Characterization of a quantitative trait locus region for tungro resistance in advanced introgression lines of rice
2012
Waing, F.P., Philippine Rice Research Inst. Maligaya, Science City of Mu�oz, Nueva Ecija (Philippines). Plant Breeding and Biotechnology Div. | Fernando, T.C., Philippine Carabao Center, Science City of Munoz, Nueva Ecija (Philippines) | Alberto, R.T., Central Luzon State Univ., Science City of Munoz, Nueva Ecija (Philippines) | Romero, G.O., Monsanto Philippines, 7th Ayala Life-FGU Center, Madrigal Business Park, Alabang-Zapote Road, Alabang, Muntinlupa City (Philippines) | Tabanao, D.A., Philippine Rice Research Inst. Maligaya, Science City of Mu�oz, Nueva Ecija (Philippines). Plant Breeding and Biotechnology Div.
Tungro is the most economically important viral disease of rice in the Philippines. Its severe occurrence can cause staggering if not complete yield loss. Incorporating tungro resistance is an appropriate breeding target to secure farmers' yield with resistant varieties especially in tungro hotspot areas. In this study, the authors aimed to: 1) infer the haplotype of the introgression region in backcross lines derived from Indian landrace, ARC11554, 2) analyze the resistance of these lines to tungro and 3) determine the extent of recovery of recurrent parent genome in the backcross lines. The tungro resistance found in ARC11554, was previously localized on the short arm of rice chromosome 4 flanked by SSR markers RM8213 and RM3471 through quantitative trait loci (QTL) analysis. A total of 55 advanced introgression lines (11 BC2F6 and 44 BC4F4) in NSIC Rc138 background that were previously screened for their reaction to tungro were used for haplotype and phenotypic characterization. Twenty-two lines, which had at least six SSR alleles from ARC 11554 out of 12 markers in the 0.18 to 10.02 Mb region, were selected for further characterization. These lines were screened for tungro resistance following the forced inoculation method which resulted to decrease index rating ranging from 1.3 to 4.6 (resistant to moderately resistant) at 28 days after inoculation. Genome-index analysis was also carried out using 55 SSRs and corroborated the strong similarity of these lines to their recurrent parent based on marker similarity: 77.8-89.1% for BC2F6 and 85.2-92.7% for BC4F4. The combination of morphological and marker-assisted selection strategies is more efficient and reliable in the evaluation of tungro resistance than conventional visual observation (phenotyping) alone.
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