Bacterial Leaf Blight Disease Research Articles

PERTUMBUHAN, HASIL DAN TOLERANSI GENOTIP PADI TERHADAP PENYAKIT HAWAR DAUN (Bacterial Leaf Blight) PADA APLIKASI DOSIS Paenibacillus Polymixa BERBEDA

The research was to study the effect of genotype rice plants and Paenibacillus Polymixa dose to growth, yields and genotype tolerances to BLB (Bacterial Leaf Blight) deseases.The research was conducted in the village Kedawung Majalaya Karawang District of West Java in the rainy season, from Januari 2015 until Mei 2015. The experiment was used Strip plots design with genotypes of rice was the main plot consist of Sri Putih (v1), Manohara (v2) and IR 64 (v3), subplots were doses paenybacilus polymixa (d1 ) Dose Paenybacillus polymixa 0 liters / ha, (d2) Dose Paenybacillus polymixa 2.5 liters / ha (5 ml / liter), (d3) Dose Paenybacillus polymixa 5 liters / ha (10 ml / liter) and (d4) Dose Paenybacillus pol ymixa 7.5 liters / ha (15 ml / liter). The results of the experiment shosed that no interaction between the administration of the dose variation Paenybacillus polymixa with genotype rice plants against rice yields and not interaction between administration of the dose variation Paenybacillus polymixa with genotype rice plants to suppress the intensity of the attack Bacterial leaf blight disease. For the intensity of the disease, dose applications Paenybacillus polymixa 2.5 liters / ha (5 ml / liter) was effectively used during the vegetative age of 21, 28 and 35 days after planting.

Leaf Blight Disease caused by <i>Pseudomonas syringae</i> pv. <i>syringae</i> in the Nurseries of Litchi (<i>Litchi chinensis</i> Sonn.) and its Management

Leaf blight of seven varieties of litchi caused by Pseudomonas syringae pv. syringae was surveyed in the nurseries of major litchi growing areas in Bangladesh viz. Rajshahi, Dinajpur, Rangpur, Mymensingh and Khagrachari. The mean level of incidence and severity were 8.58 and 7.88% in Rajshahi, 9.88 and 8.88% in Dinajpur, 8.44 and 7.76% in Rangpur, 6.50 and 6.18% in Mymensingh and 9.00 and 7.98% in Khagrachari. Incidence and severity of bacterial leaf blight disease of litchi varied significantly depending on weather conditions. Correlation studies revealed that bacterial leaf blight disease of litchi seedlings were positively correlated with temperature, rainfall and relative humidity, where temperature and rainfall was the major factor to the variations of both incidence and severity. Antibiotic sensitivity test revealed that among fifteen isolates, most of the isolates of P. syringae pv. syringae collected from litchi were sensitive to Gentamycin and Erythromycin. Under net house condition, six different treatments (i) Gentamycin @ 0.05%, (ii) Erythromycin @ 0.05%, (iii) Doxycycline @ 0.05%,(iv) Copper sulphate @ 0.05%, (v) BAU-Biofungicide @ 2% and (vi) Control were used for controlling bacterial leaf blight of litchi (Variety: China-3). BAU-Biofungicide was found to be superior in controlling bacterial leaf blight of litchi that reduced 33.64% disease incidence and 60.77 % disease severity in 2010-11 and 63.76% disease incidence and 61.40 % disease severity in 2011-12 over control when applied as foliar spray @ 2% followed by Copper sulphate (0.05%) and Erythromycin (0.05%).The Agriculturists 2017; 15(1) 10-18

Potensi Pseudomonas sp. untuk Mengendalikan Penyakit Hawar Daun Bakteri (Xanthomonas oryzae pv. Oryzae) Secara In Vitro

Tujuan penelitian ini untuk mengetahui potensi Pseudomonas sp. asal rhizosper padi sebagai agen hayati untuk mengendalikan penyakit hawar daun bakteri (Xanthomonas oryzae pv. oryzae) secara in vitro. Penelitian dilaksanakan di Laboratorium Agroekoteknologi, Fakultas Pertanian, Universitas Sultan Ageng Tirtayasa pada bulan Juni-September 2014. Penelitian menggunakan rancangan acak lengkap non faktorial dengan lima ulangan. Perlakuan terdiri dari 6 isolat Pseudomonas sp. (Ps 6, Ps 29, Ps 39, Ps 40, Ps 45, dan Ps 46) yang memiliki kemampuan antagonis dan 1 kontrol air (tanpa bakteri) sebagai pembanding, sehingga terdapat 35 satuan percobaan. Isolat-isolat bakteri Pseudomonas sp. yang diuji daya hambatnya secara analisis tidak memiliki pengaruh, baik antar isolat maupun terhadap kontrol (tanpa bakteri perlakuan). Namun, secara keseluruhan mempengaruhi yaitu dengan terbentuknya zona bening menunjukkan adanya tingkat pengendalian. Isolat-isolat bakteri Pseudomonas sp. memiliki kemampuan yang relatif sama dalam mengendalikan bakteri Xanthomonas oryzae pv. oryzae. Meski demikian, isolat Ps 39 dan memiliki zona bening yang cenderung lebih tinggi.

Stability of Four New Sources of Bacterial Leaf Blight Resistance in Thailand Obtained from Indigenous Rice Varieties

Bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most serious diseases in rice production. Breeding varieties specifically for their resistance to BLB disease is therefore an efficient and cost-effective strategy. However, the resistance gene for BLB can be race and non-race specific, meaning it is often overcome by the pathogen. The identification of new sources of resistance genes for Xoo is crucial in rice breeding programmes. In this study, six rice varieties were assessed using six Xoo isolates in multiple screening conditions. The GGE biplot analysis considers both genotype (G) and genotype environment (GE) interaction effects and demonstrates GE interaction. The first two principal components (PCs) accounted for 95.46% of the total GE variation in the data. Based on lesion length and stability performance, Phaladum was the most ideal genotype against all Xoo isolates in the four screening conditions. The results relayed that Phaladum indigenous rice varieties could be considered as new sources of bacterial leaf blight resistance in Thailand. In the future, the BLB resistance gene in this variety will be identified in regard to mode of inheritance and used as parental line in rice breeding programmes for resistance to BLB.

Phenotyping of VIGS-mediated gene silencing in rice using a vector derived from a DNA virus.

Target genes in rice can be optimally silenced if inserted in antisense or hairpin orientation in the RTBV-derived VIGS vector and plants grown at 28°C and 80% humidity after inoculation. Virus induced gene silencing (VIGS) is a method used to transiently silence genes in dicot as well as monocot plants. For the important monocot species rice, the Rice tungro bacilliform virus (RTBV)-derived VIGS system (RTBV-VIGS), which uses agroinoculation to initiate silencing, has not been standardized for optimal use. Here, using RTBV-VIGS, three sets of conditions were tested to achieve optimal silencing of the rice marker gene phytoene desaturase (pds). The effect of orientation of the insert in the RTBV-VIGS plasmid (sense, antisense and hairpin) on the silencing of the target gene was then evaluated using rice magnesium chelatase subunit H (chlH). Finally, the rice Xa21 gene, conferring resistance against bacterial leaf blight disease (BLB) was silenced using RTBV-VIGS system. In each case, real-time PCR-based assessment indicated approximately 40-80% fall in the accumulation levels of the transcripts of pds, chlH and Xa21. In the case of pds, the appearance of white streaks in the emerging leaves, and for chlH, chlorophyll levels and F v/F m ratio were assessed as phenotypes for silencing. For Xa21, the resistance levels to BLB were assessed by measuring the lesion length and the percent diseased areas of leaves, following challenge inoculation with Xanthomonas oryzae. In each case, the RTBV-MVIGS system gave rise to a discernible phenotype indicating the silencing of the respective target gene using condition III (temperature 28°C, humidity 80% and 1mM MES and 20µM acetosyringone in secondary agrobacterium culture), which revealed the robustness of this gene silencing system for rice.

Formulasi Bakteri Filosfer Padi dan Aplikasinya untuk Mengendalikan Penyakit Hawar Daun Bakteri

Xanthomonas oryzae pv.oryzae is a casual agent of bacterial leaf blight disease (BLB) of rice. The disease can infect every phases of plant growth and can reduce rice production. In the previous study we have isolated nonpathogenic phyllosphere bacteria against X. oryzae pv.oryzae. For further study, in the present work we developed the formulation of the phyllosphere bacteria and tested their effectiveness against BLB in greenhouse trials. Out of three alternative medium used in culturing bacterial cell biomass, it was revealed that potato broth served as the best medium in comparison with skim milk molasses and bran extract. Formulation of phyllosphere bacteria was conducted by using of talc as main carrier, i.e. approximately 109 cfu g-1of main carrier. Application of the formula on rice leaves indicated that BFV 60, BFF 69, BFR 203 and BFR 153 were the best formula for controlling BLB and were able to reduce disease incidence up to 40.73%, 39.72%, 39.26%, and 28.07%, respectively

Overexpression of MoSM1, encoding for an immunity-inducing protein from Magnaporthe oryzae, in rice confers broad-spectrum resistance against fungal and bacterial diseases

Potential of MoSM1, encoding for a cerato-platanin protein from Magnaporthe oryzae, in improvement of rice disease resistance was examined. Transient expression of MoSM1 in rice leaves initiated hypersensitive response and upregulated expression of defense genes. When transiently expressed in tobacco leaves, MoSM1 targeted to plasma membrane. The MoSM1-overexpressing (MoSM1-OE) transgenic rice lines showed an improved resistance, as revealed by the reduced disease severity and decreased in planta pathogen growth, against 2 strains belonging to two different races of M. oryzae, causing blast disease, and against 2 strains of Xanthomonas oryzae pv. oryzae, causing bacterial leaf blight disease. However, no alteration in resistance to sheath blight disease was observed in MoSM1-OE lines. The MoSM1-OE plants contained elevated levels of salicylic acid (SA) and jasmonic acid (JA) and constitutively activated the expression of SA and JA signaling-related regulatory and defense genes. Furthermore, the MoSM1-OE plants had no effect on drought and salt stress tolerance and on grain yield. We conclude that MoSM1 confers a broad-spectrum resistance against different pathogens through modulating SA- and JA-mediated signaling pathways without any penalty on abiotic stress tolerance and grain yield, providing a promising potential for application of MoSM1 in improvement of disease resistance in crops.

Peningkatan Mutu Fisiologis dan Daya Simpan Benih serta Ketahanan Patogen dan Agen Hayati pada Benih Padi Berpelapis

<p><em></em><em>ABSTRACT<br /><br />Xanthomonas oryzae pv. oryzae (Xoo), is a seedborne pathogen causing bacterial leaf blight (BLB) disease, and reduces the quality of seed and rice production. One of the efforts to control the BLB disease and to improve the quality Xoo infected seeds is the seed coating technique enriched with biological agents. The experiment was aimed to study the effect of coating on seed quality and storage life, as well as the Xoo and biological agents resistence (P. diminuta A6 and B. subtilis 5/B) on the seeds. The experiment was carried out from August 2011 to March 2012, using a split plot design with four replications. The main plot was storage period, i.e. 0, 1, 2, 3, 4, 5, 6, and 7 months. The sub plot was seed coating treatment consisted of negative control (healthy seed); positive control (seeds contaminated with Xoo); seed infested with biological agens; alginate 3% + 1% peat + biological agents; arabic gum 3% + 1% gypsum + biological agents; CMC 1.5% + 1% talc + biological agents; and bactericide streptomycin sulfat 20%. The coated seeds were stored an air-conditioned room (18-20 °C, RH 48-50%). The results showed that the treatments were able to maintain seeds quality during storage, i.e. germination percentage, uniformity percentage, and vigor index, better than those of the positive control. The P. diminuta A6 was still presence (0.08 x 106 cfu mL-1) in seeds coated after 7 month storage, and the B. subtilis 5/B was still presence (0.07 x 106 cfu mL-1) up to 6 month storage with 3% arabic gum + 1% gypsum + biological agents. <br /><br />Keywords: Bacillus subtilis 5/B, Pseudomonas diminuta A6, seed quality, storage space, Xanthomonas oryzae pv. oryzae<br /><br /></em><em> </em></p>

Population genomic insights into variation and evolution of Xanthomonas oryzae pv. oryzae

Xanthomonas oryzae pv. oryzae ( Xoo) is a serious pathogen of rice causing bacterial leaf blight disease. Resistant varieties and breeding programs are being hampered by the emergence of highly virulent strains. Herein we report population based whole genome sequencing and analysis of 100 Xoo strains from India. Phylogenomic analysis revealed the clustering of Xoo strains from India along with other Asian strains, distinct from African and US Xo strains. The Indian Xoo population consists of a major clonal lineage and four minor but highly diverse lineages. Interestingly, the variant alleles, gene clusters and highly pathogenic strains are primarily restricted to minor lineages L-II to L-V and in particularly to lineage L-III. We could also find the association of an expanded CRISPR cassette and a highly variant LPS gene cluster with the dominant lineage. Molecular dating revealed that the major lineage, L-I is youngest and of recent origin compared to remaining minor lineages that seems to have originated much earlier in the past. Further, we were also able to identify core effector genes that may be helpful in efforts towards building durable resistance against this pathogen.

Comparative Efficacy of Different Chemical Treatments for Paddy Blast, Brown Leaf Spot and Bacterial Leaf Blight Diseases in Rice (Oryza Sativa L.)

Paddy blast, brown leaf spot and bacterial leaf blight of rice are the most devastating diseases of rice worldwide causing serious threats to food security. For the purpose field trials were conducted for the evaluation of different available fungicides at Rice Research Institute, Kala Shah Kaku during season of 2016. Application of different fungicide to control the disease and their effect on paddy yield under field condition were studied. The results showed that fungicide application not only controlled the disease but also improved the paddy yield as compared to control. In this study, Amistar Top 325 SC performed best to control the Paddy blast that leaf to high yield. In the case of Brown leaf spot, application of Switch DF 80 WG revealed the lowest incidence of disease along with highest protection value. Similarly, Nativo was most effective to control the Bacterial Leaf Blight incidence. Conclusively, these chemical can be used to control the studied bacterial and fungal diseases for high paddy yield.

Pathogenicity of Xanthomonas campestris pv. allii causing bacterial leaf blight of onion in sudan and antibacterial efficacy of plant extracts

Bacterial leaf blight of onion, caused by Xanthomonas campestris pv. allii, is a new disease of green bulb onion in Sudan. A study was conducted to test pathogenicity of the causative agent of onion bacterial leaf blight and evaluate the efficacy of certain plant extracts against the pathogen. Antibacterial activity of aqueous ethanolic plant extracts of desert rose (Adenium obesum), eucalyptus (Eucalyptus microtheca), button wood (Conocarpus erectus), tamarind (Tamarindus indica) and mesquite (Prosopis julifora), at different concentrations, was assayed in vitro by well diffusion technique. The bacterium X. campestris pv. allii was isolated from leaf lesions and its pathogenicity was confirmed on onion leaves. There were significant differences between the extracts in their effect on bacterial growth and the best results were obtained at a high concentration (420 ppm) of plant extracts. Among the test plant extracts, mesquite extract revealed a high anti-bacterial activity with inhibition zone up to 38.6 mm. It was followed by eucalyptus extract with inhibition zone of 38.3mm, button wood and tamarind with inhibition zone of 38 mm each. Desert rose extract displayed lower inhibition zone of 20.2 mm as dcompare to the standard control of stryptomicin having inhibition zone of 36 mm. Thus plant extracts of eucalyptus, mesquite, button wood, and tamarind were promising and may help in the non-toxic, eco-friendly management of onion bacterial leaf blight disease.

Salicylic acid-induced accumulation of biochemical components associated with resistance against Xanthomonas oryzae pv. oryzae in rice

ABSTRACTSeed treatment and foliar sprays of salicylic acid (SA) provided protection in rice against bacterial leaf blight (BLB) caused by bacterial Xanthomonas oryzae pv. oryzae (Xoo). Treatment of rice with exogenous SA reduced disease severity by more than 38%. Superoxide anion production and hypersensitive response increased approximately 28% and 110% at 6 and 48 h after Xoo inoculation, respectively, for plants treated with SA. Moreover, the Xoo in treated rice plants grew more slowly, resulting in a population that was half of that observed in the control. Fourier transform infrared spectroscopy analysis revealed that the higher ratios of 1233/1517, 1467/1517, and 1735/1517 cm−1 observed in treated rice suggested alteration of monomer composition of lignin and pectin in the rice cell wall. Exogenous SA-treated rice had more amide I β-sheet structure and lipids as shown by the peaks at 1629, 2851, and 1735 cm−1. These biochemical changes of rice treated with SA and inoculated with Xoo were related to primed resistance of the rice plants to BLB disease.

Marker Assisted Selection for Bacterial Leaf Blight Rice Mutant Lines Resistant

Induction of mutation using gamma rays for improving of Mira-1 rice variety has been conducted.Rice mutant lines M2 generation have been obtained from mutation by the doses of 25, 50, 75, 100, 150 and200 Gy of gamma rays. Selection of mutant lines tolerant to the disease was only observed in the field neithergenetically. Marker assisted selection is a tool to obtain a new rice variety tolerant to the disease of bacterialleaf blight (BLB) genetically. Xanthomonas oryzae pv.oryzae (Xa) was the pathogen of BLB, and the identificationof rice mutant lines which were containing of Xa5, Xa13 and Xa21 genes have been done using PolymeraseChain Reaction ( PCR ) method. The result showed that one mutant line, and four mutant lines from mutationby the doses of 25 Gy and 150 Gy were containing Xa5, Xa13 and Xa21 genes the same as that of Code ricevariety as positive control, and none in Kencana Bali rice variety as negative control. Mira-1 rice variety as theparent plant was only contains Xa5 and Xa21 genes. The doses of 50 Gy and 100 Gy were very affective onremoving of all bands for identification of those genes. The purpose of this research was to obtain the mutantlines which were contain of those Xa genes as indicator for resistant to BLB disease genetically.

Identification of resistance sources against bacteria blight of cotton caused by Xam race no. 18

Cotton, “king of fibres” enjoys a pre-eminent status among all cash crops in the country, being the principal raw material for a flourishing textile industry. Among the various diseases occurring on cotton, the foliar disease bacterial blight caused by Xanthomonas axonopodis pv . malvacearum is gaining more importance in recent years because of their increasing incidence. These have been known to occur on all the various cultivated and wild species of cotton in Maharashtra, since many years, in an epiphytotic form on commercially grown varieties, which leads to severe defoliation and substantial yield lossess. Among the 221 cultivated genotypes screened for resistance against bacterial leaf blight disease under field conditions, 80 genotypes showed immune reaction. Further, 69 genotypes were resistant, 13 genotypes were moderately resistant, The 19 entries showed the moderately susceptible reaction and 40 entries showed the susceptible reaction to the bacterial blight disease.

English

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) has now become one of major rice diseases. During recent years, its occurrence has increased in Pakistan, particularly in ‘Kallar tract’ which is well-known for quality rice cultivation. Development of new resistant varieties by utilizing the available resistant gene-pool is most reliable breeding technique for the plant breeders. The present study was conducted to explore the genetic resources regarding presence and absence of BLB resistance genes Xa4 , xa5 and Xa21 through DNA marker technology. Effectiveness of Xa21 followed by xa5 and Xa7 genes has been reported to confer more resistance level for BLB in traditional rice belt of Pakistan. For this purpose, eighty (80) rice genotypes comprising of diverse origin including three isogenic lines viz., IRBB4 (carrying Xa4 ), IRBB5 (carrying xa5 ) and IRBB21 (carrying Xa21 ) as positive resistant gene checks and IR24 (carrying none of these) as negative gene check were genotyped. DNA fingerprinting results indicated the presence of Xa4 gene in 41 entries, while 14 lines were positive for xa5 gene. Only one local line was carrying Xa21 gene along with Xa4 . Thus, the present study will not only be helpful for rice breeders to develop new rice varieties carrying disease resistant genes, but will also provide the donors to incorporate / pyramid disease resistant genes in popular rice varieties like Super Basmati and Basmati 515 which are susceptible to BLB disease. Keywords: Molecular screening, rice germplasm, Xa4, xa5 and Xa21 genes, bacterial leaf blight

Pengujian Daya Hasil dan Ketahanan Penyakit Hawar Daun Bakteri Tanaman Padi Hibrida

ABSTRACT<br /><br />Hybrid rice varieties is an alternative technology to improve productivity of low land rice. The results of previous studies have identified and found the male sterile lines Wild Abortive type and Kalinga are resistant to bacterial leaf blight pathotype III, IV and VIII. The objectives of the research were to obtain information on agronomic characters, yield evaluation, genetic parameters, and repeatability information. The experiment was conducted in two locations namely Muara and Indramayu experimental stations. The design used was a Randomized Complete Block Design with three replication at each site. Each replicate consisted of 17 hybrid rice and three check varieties. The results from locations showed that genotype BI485A/BP1 (IR53942) has the highest yield of 5.8 ton ha-1. The coefficient of genetic and phenotypic diversity of six agronomic characters was low. The repeatability for seven character observed were low, except for days to flowering. The scoring value of bacterial leaf blight disease in Indramayu showed that nine genotypes exhibit resistance.<br /><br />Keywords: cytoplasmic male sterile lines, disease resistance <br /><br />

Application of Bioameliorant and Biofertilizers to Increase the Soil Health and Rice Productivity

The major rice intensity of diseases in Indonesia was increased significantly and has caused a yield loss of up to 20–30%. The experiments had been conducted to investigate the effect of bioameliorant or composted straw (CS) combined with consortia of biofertilizers (CB) and biocontrol agent to restore the soil health and promote the induced systemic resistance (ISR) for increasing the rice productivity. The experiment arranged as randomized block design consisted of 12 treatments (0, 2.5, 5.0 and 7.5 ton of CS per ha combined with 400 g of CB and 200 g inoculant of CB + 200 g inoculant of Trichoderma sp and was provided with three replications. The experimental results revealed that application of 2.5–7.5 ton per ha of bioameliorant combined with 400 g per ha of CB and 400 g Trichoderma sp has increased the ISR and enhanced the rice productivity significantly. The brown spot, sheath rice blight and bacterial leaf blight diseases were reduced from 16.7% to 3.3–8.0%, 20% to 4–10%, 24% to 2.7–4.7% and 20.7% to 8–14.0%, respectively at 7 weeks after transplanting. In addition, the rice grain yield was increased from about 7.1 ton ha−1 to 7.9–10.1 ton per ha.

Determination of Pathotypes from Indonesian Xanthomonas oryzae Pv. Oryzae Population causing Bacterial Leaf Blight and their Reactions on Differential Rice

The objective of this work was to study the virulence of 15 Xanthomonas oryzae pv. oryzae (Xoo) isolates collected in three provinces in Indonesia (North Sumatra, South Sumatra, and South Sulawesi) based on five Indonesian differential rice genotypes and 10 near isogenic lines (NILs) that have been known to differ in their resistance to bacterial leaf blight (BLB), in a greenhouse assessment. In addition, this study also aims to monitor the responses of 31 rice genotypes (21 NILs, five differentials, five improved cultivars) to BLB disease in a field experiment. The 15 isolates showed different virulence patterns on the NILs ’ genotypes with a single resistance gene indicating the pathogen diversity. Eight different pathotypes were present, as demonstrated by a particular virulence pattern of each isolate on the genotypes. Determination of Xoo pathotype revealed that Xoo pathotypes responded differently based on their reaction to NILs and Indonesian differential genotypes. The field assessment demonstrated the incidence and severity of BLB disease on rice genotypes ranging from 25% to 100% and 5.5% to 72.91%, respectively, while the mean disease index ranged from 1.15% to 72.9%. The disease response varied among rice genotypes. IRBB50 (Xa4+xa5) , IRBB51 ( Xa4+xa13) , IRBB52 ( Xa4+Xa21) , IRBB53 ( Xa4+Xa21) , IRBB56 ( Xa4+xa5+xa13) , IRBB57 ( Xa4+xa5+Xa21) , IRBB59 ( Xa4+xa13+Xa21), IRBB64 ( Xa4+xa5+Xa7+Xa21) , IRBB66 ( Xa4+xa5+Xa7+xa13+Xa21) , IRBB7( Xa7) , Angke ( Xa4+xa5) and Code (Xa4+Xa7) were revealed to be highly resistant to the BLB pathogen. These genotypes have potential as genetic material for the pyramiding of several resistance genes for the development of rice resistance to BLB disease in Indonesia.

Ketahanan Berbagai Kultivar Padi Lokal terhadap Penyakit Hawar Daun Bakteri

Bacterial leaf blight disease caused by Xanthomonas oryzae pv. oryzae is an important rice disease in Indonesia, including in South East Sulawesi. The use of resistant varieties is one of the effective and environmentally friendly control strategies to suppress the disease. This study aimed to determine the level of resistance of some local rice varieties of South and Southeast Sulawesi against Xanthomonas oryzae pv. oryzae pathotypes IV, VIII and X. The study was conducted in a screen house involving 3 bacterial pathotypes and 11 local rice cultivars. Shearing method was used for inoculation of bacteria to leaf on vegetative and generative phases. Disease incidences were measured 3 weeks after inoculation, and the data was further used to determine the level of resistance of the tested rice cultivars. The results showed that incubation period of the disease was longer on Kelaca cultivar compared to other cultivars. On vegetative phase, this cultivar showed moderate resistant to pathotypes IV and X, and highly resistant to patotype VIII, whereas on the generative phase it showed moderate resistant to pathotypes IV and VII, and highly resistant to pathotype X. Therefore, Kelaca cultivar can be recommended for endemic areas of leaf blight in South and Southeast Sulawesi

English

The Bacterial Leaf Blight (BLB) disease of rice caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the main reasons limiting production of rice in Asia ensuing to an average of 20 to 30% and in some Asian countries, up to 50% rice yield losses .The disease, when occurs in severe condition on susceptible cultivars, causes 74 to 81% yield losses (Srinivasan and Gnanamanickam, 2005). It was reported that yield losses can be 100% in Basmati rice at tillering stage (Mannan et al., 2009). Cultural practices, chemical control or resistant varieties are optional strategies for the control of plant diseases. The chemical control of BLB is impractical in the monsoon climatic conditions of Asia (Agrawal et al., 2005). Furthermore, no effective bactericide is commercially available for disease control. Therefore, the preferred strategy for disease management is through varietal resistance (Naveed et al., 2010). The manipulation of host resistance has been shown to be the only and most reliable method to manage this disease. Globally, to date, 39 Xa genes (28 dominant and 11 recessive) conferring resistance against Xoo have been identified (Chen et al., 2011; Zhang et al., 2014). These identified genes were evaluated in different countries against their indigenous Xoo populations to deploy in local germplasm for BLB resistance. The response of 23 lines like 10 NILs and 13 pyramids was evaluated against BLB under field conditions in Vietnam. The resistance gene xa13 and Xa14 were susceptible, Xa4 and xa5 were moderately susceptible and the rest were moderately resistant to BLB. Among the pyramids, Xa4+xa5+xa13+Xa21, Xa4+Xa7+Xa21 and xa5+Xa7+xa13 had short lesion length and low diseased leaf area (Loan et al., 2006). Three gene pyramid (xa5+xa13+Xa21) in variety Sawarna was transferred to Jalmagna, a popular deep-water variety in India, which exhibited a high level of resistance against BLB (Pradhan et al., 2015). However, the durability of resistance depends upon the prevalence of pathogen races in time and space. A lot of research has been done on the evaluation of rice genotype (Khan et al., 2009), virulence reaction of local Xoo isolates (Mannan et al., 2009), molecular screening of local germplasm against a specific R gene (Abbasi et al., 2011) and evaluation of resistance genes in rice against local isolates of Xoo (Khan et al., 2012) in Pakistan. But for the development of durable resistant cultivar, it is of prime importance to screen all available resistant genes either single or in combination against all prevailing 29 pathotypes of Xoo Pak. J. Agri. Sci., Vol. 53(2), 365-370; 2016 ISSN (Print) 0552-9034, ISSN (Online) 2076-0906 DOI: 10.21162/PAKJAS/16.5357 http://www.pakjas.com.pk