ABSTRACT
Rice flour is useful as a substitute for wheat flour, however, to obtain fine flour, millers need special milling facilities, which increase the cost of milling. To reduce the milling cost, we developed a floury mutant line by irradiating gamma-rays to dry seeds of the japonica cultivar 'Hoshinoyume'. The line was registered as a new cultivar, 'Hoshinoko'. Genetical analysis of the floury trait was conducted using an F2 population derived from a cross between 'Hoshinoko' and 'Corbetti' (a japonica rice cultivar with normal endosperm), which indicated the involvement of a single recessive gene located near the RM163 marker on the long arm of rice chromosome 5, flanking flo4 identified by Kang et al. (2005). Sequence analysis of flo4 showed a two-bp (CA) insertion in the eighth exon of in 'Hoshinoko' compared to that of 'Hoshinoyume', which led to a frameshift mutation. The CAPS-based genotype of flo4 gene completely correlated to the phenotype of endosperm in two populations. This CAPS marker could be helpful for rice breeders to develop new cultivars harboring floury endosperm of the flo4-303 gene.
ABSTRACT
Speckled snow mold caused by Typhula ishikariensis is one of the most devastating diseases of winter wheat in Hokkaido, Japan and parts of the Pacific Northwest region of USA. Münstertaler is a winter wheat landrace from Switzerland that has very high resistance to snow mold and superior freezing tolerance. Quantitative trait loci (QTL) for resistance to speckled snow mold were identified in a doubled haploid population derived from a cross between Münstertaler and susceptible variety Ibis, both under field conditions and controlled environment tests. Composite interval mapping analysis revealed a major QTL on chromosome 5D from Münstertaler, and on chromosome 6B from Ibis. Flanking microsatellite marker cfd 29 for the QTL on chromosome 5D was about 5 cM distant from vernalization requirement gene Vrn-D1, suggesting that the QTL on chromosome 5D is located on a cold-stress-related gene cluster along with Vrn-D1 and freezing tolerance gene Fr-D1. The QTL on chromosome 6B from Ibis was located on the centromere region flanking QTn.mst-6B, which is reported to increase plant tiller number.
ABSTRACT
The influence of soil matric potential, cold-hardening temperature, and duration on resistance to speckled snow mold caused by Typhula ishikariensis in wheat was investigated. Six winter wheat lines were subjected to cold-hardening temperatures of 2 or 4°C for 1, 2, 3, or 4 weeks with soil matric potential of -0.1 or -0.01 MPa. Plants were inoculated with T. ishikariensis after cold-hardening, incubated at 10°C for 25 days in the dark, and then evaluated for regrowth. Overall recovery from snow mold was least when plants were hardened at 2°C for 1 week at -0.01 MPa and greatest when hardened at 4°C for 4 weeks at -0.1 MPa. Survival of plants following snow mold was greater when plants were cold-hardened at 4 than at 2°C and at -0.1 than -0.01 MPa soil matric potential. The greatest difference in survival among lines and correlation with field observations occurred when plants were hardened at 4°C at -0.1 MPa matric potential for 3 weeks. Understanding the influence of temperature and soil matric potential during cold-hardening on speckled snow mold resistance will be useful to breeding programs developing snow-mold-resistant cultivars under controlled environment conditions.