| Sumario: | Rice sheath blight (ShB), caused by the soilborne pathogen Rhizoctonia
solani, annually causes severe losses in yield and quality in many
rice production areas worldwide. Jasmine 85 is an indica cultivar that has
proven to have a high level of resistance to this pathogen. The objective
of this study was to determine the ability of controlled environment
inoculation assays to detect ShB resistance quantitative trait loci (QTLs)
in a cross derived from the susceptible cv. Lemont and the resistant cv.
Jasmine 85. The disease reactions of 250 F5 recombinant inbred lines
(RILs) were measured on the seedlings inoculated using microchamber
and mist-chamber assays under greenhouse conditions. In total, 10 ShBQTLs
were identified on chromosomes 1, 2, 3, 5, 6, and 9 using these two
methods. The microchamber method identified four of five new ShBQTLs,
one on each of chromosomes 1, 3, 5, and 6. Both microchamber
and mist-chamber methods identified two ShB-QTLs, qShB1 and qShB9-
2. Four of the ShB-QTLs or ShB-QTL regions identified on chromosomes
2, 3, and 9 were previously reported in the literature. The major
ShB-QTL qShB9-2, which cosegregated with simple sequence repeat
(SSR) marker RM245 on chromosome 9, contributed to 24.3 and 27.2%
of total phenotypic variation in ShB using microchamber and mistchamber
assays, respectively. qShB9-2, a plant-stage-independent QTL,
was also verified in nine haplotypes of 10 resistant Lemont/Jasmine 85
RILs using haplotype analysis. These results suggest that multiple ShBQTLs
are involved in ShB resistance and that microchamber and mistchamber
methods are effective for detecting plant-stage-independent
QTLs. Furthermore, two SSR markers, RM215 and RM245, are robust
markers and can be used in marker-assisted breeding programs to
improve ShB resistance.
|
|---|