QTL mapping for resistance to Bakanae disease in rice (Oryza sativa L.)

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2016, 2016
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DIVISION OF GENETICS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI-
DIVISION OF GENETICS INDIAN AGRICULTURAL RESEARCH INSTITUTE NEW DELHI-
Abstract
Rice is one of the most important staple food crops grown in diverse ecological conditions across the world. Its productivity is limited by various biotic and abiotic stresses. Among the biotic stresses, Bakanae or foot rot disease, caused by Fusarium fujikuroi (teleomorph: Gibberella fujikuroi, Sawada, Wollenweber) is one of the emerging diseases limiting productivity as well as quality. Among various options for the management of this disease, host plant resistance is considered to be the most cheapest and sustainable approach. Till date, there is limited progress in identifying sources of resistance against bakanae due to lack of reliable, reproducible and rapid assay to screen large numbers of germplasm against this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed a high-throughput screening protocol which involves soaking of rice seeds in fungal spore suspension (1.0×106 spores ml−1 ) for 24 hours at room temperature. Seedling growth at 30°/25° (±3)°C day/night temperature and 60/80 (±10)% day/night relative humidity in glasshouse gave the best results. Ninety-two rice germplasm were screened using new protocol which includes both Basmati and non-Basmati varieties. The screening revealed that, eight genotypes were highly resistant, four were resistant, thirty-three were found to be moderately resistant, fourteen moderately susceptible, thirteen susceptible and twenty genotypes highly susceptible to the Bakanae. Genotypes such as Pusa 1342, Athad apunnu, C101A51, Chandana, IR 58025B, Panchami, PAU 201 and Varun Dhan were found to be highly resistant, while BPT 5204, Himju, Peeli badam and Suphala were resistant. Genotypes, Pusa Basmati 1121, Heibao, Indira sona, Lal Basmati, PRR 78, Pungreila, Punjab Basmati 3, Pusa 1568, Pusa 33, Saathi, Sahpasand, SN 46, Sonasal, Suraniat, Swarna, Tetep, Type-3 and Tilak Chandan were highly susceptible to bakanae disease. The overall results indicated that all the Basmati genotypes were highly susceptible to Bakanae disease as compared to non-Basmati varieties. A mapping population of 168 F14 recombinant inbred lines derived from the cross between highly susceptible parent ‘Pusa Basmati 1121’ and highly 90 resistant parent ‘Pusa 1342’ was used for QTL mapping. The RIL population was screened for disease resistance with the fungal isolate ‘F250’ using the high throughput screening method. QTL mapping was performed using QTL IciMapping software v3.3. Single marker analysis identified seven marker loci linked to putative QTLs governing resistance to Bakanae disease. The phenotypic variation explained (PVE) by each QTL ranged from 8.73 % to 31.15 %. Highest phenotypic variance explained by RM10153 and lowest by RM411. Interval mapping identified four QTLs namely qBK1.1, qBK1.2, qBK1.3 and qBK3.1 for Bakanae disease resistance, explaining phenotypic variance 4.76, 24.74, 6.49 and 8.34 % with a LOD score of 3.76, 15.69, 6.48 and 3.31, respectively. Inclusive Composite Interval Mapping identified three QTLs i.e., qBK1.1, qBK1.2 and qBK1.3 with LOD scores of 2.73, 12.07 and 3.86, accounting for 4.76%, 24.74% and 6.49% of the total phenotypic variation, respectively. Among these, the major QTL qBK1.2 was mapped onto chromosome 1 in the marker interval of RM10153-RM5336. This is the first report on mapping QTLs governing Bakanae disease resistance in rice through Inclusive Composite Interval Mapping. An insilico search was done for the chromosomal interval based on the physical location of the flanking markers RM10153 and RM5336 for the presence of candidate defense responsive genes associated with Bakanae disease resistance using rice data base MSU-RAP. A total of 55 annotated genes were present in the 0.26 Mb region interval of the major QTL qBK1.2. Out of 55 annotated genes, 12 genes are associated with disease resistance were identified, which included genes associated with disease resistance, which may be potential candidates governing resistance to Bakanae disease.
Rice is one of the most important staple food crops grown in diverse ecological conditions across the world. Its productivity is limited by various biotic and abiotic stresses. Among the biotic stresses, Bakanae or foot rot disease, caused by Fusarium fujikuroi (teleomorph: Gibberella fujikuroi, Sawada, Wollenweber) is one of the emerging diseases limiting productivity as well as quality. Among various options for the management of this disease, host plant resistance is considered to be the most cheapest and sustainable approach. Till date, there is limited progress in identifying sources of resistance against bakanae due to lack of reliable, reproducible and rapid assay to screen large numbers of germplasm against this disease. To facilitate accurate, uniform and simultaneous screening of many rice accessions, we developed a high-throughput screening protocol which involves soaking of rice seeds in fungal spore suspension (1.0×106 spores ml−1 ) for 24 hours at room temperature. Seedling growth at 30°/25° (±3)°C day/night temperature and 60/80 (±10)% day/night relative humidity in glasshouse gave the best results. Ninety-two rice germplasm were screened using new protocol which includes both Basmati and non-Basmati varieties. The screening revealed that, eight genotypes were highly resistant, four were resistant, thirty-three were found to be moderately resistant, fourteen moderately susceptible, thirteen susceptible and twenty genotypes highly susceptible to the Bakanae. Genotypes such as Pusa 1342, Athad apunnu, C101A51, Chandana, IR 58025B, Panchami, PAU 201 and Varun Dhan were found to be highly resistant, while BPT 5204, Himju, Peeli badam and Suphala were resistant. Genotypes, Pusa Basmati 1121, Heibao, Indira sona, Lal Basmati, PRR 78, Pungreila, Punjab Basmati 3, Pusa 1568, Pusa 33, Saathi, Sahpasand, SN 46, Sonasal, Suraniat, Swarna, Tetep, Type-3 and Tilak Chandan were highly susceptible to bakanae disease. The overall results indicated that all the Basmati genotypes were highly susceptible to Bakanae disease as compared to non-Basmati varieties. A mapping population of 168 F14 recombinant inbred lines derived from the cross between highly susceptible parent ‘Pusa Basmati 1121’ and highly 90 resistant parent ‘Pusa 1342’ was used for QTL mapping. The RIL population was screened for disease resistance with the fungal isolate ‘F250’ using the high throughput screening method. QTL mapping was performed using QTL IciMapping software v3.3. Single marker analysis identified seven marker loci linked to putative QTLs governing resistance to Bakanae disease. The phenotypic variation explained (PVE) by each QTL ranged from 8.73 % to 31.15 %. Highest phenotypic variance explained by RM10153 and lowest by RM411. Interval mapping identified four QTLs namely qBK1.1, qBK1.2, qBK1.3 and qBK3.1 for Bakanae disease resistance, explaining phenotypic variance 4.76, 24.74, 6.49 and 8.34 % with a LOD score of 3.76, 15.69, 6.48 and 3.31, respectively. Inclusive Composite Interval Mapping identified three QTLs i.e., qBK1.1, qBK1.2 and qBK1.3 with LOD scores of 2.73, 12.07 and 3.86, accounting for 4.76%, 24.74% and 6.49% of the total phenotypic variation, respectively. Among these, the major QTL qBK1.2 was mapped onto chromosome 1 in the marker interval of RM10153-RM5336. This is the first report on mapping QTLs governing Bakanae disease resistance in rice through Inclusive Composite Interval Mapping. An insilico search was done for the chromosomal interval based on the physical location of the flanking markers RM10153 and RM5336 for the presence of candidate defense responsive genes associated with Bakanae disease resistance using rice data base MSU-RAP. A total of 55 annotated genes were present in the 0.26 Mb region interval of the major QTL qBK1.2. Out of 55 annotated genes, 12 genes are associated with disease resistance were identified, which included genes associated with disease resistance, which may be potential candidates governing resistance to Bakanae disease.
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T-9559
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