rice lines with different levels of resistance to bacterial leaf blight has been developed. But then known resistant varieties is only effective against certain strains at a specific location. Research indicates that the pathogen Xanthomonas oryzae pv. Oryzae can form a new strain that is able to break the resistance of a variety. A few years after being released in 1970, reportedly susceptible to strain IR20 Isabela in the Philippines. While IR36 were released in 1979 reportedly susceptible to strain IV in 1982. This suggests that the resistance of rice varieties against bacterial leaf blight caused not only by the dominance and distribution of different strains in different regions, but also related to the period of the development of these varieties .

Period is determined by the resistance of a variety of factors, such as changes in strain rate, composition and dominance of strains, cultivation frequency, and the composition of varieties with different backgrounds gene planted in time and a certain expanse.

In addition, for the usual areas of interference from the disease danjurkan make efforts.

1. Stable. Planting resistant.

2. transplanted rice seedlings do not cut the tip of the leaves.

3. Move the seedlings at the age of not less than 40 days. For the species that are more susceptible age better plus.

4. For the species that are vulnerable are encouraged to plant 4-5 seeds per hill, with the  hope of one day no empty places.

5. Fertilization balanced.

6. Do not irrigate the nursery too deep.

7. If necessary, the disease can be prevented by soaking the seeds were cut leaves into  terusi solution of 0.05% for 30 minutes. Plants can be sprayed bactericidal fenazin-oxide 5 x 10 WP) at a dose of 0.1 kg / ha of active ingredient.