Search

The use of thermosensitive genetic male sterility (TGMS) in the development and production of rice (Oryza sativaL.) hybrids is an alternative to the cytoplasmic‐genetic male sterility (CMS) system. This study aimed to develop TGMS lines with aromatic Thai rice background by molecular marker‐aided breeding. Four microsatellite markers (RM2, RM10, RM11, and RM214) on chromosome 7 in the vicinity of the TGMS gene tms2and showing polymorphism between the two parents were used in genotyping the mapping population consisting of 157 F2plants derived from a cross between Norin PL12 (a TGMS line from Japan) and KDML 105 (a popular aromatic Thai rice cultivar). The RM11 marker was approximately 5 centimorgans (cM) from tms2while RM2 was approximately 16 cM from it. In this F2population, the accuracy of selecting sterile plants with RM2 and RM11 markers was 92 and 97%, respectively. In three backcrosses, the accuracy of selection with markers for either homozygous or heterozygous plants was higher than 90% with RM2. Using RM11, we obtained 89% accuracy for selecting homozygous fertile plants and 59% accuracy for selecting heterozygous plants. The results demonstrated that microsatellite markers were powerful in screening large breeding populations, and these markers facilitated selection for plants possessing the tms2in an early stage of the crop and without exposing the materials to the required temperature for TGMS gene expression. Three TGMS lines with aromatic Thai rice background were developed and showed complete pollen sterility when maximum temperature was higher than 30°C, 1 to 2 wk after panicle initiation. Up to 77% spikelet fertility was observed when these lines were exposed at temperature below 30°C during the critical stage.

Speed, efficiency, and safety considerations have led many genome mapping projects to evaluate polymerase chain reaction (PCR) sequence amplification as an alternative to Southern blot analysis. However, the availability of informative primer sequences can be a limiting factor in PCR-based mapping. An alternative to random amplified polymorphism detection (RAPD) is the sequence-tagged-site (STS) approach. If informative primer sequences could be derived from known sequences, then current maps, which are based on both known function and anonymous clones, might be easily converted to maps utilizing PCR technology. In this paper, four pairs of primer sequences were obtained from published sequences, and four pairs were obtained by sequencing portions of DNA clones from genomic clones derived from a random genomic library used in the North American Barley Genome Mapping Project (NABGMP). These primers were used to screen for polymorphisms in the progeny of a winter x spring and a spring x spring barley cross. Two types of polymorphisms were distinguished using these primer sets: (1) insertion/deletion events that could be read directly from agarose gels, and (2) point mutation events. The latter were identified using polyacrylamide-gel electrophoresis of PCR products following digestion with restriction endonucleases (four-base cutters). To determine whether the PCR-based polymorphisms were allelic to polymorphisms identified by the clones from which the primer sequences derived, chromosomal assignments and (when possible) co-segregation analysis was performed.