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...

Cotton, the leading natural fiber crop, is largely produced by two primary cultivated allotetraploid species known as Upland or American cotton ( Gossypium hirsutum L.) and Pima or Egyptian cotton ( G. barbadense L.). The allotetraploid species diverged from each other and from their diploid progenitors (A or D genome) through selection and domestication after polyploidization. To analyze cotton AD genomes and dissect agronomic traits, we have developed a genetic map in an F2 population derived from interspecific hybrids between G. hirsutum L. cv. Acala-44 and G. barbadense L. cv. Pima S-7. A total of 392 genetic loci, including 333 amplified fragment length polymorphisms (AFLPs), 47 simple sequence repeats (SSRs), and 12 restriction fragment length polymorphisms (RFLPs), were mapped in 42 linkage groups, which span 3,287 cM and cover approximately 70% of the genome. Using chromosomal aneuploid interspecific hybrids and a set of 29 RFLP and SSR framework markers, we assigned 19 linkage groups involving 223 loci to 12 chromosomes. Comparing four pairs of homoeologous chromosomes, we found that with one exception linkage distances in the A-subgenome chromosomes were larger than those in their D-subgenome homoeologues, reflecting higher recombination frequencies and/or larger chromosomes in the A subgenome. Segregation distortion was observed in 30 out of 392 loci mapped in cotton. Moreover, approximately 29% of the RFLPs behaved as dominant loci, which may result from rapid genomic changes. The cotton genetic map was used for quantitative trait loci (QTL) analysis using composite interval mapping and permutation tests. We detected seven QTLs for six fiber-related traits; five of these were distributed among A-subgenome chromosomes, the genome donor of fiber traits. The detection of QTLs in both the A subgenome in this study and the D subgenome in a previous study suggests that fiber-related traits are controlled by the genes in homoeologous genomes, which are subjected to selection and domestication. Some chromosomes contain clusters of QTLs and presumably contribute to the large amount of phenotypic variation that is present for fiber-related traits.

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ABSTRACTof two-line hybrids has thus become a major goal in many rice breeding programs in China and has led to Photoperiod-sensitive genic male sterility (PSGMS) rice has a numthe release of several hybrids that have started to gain ber of desirable characteristics for hybrid rice production. In this study, we conducted a molecular marker-based mapping and genetic large acreage in rice production. analysis of PSGMS genes using two crosses involving the originalThere has been a large number of inheritance studies

Photoperiod-sensitive genic male sterile (PSGMS) rice is a very useful germplasm for hybrid rice development. It was first found as a spontaneous mutant in a japonica cultivar 'Nongken 58.pms3 on chromosome 12 was determined to be the locus where the original PSGMS mutation occurred, changing the normal cultivar Nongken 58 to PS-GMS Nongken 58S. Large amounts of RAPD and AFLP analyses were also conducted for the fine mapping of the pms3 genomic region, which resulted in 4 molecular markers linked to pms3. Although these markers somewhat increased the marker density of this region, the pms3 locus is still located in a marker-sparse region.