Characterization of New Races of Xanthomonas oryzae pv. oryzae in Mali Informs Resistance Gene Deployment

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae represents a severe threat to rice cultivation in Mali. Characterizing the pathotypic diversity of bacterial populations is key to the management of pathogen-resistant varieties. Forty-one X. oryzae pv. oryzae isolates were collected between 2010 and 2013 in the major rice growing regions in Mali. All isolates were virulent on the susceptible rice variety Azucena; evaluation of the isolates on 12 near isogenic rice lines, each carrying a single resistance gene, identified six new races (A4 to A9) and confirmed race A3 that was previously reported in Mali. Races A5 and A6, isolated in Office du Niger and Sélingué, were the most prevalent races in Mali. Race A9 was the most virulent, circumventing all of the resistance genes tested. Xa3 controlled six of seven races (i.e., 89% of the isolates tested). The expansion of race A9 represents a major risk to rice cultivation and highlights the urgent need to identify a local source of resistance. We selected 14 isolates of X. oryzae pv. oryzae representative of the most prevalent races to evaluate 29 rice varieties grown by farmers in Mali. Six isolates showed a high level of resistance to X. oryzae pv. oryzae and were then screened with a larger collection of isolates. Based on the interactions among the six varieties and the X. oryzae pv. oryzae isolates, we characterized eight different pathotypes (P1 to P8). Two rice varieties, SK20-28 and Gigante, effectively controlled all of the isolates tested. The low association observed among races and pathotypes of X. oryzae pv. oryzae suggests that the resistance observed in the local rice varieties does not simply rely on single known Xa genes. X. oryzae pv. oryzae is pathogenically and geographically diverse. Both the races of X. oryzae pv. oryzae characterized in this study and the identification of sources of resistance in local rice varieties provide useful information to inform the design of effective breeding programs for resistance to bacterial leaf blight in Mali.

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PEMANFAATAN PIRAMIDA GEN KETAHANAN TERHADAP PENYAKIT HAWAR DAUN BAKTERI DALAM MENDUKUNG PERAKITAN VARIETAS UNGGUL PADI Application of Gene Pyramiding For Resistance to Bacterial Leaf Blight to Develop New Rice Variety

Jurnal Penelitian dan Pengembangan Pertanian ◽

10.21082/jp3.v39n1.2020.p11-20 ◽

2020 ◽

Vol 39 (1) ◽

pp. 11

Author(s):

Fatimah Fatimah ◽

Joko Prasetiyono

Keyword(s):

Molecular Marker ◽

Rice Variety ◽

Gene Pyramiding ◽

Leaf Blight ◽

Rice Production ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Yield Potential ◽

Rice Varieties ◽

Marker Assisted Backcrossing

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv oryzae (Xoo) is an important bacterial disease and very destructive to rice plant. BLB decreased rice production from 20%-30% up to 80%. Host-plant resistance is a cost-effective and environmentally safe approach to reduce yield loss. However the development of new rice variety by conventional selection would take several years. The genetic improvement in rice production considered as a vital program in order to ensure national food security. The availability of corresponding molecular marker makes it more precision and efficient by reducing the time required for selection. This present article highlights the molecular approach in breeding for BLB disease resistant rice varieties. In detail, it will be discussed the application of molecular marker assisted backcrossing and pyramiding gene resistance offered breeders to accelerate the rice breeding program for resistance to BLB. The pyramiding of three resistance BLB genes (xa5, Xa7, and Xa21and one gene (Xa4) as a background into two elite indica rice varieties, Ciherang and Inpari 13, was introduced successfully. The combining of conventional breeding, marker assisted backcrossing, disease evaluation, agronomic performance and yield has led the significant resistance of pyramid lines to Xoo Race III, IV and VIII in vegetative and generative phase while their yield potential was maintained (6-7 ton/ha). The current status of Ciherang-HDB and Inpari 13-HDB pyramid lines is the production of nucleoseeds and breeder seeds. This broad spectrum and durable resistance characteristic may help in controlling BLB disease in different region of Indonesia and it will facilitate the rice self-sustainability program.Keywords: Rice, gene pyramiding, plant breeding, molecular marker. AbstrakPenyakit hawar daun bakteri (HDB) yang disebabkan oleh Xanthomonas oryzae pv oryzae (Xoo) merupakan penyakit penting pada tanaman padi karena dapat menurunkan produksi padi rata-rata 20-30% bahkan dapat mencapai 80%. Penggunaan varietas tahan merupakan cara pengendalian yang paling efektif, ramah lingkungan, dan mudah dilakukan. Namun pengembangan varietas unggul baru melalui seleksi konvensional memerlukan waktu lebih lama. Perbaikan varietas padi perlu terus dikembangkan dalam mendukung ketahanan pangan dan kemandirian pangan nasional. Tersedianya marka molekuler membantu proses pemuliaan tanaman menjadi lebih presisi dan lebih efisien sehingga mengurangi waktu seleksi pada tanaman progeni. Tulisan ini memfokuskan pendekatan molekuler dalam pemuliaan varietas tahan penyakit HDB melalui piramida gen ketahanan untuk mempercepat progam pemuliaan padi tahan penyakit HDB. Kegiatan menggabungkan tiga gen ketahanan (xa5, Xa7, dan Xa21) dan satu gen (Xa4) sebagai background ke dalam padi varietas Ciherang dan Inpari-13 telah berhasil dilakukan. Melalui penggabungan beberapa pendekatan yaitu pemuliaan konvensional dan silang balik berbantu marka, evaluasi penyakit dan keragaan agronomi serta komponen hasil telah menunjukkan peningkatan ketahanan yang nyata pada galur-galur piramida Ciherang HDB dan Inpari-13 HDB pada tiga ras Xoo (Ras III, IV, dan VIII), baik pada fase vegetatif maupun generatif dengan potensi hasil tidak berbeda nyata dengan tetuanya (6-7 t/ha). Saat ini sudah diproduksi benih inti (NS) dan benih penjenis (BS) galur-galur piramida Ciherang HDB dan Inpari-13 HDB. Dengan demikian, galur-galur piramida memiliki spektrum yang luas dan mampu bertahan dalam jangka waktu lama sehingga dapat mengontrol penyakit HDB di berbagai wilayah Indonesia dan mendukung target pemerintah untuk mempertahankan swasembada beras secara berkelanjutan.Kata kunci: Padi, piramida gen, pemuliaan tanaman, marka molekuler.

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Response of a local rice variety Pandanwangi to infection of bacterial leaf blight Xanthomonas oryzae pv. oryzae strain III, IV, and VIII

IOP Conference Series Earth and Environmental Science ◽

10.1088/1755-1315/905/1/012068 ◽

2021 ◽

Vol 905 (1) ◽

pp. 012068

Author(s):

Hadiwiyono ◽

S H Poromarto ◽

S Widono ◽

R F Rizal

Keyword(s):

Rice Variety ◽

Leaf Blight ◽

Rice Production ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Artificial Inoculation ◽

Limiting Factors ◽

Bacterial Suspension ◽

West Java ◽

Local Cultivar

Abstract Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the limiting factors in rice production. A local cultivar, rice “Pandanwangi” is a superior variety much preferred and cultivated by the farmers in Cianjur, West Java, Indonesia. The information about the response of “Pandangwangi” to Xoo is still poorly understood. This paper reports the results of the evaluation of “Pandanwangi” response against BLB. This research was conducted in a greenhouse with artificial inoculation using Xoo strains III, IV, and VIII with bacterial suspension at 108 cfu.mL−1. The results showed that the response of cv Pandanwangi to Xoo infection was different from the strain of Xoo. “Pandanwangi” cultivar was susceptible to Xoo strain III and VIII and very susceptible to strain IV.

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Improved bacterial leaf blight disease resistance in the major elite Vietnamese rice cultivar TBR225 via editing of the OsSWEET14 promoter

PLoS ONE ◽

10.1371/journal.pone.0255470 ◽

2021 ◽

Vol 16 (9) ◽

pp. e0255470

Author(s):

Phuong Nguyen Duy ◽

Dai Tran Lan ◽

Hang Pham Thu ◽

Huong Phung Thi Thu ◽

Ha Nguyen Thanh ◽

...

Keyword(s):

Agronomic Traits ◽

Rice Variety ◽

Rice Cultivar ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

Transcription Activator ◽

Rice Varieties ◽

Sugar Transporters ◽

Blight Disease ◽

Mutant Lines

TBR225 is one of the most popular commercial rice varieties in Northern Vietnam. However, this variety is highly susceptible to bacterial leaf blight (BLB), a disease caused by Xanthomonas oryzae pv. oryzae (Xoo) which can lead to important yield losses. OsSWEET14 belongs to the SWEET gene family that encodes sugar transporters. Together with other Clade III members, it behaves as a susceptibility (S) gene whose induction by Asian Xoo Transcription-Activator-Like Effectors (TALEs) is absolutely necessary for disease. In this study, we sought to introduce BLB resistance in the TBR225 elite variety. First, two Vietnamese Xoo strains were shown to up-regulate OsSWEET14 upon TBR225 infection. To investigate if this induction is connected with disease susceptibility, nine TBR225 mutant lines with mutations in the AvrXa7, PthXo3 or TalF TALEs DNA target sequences of the OsSWEET14 promoter were obtained using the CRISPR/Cas9 editing system. Genotyping analysis of T0 and T1 individuals showed that mutations were stably inherited. None of the examined agronomic traits of three transgene-free T2 edited lines were significantly different from those of wild-type TBR225. Importantly, one of these T2 lines, harboring the largest homozygous 6-bp deletion, displayed decreased OsSWEET14 expression as well as a significantly reduced susceptibility to a Vietnamese Xoo strains and complete resistance to another one. Our findings indicate that CRISPR/Cas9 editing conferred an improved BLB resistance to a Vietnamese commercial elite rice variety.

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Molecular Detection of Resistance To Bacterial Leaf Blight on Conde Indonesian Rice Variety

ANNALES BOGORIENSES ◽

10.14203/ann.bogor.2018.v22.n1.27-34 ◽

2018 ◽

Vol 22 (1) ◽

pp. 27 ◽

Cited By ~ 1

Author(s):

Fatimah Fatimah ◽

Joko Prasetiyono ◽

Aqwin Polosoro ◽

Mushlihatun Baroya

Keyword(s):

Sequence Alignment ◽

Molecular Detection ◽

Nucleotide Substitution ◽

Gene Action ◽

Rice Variety ◽

Leaf Blight ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Cultivated Rice ◽

Similar Gene

Rice bacterial leaf blight (BLB) disease caused by Xanthomonas oryzae pv. oryzae (Xoo) affected grain yield and decreasing rice production in rice growing countries. Conde, Indonesian rice variety, exhibits high resistance to most of the Indonesian races of (BLB) and has been used in Indonesia for cultivated rice. This study was aimed to conduct the molecular detection between proximal markers in chromosome 6 and relative expression of Conde rice variety compare to IRBB7 in Xa7 region. The population screening, BLB evaluation and molecular detection around the Xa7 region were conducted. The results showed from the collection of individual recombinants between resistant and susceptible parents narrow the region containing the BTBPOZ domain. The sequence alignment of Xa7LD37 in two resistant and three susceptible cultivars demonstrated a perfect association. The sequence alignment in exon region of Loc_Os06g46240 in Nipponbare, IRBB7, and IR64 identified indel/SNPs in this region leading to nucleotide substitution and frameshift resulting in amino acid change between resistant and susceptible cultivars. It was predicted that Conde revealed the similar gene action with Xa7 gene for BLB that encodes a BTB POZ domain.

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Seleksi Lapang Ketahanan Beberapa Varietas Padi terhadap Infeksi Hawar Daun Bakteri Strain IV dan VIII

Buletin Plasma Nutfah ◽

10.21082/blpn.v17n2.2011.p80-87 ◽

2016 ◽

Vol 17 (2) ◽

pp. 80 ◽

Cited By ~ 2

Author(s):

Lina Herlina ◽

Tiur S. Silitonga

Keyword(s):

Oryza Sativa ◽

Block Design ◽

Leaf Blight ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Bacterial Cells ◽

Bacterial Strains ◽

Rice Varieties ◽

Resistance Reaction ◽

Index Of Severity

Field Selection on Several Rice Varieties for Resistance to Bacterial Leaf Blight strain IV and VIII. Bacterial leaf blight (BLB) on rice (Oryza sativa) caused by Xanthomonas oryzae pv. oryzae (Xoo) is the major obstruction for rice production. Powerful strategy to control BLB is generally conducted by planting resistant plant. Meanwhile, the main way to explore germplasm as the source of resistance gene is conducted by selection a wide rice varieties. Field selection for resistance to BLB on 150 rice-varieties (BB-Biogen collection) was conducted in 2009 in Cianjur. Three leaves and flag leaves of individual hills at vegetative and flowering stage were inoculated by clipping the leaf tip with scissors which had been connected with a suspension bottle of bacterial cells (109- 1010 cells/ml) of the isolates which represented bacterial groups (strain) IV and VIII, respectively. Each plant was inoculated with one race. Two weeks after inoculation, length of the lesion developed on the inoculated leaf was measured, as an index of severity of infection by BLB. This experiment was treated as Factorial-Randomized Completed Block Design (two factor-with 3 replications, respectively). The resistancyreaction to strain IV and VIII was observed as the variable tested, while the factors measured consists of plant-varieties and two bacterial strains. The results showed that 11 varieties with a resistance-reaction to Xoo strain IV, inwhich 5 varieties poses a consistent resistance-reaction, i.e: Pulu Bolong, Pelopor, Gombal, Barito and Kapuas. While resistancereaction to Xoo strain VIII obtained only one variety : IR42 (score-1), while 17 others showed intermediate resistancy (score-3). AbstrakPenyakit hawar daun bakteri (HDB) yang disebabkan oleh Xanthomonas oryzae pv. oryzae (Xoo) pada padi (Oryza sativa) merupakan faktor pembatas upaya peningkatan produksi padi. Pencarian gen-gen tahan terhadap HDB sangat diperlukan untuk pengendalian penyakit tersebut. Seleksi ketahanan terhadap HDB dilakukan di Cianjur pada MT 2009 terhadap 150 varietas padi koleksi Bank Gen, BB-Biogen. Isolat Xoo yang diuji adalah strain IV dan VIII. Inokulasi dilakukan dua kali, yaitu pada fase vegetatif dan generatif dengan cara menggunting 3-5 cm dari ujung daun dan daun bendera dengan gunting yang telah dihubungkan dengan botol berisi suspensi Xoo strain IV dan VIII (109-1010 sel/ml). Rancangan percobaan yang digunakan dalam penelitian ini adalah acak kelompok faktorial dengan tiga ulangan. Sebagai varietas pembanding tahan digunakan IRBB7 dan pembanding rentan varietas Kencana Bali. Reaksi ketahanan tertinggi terhadap Xoo strain IV ditunjukkan oleh 11 varietas terpilih dengan reaksi agak tahan, lima varietas di antaranya menunjukkan reaksi yang konsisten agak tahan, yaitu varietas Pulu Bolong, Pelopor, Gombal, Barito, dan Kapuas. Reaksi &lsquo;tahan&rsquo; terhadap Xoo strain VIII ditunjukkan oleh satu varietas introduksi IR42. Untuk varietas terpilih dengan reaksi &lsquo;agak tahan&rsquo; terdapat 17 varietas.

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Phenotype and genotype variability of interspecific rice lines related to bacterial leaf blight resistance (Xanthomonas oryzae pv. oryzae) character

Biodiversitas Journal of Biological Diversity ◽

10.13057/biodiv/d221001 ◽

2021 ◽

Vol 22 (10) ◽

Author(s):

SITI YURIYAH ◽

DEDY DARNAEDI ◽

TATANG MITRA SETIA ◽

GUT WINDARSIH ◽

Dwinita Wikan Utami

Keyword(s):

Resistance Gene ◽

Wild Rice ◽

Leaf Blight ◽

Oryza Rufipogon ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Yield Potential ◽

Interspecific Crosses ◽

Blight Resistance ◽

Wild Rice Species

Abstract. Yuriyah S, Darnaedi D, Setia TM, Windarsih G, Utami DW. 2021. Phenotype and genotype variability of interspecific rice lines related to bacterial leaf blight resistance (Xanthomonas oryzae pv. oryzae) character. Biodiversitas 22: 4123-4130. Wild rice species are the source of the gene pool for rice genetic diversity. The cross-species crosses (interspecific crosses) play an important role in breeding, namely in terms of expanding the diversity of desirable characters, such as disease resistance and improvement in yield potential. Currently, the genes from wild rice species have been successfully introgressed into cultivated rice so that they can overcome the rice production constraints, including the introgression of genes for the bacterial leaf blight (BLB) resistance. The purpose of this study was to analyze the variability of phenotype and genotype performance of lines derived from wild rice species for the character of resistance to BLB disease. A total of 33 selected backcross lines derived from wild rice species of O. rufipogon and O. glaberrima as the donor parents and 2 control varieties (resistant and susceptible to BLB disease), were used in this study. The evaluation of phenotype and genotype of resistance characters to BLB disease was carried out during a vegetative phase of the plant. The resistance evaluation was carried out in a greenhouse, while the genotype performance was analyzed using 4 STS markers linked to Xa4, Xa7, and Xa13 genes. The result of the phenotype evaluation showed that there were variations among the resistance of the tested lines. Three lines derived from a Situ Bagendit/Oryza rufipogon cross were resistant to all BLB races used in the testing. Those three lines indicated to have the allele of the Xa7 resistance gene based on the genotype performance which grouped with the Code variety that had the Xa7 resistance gene.

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Marker Assisted Screening of Nepalese rice for bacterial leaf blight (BLB) resistance

Nepal Journal of Biotechnology ◽

10.3126/njb.v3i1.14227 ◽

2015 ◽

Vol 3 (1) ◽

pp. 35-39 ◽

Cited By ~ 1

Author(s):

Resham Babu Amgai ◽

Raj Kumar Niroula ◽

Sumitra Pantha ◽

Shreya Singh Hamal ◽

Bishal Gole Tamang ◽

...

Keyword(s):

Resistance Gene ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

Limiting Factor ◽

Rice Varieties ◽

Resistant Gene ◽

Rice Landraces ◽

Sequence Tagged Sites ◽

Check Variety ◽

Simple Sequence

Bacterial Leaf Blight (BLB) is the most important yield limiting factor in Nepalese rice. BLB resistance rice varieties are highly demanding in the country. Breeding efforts for developing disease resistant depends on availability and use of resistant gene donors. Nepalese rice landraces could be the source of resistant gene. Therefore, ninety six Nepalese rice accessions were screened using eight Simple Sequence Repeats (SSR) markers and one Sequence Tagged Sites (STS) marker for presence and absence of BLB resistance gene. We have detected BLB resistance gene Xa-10 on five accessions, Xa-13 on six accessions, Xa-7 on 23 accessions, Xa-3 and Xa-4 on 52 accessions, Xa-5 on 25 accessions, Xa-8 on 30 rice accessions. No any rice accessions tested have Xa-21. Similarly, 17 rice accessions showed three and more than three BLB resistance genes. Presence of Xa-13 on susceptible check variety CNTRL-85033 confirmed that this resistant gene is not working in Nepalese rice field. Therefore, Nepal need to pyramide the BLB resistant genes for durable resistance.Nepal Journal of Biotechnology. Dec. 2015 Vol. 3, No. 1: 35-39

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The Resistance of Local Pigmented Rice Varieties against Bacterial Leaf Blight

Jurnal Perlindungan Tanaman Indonesia ◽

10.22146/jpti.46902 ◽

2019 ◽

Vol 23 (2) ◽

pp. 205

Author(s):

Tri Joko ◽

Kristamtini Kristamtini ◽

Sumarno Sumarno ◽

Rofiq Andriyanto

Keyword(s):

Rice Variety ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

Resistant Variety ◽

Bacterial Suspension ◽

Red Rice ◽

Black Rice ◽

Rice Varieties ◽

White Rice ◽

Progress Curve

Bacterial leaf blight (BLB) caused by Xanthomonas oryzae pv. oryzae (Xoo) is an important disease in rice plants worldwide, including in Indonesia. The use of resistant variety against BLB is the best effort in disease control because it is considered as the most effective and environmentally friendly. This study aimed to evaluate the resistance of local varieties, red rice (cv. Sembada Merah) and black rice (cv. Sembada Hitam), against Xoo compared to white rice variety (Ciherang), commonly cultivated by the farmers. The study was conducted in a greenhouse and arranged in Factorial of Completely Randomized Design (CRD) with 5 replications and 2 treatment factors: variety (Sembada Hitam, Sembada Merah, and Ciherang) and inoculation (with and without inoculated by Xoo bacterial suspension). Xoo inoculation was performed by clipping the leaves that close to the reproductive phase when the heading begins to be produced. The disease intensity and Area Under Disease Progress Curve (AUDPC) over two weeks were used to determine the level of resistance of the tested plant varieties. The results showed that black rice and red rice had better levels of resistance against BLB compared to white rice. At two weeks after inoculation, Sembada Hitam had the lowest AUDPC value followed by Sembada Merah, while the Ciherang had the highest AUDPC value and was categorized as a susceptible variety to Xoo.

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Molecular Detection of Resistance To Bacterial Leaf Blight on Conde Indonesian Rice Variety

ANNALES BOGORIENSES ◽

10.14203/ab.v22i1.337 ◽

2018 ◽

Vol 22 (1) ◽

pp. 27

Author(s):

Fatimah Fatimah ◽

Joko Prasetiyono ◽

Aqwin Polosoro ◽

Mushlihatun Baroya

Keyword(s):

Sequence Alignment ◽

Molecular Detection ◽

Nucleotide Substitution ◽

Gene Action ◽

Rice Variety ◽

Leaf Blight ◽

Xanthomonas Oryzae ◽

Bacterial Leaf Blight ◽

Cultivated Rice ◽

Similar Gene

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Uji Ketahanan Galur-galur Harapan Padi terhadap Penyakit Hawar Daun Bakteri (Xanthomonas oryzae pv. oryzae) Ras III, IV, dan VIII

Buletin Plasma Nutfah ◽

10.21082/blpn.v19n2.2013.p53-60 ◽

2016 ◽

Vol 19 (2) ◽

pp. 53

Author(s):

Siti Yuriyah ◽

Dwinita W. Utami ◽

Ida Hanarida

Keyword(s):

Molecular Biology ◽

Leaf Blight ◽

Oryza Rufipogon ◽

Xanthomonas Oryzae ◽

Resistance Test ◽

Bacterial Leaf Blight ◽

Rice Varieties ◽

Rice Germplasm ◽

Pure Cultures ◽

Different Levels

Resistance Test of Promising Rice Lines Against Bacterial Leaf Blight (Xanthomonas oryzae pv. oryzae) Race III, IV, and VIII. Siti Yuriyah, Dwinita W. Utami, and Ida Hanarida. Development of new superior rice varieties resistant to bacterial leaf blight (BLB) has been conducted through utilizing of a wide rice germplasm, from crossing between IR64 and Oryza rufipogon. The aim of this study is to get promising rice lines that resistant to BLB race III, IV, and VIII. The experiments were conducted at greenhouse and Laboratory of Molecular Biology, ICABIOGRAD Bogor, using of 13 promising rice lines that have different levels of resistance to inoculum from pure cultures of BLB race III, IV and VIII. Of these 13 rice lines, six lines showed resistance to race III (Bio5-AC-Blas/BLB-03, Bio62-AC-Blas/BLB-03, Bio111-BC-PIR7, Bio129-BC-WBC, Bio148-Mamol, and Bio154-Mamol-Dro), one line showed resistance to race IV (Bio154-Mamol-Dro), and one line showed resistance to race VIII (Bio5-AC-Blas/BLB-03), with severity rate 1.8 to 8.1%. Of these improve lines Bio5-AC-Blas/BLB-3 and Bio 111-BCPir- 7, were released as new rice varieties, namely Inpari HDB and Inpari Blas, respectively. AbstrakPerakitan varietas padi unggul baru tahan terhadap hawar daun bakteri (HDB) terus dilakukan melalui pemanfaatan sumber daya genetik yang luas. Saat ini telah dirakit galur-galur unggul yang berasal dari persilangan IR64 dan padi liar Rupifogon. Penelitian ini bertujuan untuk mengevaluasi ketahanan galur harapan padi terhadap penyakit HDB dari Ras III, IV, dan VIII. Percobaan dilakukan di rumah kaca dan Laboratorium Kelti Biologi Molekuler, BB Biogen, Bogor. Materi genetik yang digunakan adalah 13 galur harapan padi dan biakan murni dari Ras III, IV, dan VIII. Metode inokulasi dengan pengguntingan dan skoring ketahanan dilakukan sesuai dengan sistem penilaian dari Yashitola et al. (1997). Dari 13 galur padi harapan yang diuji, diperoleh enam galur tahan terhadap Ras III (Bio5-AC-Blas/BLB-03, Bio62-AC-Blas/BLB-03, Bio111- BC-PIR7, Bio129-BC-WBC, Bio148-Mamol-Dro, dan Bio154-Mamol-Dro), satu galur tahan terhadap Ras IV (Bio154-Mamol-Dro) dan satu galur tahan terhadap Ras VIII (Bio5-AC-Blas/BLB-03), dengan tingkat keparahan sebesar 1,8-8,1%. Dalam perkembangannya, dua dari galur harapan, yaitu galur Bio5-AC-Blas/BLB-03 dan Bio111-BC-Pir-7 disetujui untuk dilepas sebagai varietas Inpari HDB dan Inpari Blas.

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