Characterization of quantitative trait loci (QTLs) in cultivated rice contributing to field resistance to sheath blight (Rhizoctonia solani)
Tóm tắt
Sheath blight, caused by Rhizoctonia solani, is one of the most important diseases of rice. Despite extensive searches of the rice germ plasm, the major gene(s) which give complete resistance to the fungus have not been identified. However, there is much variation in quantitatively inherited resistance to R. solani, and this type of resistance can offer adequate protection against the pathogen under field conditions. Using 255 F4 bulked populations from a cross between the susceptible variety ‘Lemont’ and the resistant variety ‘Teqing’, 2 years of field disease evaluation and 113 well-distributed RFLP markers, we identified six quantitative trait loci (QTLs) contributing to resistance to R. solani. These QTLs are located on 6 of the 12 rice chromosomes and collectively explain approximately 60% of the genotypic variation or 47% of the phenotypic variation in the ‘Lemont’x‘Teqing’ cross. One of these resistance QTLs (QSbr4a), which accounted for 6% of the genotypic variation in resistance to R. solani, appeared to be independent of associated morphological traits. The remaining five putative resistance loci (QSbr2a, QSbr3a, QSbr8a, QSbr9a and QSbr12a) all mapped to chromosomal regions also associated with increased plant height, three of which were also associated with QTLs causing later heading. This was consistent with the observation that heading date and plant height accounted for 47% of the genotypic variation in resistance to R. solani in this population. There were also weak associations between resistance to R. solani and leaf width, which were likely due to linkage with a QTL for this trait rather than to a physiological relationship.
Tài liệu tham khảo
Groth DW, Nowick EM (1992) Selection for resistance to rice sheath blight through number of infection cushions and lesion type. Plant Dis 76:721–723
Hashiba T, Uchiyamada H, Kimura K (1981) A method to estimate the disease incidence based on the height of the infected parts in rice sheath blight disease. Ann Phytopathal Soc Jpn 47:194–198
IRRI (1980) Descriptors for rice (Oryza sativa L.) International Rice Research Institute Los Banos, The Philippines
Kikuo W, Oro S, Kido Y (1983) The syringe inoculation method for selecting rice plants resistant to sheath blight, Rhizoctonia solani Kuhn. Jpn J Trop Agric 27:131–139
Li ZK, Pinson SRM, Stansel JW, Park WD (1995) Identification of two major genes and quantitative trait loci (QTLs) for heading date and plant height in cultivated rice (Oryza sativa L.). Theor Appl Genet 91:374–381
Marchetti MA (1983) Potential impact of sheath blight on yield and milling quality of short statured rice lines in the Southern United States. Plant Dis 67:162–165
Marchetti MA, Bollich CN (1991) Qualification of the relationship between sheath blight severity and yield loss in rice. Plant Dis 75:773–775
Marchetti MA, McClung AM (1994) Inheritance of sheath blight resistance in progeny of the cross RU8703196/‘Rosemont’. In: Proc 25th Rice Technal Work Group Meet, Texas Agricultural Experiment Station, Texas A&M Univ, College Station, Tex. (in press)
SAS Institute (1987) SAS/STAT guide for personal computers version 6. SAS Institute, Cary, N.C.
Sha XY (1987) Genetic studies on resistance to sheath blight (Thanatephorus cucumeris Frank Donk) in eight indica rice varieties. MSc thesis. Nanjing Agric Univ, PR China
Xie QJ, Rush MC, Cao J (1990) Somaclonal variation for disease resistance in rice (Oryza sativa L.). In: Grayson BT, Green MB, Copping LG (eds) Pest management in rice. Elsevier, New York, pp 491–509