Photoperiod-sensitive genie male sterile (PS-GMS) rice has a number of desirable characteristics for hybrid rice production. In this study we made use of a published rice genetic linkage map to determine the locations ofPSGMS genes and we have characterized the effects of these genes on sterility by using molecular markers. A two-step approach was designed for maing the genes: (i) Identifying possible PSGMS gene-containig chromosome regions with bulked DNA from extreme fertile and extreme sterile plants of a very large F2 population and (i) determining the map locations of the genes in extreme sterile individuals. We show that this mapping method is much more cost effective and statistay efficient than using a random sample of an F2 population. We idented two chromosomal regions each containing a PSGMS locus, one designatedpmsl on chromosome 7 and one desinatedpms2 on chromosome 3. The existence of these two loci was confirmed by a large sample assay and with data on ratooning progenies of the F2 plants. A marker-based analysis shows that the effect of pms) is 2-3 times larger than that of pms2 and that dominance is almost complete at both loci. Implications in the breeding of PSGMS rice lines are discussed.A photoperiod-sensitive genic male sterile (PSGMS) rice was found in 1973 as a spontaneous mutant in ajaponica (Oryza sativa ssp. japonica) rice cultivar (Nongken 58) grown in Hubei Province, China (1). Large numbers of studies conducted in the last decade have established that this novel mutant (referred to as Nongken 58S) possesses a number of desirable characteristics that might be useful in hybrid rice (2): pollen fertility of Nongken 58S is regulated by photoperiod length (3); it is completely sterile when grown under long-day conditions, whereas pollen sterility varies when it is grown under short-day conditions; and the critical stage comes between secondary branch differentiation and microsporogenesis during panicle development (4). Thus, PS-GMS rice can be used to propagate itself under short-day conditions and also to produce hybrid seeds by interplanting it with normal fertile lines under long-day conditions. PSGMS rice may therefore provide opportunity to replace the widely used "three-line" (male sterile, maintainer,, and restorer) system with a "two-line" system that promises to greatly reduce costs in labor, time, and resources in hybrid rice production. PSGMS rice has a broad spectrum ofrestoration; almost all normal rice strains restore the fertility of the F1 hybrid. Deliberately bred restorer lines are consequently not required. Fertility is controlled by a relatively simple genetic system, usually one or two major Mendelian loci (1, 5). Thus it should be relatively easy to develop new PSGMS lines by transferring the PSGMS alleles from one genetic background to another, particularly if marker-aided systems of transfer can be developed. A further advantage is that the performance of PSGMS hybrids does not suffer from adverse effects of male sterile cytoplasm such as has commonly been...

This study was conducted to address some of the issues concerning the possible significance of Tibet in the origin and evolution of cultivated barley. A total of 1757 barley accessions from Tibet, including 1496 entries of Hordeum vulgare ssp. vulgare (HV), 229 entries of the six-rowed wild barley H. vulgare ssp. agriocrithon (HA), and 32 entries of the two-rowed wild barley H. vulgare ssp. spontaneum (HS), were assayed for allozymes at four esterase loci. A subsample of 491 accessions was surveyed for spacer-length polymorphism at two ribosomal DNA loci. Genetic variation is extensive in these barley groups, and the amount of genetic diversity in cultivated barley of this region is comparable with that of cultivated barley worldwide. The level of genetic variation of HA is significantly lower than the other two barley groups, and there is also substantial heterogeneity in the level of polymorphism among different agrigeographical subregions. However, little genetic differentiation was detected among the three barley groups (HV, HA, and HS), as well as among different agrigeographical subregions. Comparison of the results from this and previous studies indicated a strong differentiation between Oriental and Occidental barley, thus favoring the hypothesis of a diphyletic origin of cultivated barley.

A random sample of 463 accessions of cultivated barley from the Tibet Hordeum germplasm collection was assayed electorphoretically for genetic diversity at six isozyme loci. Two loci (Acp-1 and Got-1) were found to be monomorphic and extensive variation was detected at the remaining four loci (Est-1, Est-2, Est-3 and Est-4). The allelic composition of Tibetan barley appeared to be distinct as compared to the results of previous studies of barleys from other parts of the world. Partitioning of genetic diversity showed that approximately 96% of the total variation was maintained at the within-subregion level and only about 4% was accounted for by differentiation among the eight subregions. Analysis of multilocus genotypes revealed non-random association of the alleles at the four loci, both in the entire sample and in all the subregions, although the four major multilocus genotypes did not show significant departure from the expectation based on complete random association. The possible causes for the establishment of these multilocus associations were discussed.