Crop Science Journal of Natural Resources and Life Sciences Education
HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
QUICK SEARCH:   [advanced]


     

Published online 1 August 2005
Published in Crop Sci 45:1851-1857 (2005)
© 2005 Crop Science Society of America
677 S. Segoe Rd., Madison, WI 53711 USA
This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Related articles in Crop Science
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (3)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Agricola
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Related Collections
Right arrow Crop Genetics
Right arrow Sunflower

GENOMICS, MOLECULAR GENETICS & BIOTECHNOLOGY

Molecular Mapping of Nuclear Male Sterility Genes in Sunflower

Begoña Pérez-Vicha,*, Simon T. Berryb, Leonardo Velascoa, José M. Fernández-Martíneza, Sonali Gandhic, Carrie Freemanc, Adam Heesackerc, Steven J. Knappd and Alberto J. Leone

a Instituto de Agricultura Sostenible (CSIC), Apartado 4084, E-14080 Córdoba, Spain
b Advanta Seeds UK Ltd., Station Road, Docking, King's Lynn, Norfolk, PE31 8LS, UK
c Dep. of Crop and Soil Science, Oregon State Univ., Corvallis, OR 97331, USA
d Center for Applied Genetic Technologies, 111 Riverbend Road, The Univ. of Georgia, Athens, GA 30602, USA
e Advanta Semillas, Ruta 226, Km 60.0, 7620 Balcarce, Buenos Aires, Argentina

* Corresponding author (bperez{at}cica.es)


   ABSTRACT
TOP
 ABSTRACT
INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
Nuclear male sterility (NMS) is a useful tool for sunflower (Helianthus annuus L.) breeding and genetics programs. A clear understanding of the genetics of NMS at the molecular level and the identification of linked molecular markers will greatly facilitate breeding for this trait. P21 is an inbred line carrying the single gene Ms11 controlling NMS, and NMS801 and NMS373 are two inbred lines with the NMS gene Ms10. The objectives of this study were to (i) identify molecular markers linked with the Ms10 and the Ms11 NMS genes, and (ii) place these genes on the genetic map of sunflower. Three F2 and a BC1F1 mapping populations developed from crosses between the male-sterile (MS) lines P21, NMS801, and NMS373, and male-fertile (MF) (wild-type) lines were scored for fertility/sterility. The NMS801 and NMS373 populations segregated for Ms10 and T, a tightly linked anthocyanin pigment locus. The P21 populations segregated for Ms11. These populations were then genotyped with restriction fragment length polymorphism (RFLP), simple sequence repeat or microsatellite (SSR), and insertion–deletion polymorphism (INDEL) markers, and four genetic maps comprising 14 to 17 linkage groups (LGs) were constructed for each population. The Ms10 and T genes mapped to LG 11, while the Ms11 gene mapped to LG 8. Four SSR markers (ORS697, ORS1214, ORS686, and CRT162) and the phenotypic marker locus T cosegregated and were tightly linked to Ms10 at a genetic distance of less than 1 cM. The Ms11 gene locus was flanked by the SSR markers MS925 and ORS536 at genetic distances of 3.8 and 4.1 cM, respectively. The availability of tightly linked polymerase chain reaction based markers and the location of NMS genes on the sunflower genetic map will be useful for marker-assisted selection (MAS) in sunflower breeding programs and provides a basis for the physical mapping and positional cloning of these genes.

Abbreviations: cM, centimorgan • CMS, cytoplasmic male sterility • INDEL, insertion–deletion polymorphism • INRA, Institut National de la Recherche Agronomique (France) • LG, linkage group • MAS, marker-assisted selection • MF, male-fertile • MS, male-sterile • NMS, nuclear male sterility • RFLP, restriction fragment length polymorphism • SNP, single nucleotide polymorphism • SSCP, single strand conformational polymorphism • SSR, simple sequence repeat or microsatellite


   INTRODUCTION
TOP
 ABSTRACT
 INTRODUCTION
MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 
MALE STERILITY is a condition in plants in which the male gametophytic function is prevented, but the potential for female reproduction remains. On the basis of inheritance patterns, there are two general types of male sterility: NMS and cytoplasmic male sterility (CMS). Both types occur in sunflower. NMS was first discovered by Kuptsov in 1934 (Gundaev, 1971). Since then, several sources of NMS have been reported (Putt, 1966; Vranceanu, 1970; Gundaev, 1971; Jan and Rutger, 1988). The discovery of tight linkage between a NMS gene (Ms10) and an anthocyanin pigment gene (T) by Leclercq (1966) facilitated preanthesis elimination of fertile red plants and made sunflower hybrid production feasible using NMS. Consequently, NMS was used for commercial hybrid seed production in several European countries in the early 1970s. However, the identification of CMS by Leclercq (1969) and the subsequent discovery of fertility restoration genes (Kinman, 1970; Leclercq, 1971; Vranceanu and Stoenescu, 1971) introduced a CMS system and quickly replaced the NMS system for producing hybrid seed.

In contrast to CMS and its commercial use for hybrid production, NMS can improve efficiency of hybridization by eliminating tedious hand emasculation, enhance random mating for population development and recurrent selection, and facilitate the development of testers for inbred line evaluation and selection (Jan, 1992). Nuclear male sterility is usually controlled by single recessive genes, although control by two complementary recessive genes and two genes with epistatic effects have also been described (Miller and Fick, 1997). Allelic relationships among NMS genes have been reported.Vranceanu (1970) tested for allelism among 10 NMS sources isolated from Romanian germplasm and reported the presence of five independent NMS genes, designated Ms1 to Ms5. Jan (1992) evaluated seven induced NMS mutants and two NMS lines, P21 and B11A3, for allelic relationships and demonstrated the existence of six independent genes controlling NMS. The seven NMS mutant lines were placed in four different allelic groups, each representing a unique MS gene, designated Ms6 though Ms9. P21 and B11A3 had different male sterility genes, which also differed from those in the seven mutants. The NMS gene in B11A3 was designated Ms10, and that in P21 Ms11. P21 was released by the USDA and the Texas Agricultural Experiment Station in 1970 as a reselection from their 1968 released P21 ms (Jan, 1992). B11A3 is an inbred line with the NMS gene isolated by Leclercq (1966), which is closely linked to an anthocyanin gene (T) (Stoenescu and Vranceanu, 1977). Allelic relationships between the NMS genes reported by Vranceanu (1970) and Jan (1992) have not been determined.

With the availability of molecular markers and genetic linkage maps in sunflower (Knapp et al., 2001; Tang et al., 2002; Yu et al., 2003), MAS can finally be applied to this important oilseed crop. None of the NMS genes described in sunflower have been genetically mapped. The identification of linked molecular markers could greatly enhance and speed up the transfer of MS alleles to elite inbred lines. Genetic mapping of NMS genes is also a necessary starting point for map-based cloning strategies. The objectives of our research were to (i) identify molecular markers linked to the NMS genes in P21, and NMS lines derived from the INRA (Institut National de la Recherche Agronomique) B11A3 NMS source, and (ii) place the NMS genes on the genetic linkage map of sunflower.


   MATERIALS AND METHODS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
RESULTS
 DISCUSSION
 REFERENCES
 
Plant Materials, Mapping Populations, and Phenotype Evaluation
Four hybrids (NMS801 x 30059, NMS373 x ANN1811, P21 x P-96, P21 x K-96) were produced by crossing MS individuals (ms10ms10 or ms11ms11) from NMS lines (NMS801, NMS373, and P21) to nuclear MF individuals (Ms10Ms10 or Ms11Ms11) from four wild-type lines (Jan, 1992; Miller, 1992, 1997; Fernández-Martínez et al., 2004). NMS801 x 30059 and NMS373 x ANN1811 segregated for Ms10 and T, a tightly linked anthocyanin pigment locus, whereas P21 x P-96 and P21 x K-96 segregated for Ms11. T is linked in coupling to Ms10; for example, MS plants are ms10t/ms10t. NMS801 and NMS373 are BC5F4–derived sib-mated populations resulting from crosses between unpigmented (green) nuclear MS plants and anthocyanin-pigmented MF plants (Miller, 1992, 1997). The original source for ms10 and t in NMS373 and NMS801 was the inbred line INRA B11A3 (Miller, 1992, 1997). P21 was released by the USDA and the Texas Agricultural Experiment Station in 1970 as a reselection from their 1968 released P21 ms (Jan, 1992) and is the original source for ms11. The NMS lines have been maintained by sib-mating MS to MF individuals, for example, Ms11ms11 x ms11ms11. The wild-type parents were an elite proprietary inbred line (30059), two broomrape (Orobanche cumana Wallr.) resistant inbred lines (P-96 and K-96; Fernández-Martínez et al., 2004), and a wild H. annuus population (ANN1811; PI 494567).

Genetic maps were constructed by genotyping 94 F2 progeny from NMS801 x 30059 (Berry, 1995), 212 BC1F1 progeny from NMS373 x ANN1811 (Gandhi et al., 2005), 113 F2 progeny from P21 x P-96 (Pérez-Vich et al., 2004), and 182 F2 progeny from P21 x K-96 (Table 1). Nuclear male sterility lines were used as females in all the crosses. F2 progenies were obtained by selfing individual F1 plants. BC1F1 progenies were obtained by backcrossing a single hybrid plant (NMS373 x ANN1811) to a MS plant (NMS373). The F2 and BC1F1 plants were visually evaluated for male sterility at flowering time in the following environmental conditions: (i) F2 NMS801 x 30059: Greenhouse at Balcarce (Argentina) in winter 1993, (ii) F2 P21 x P-96: Field at the experimental farm of the Institute for Sustainable Agriculture at Córdoba (Spain) in spring 2000 (iii) F2 P21 x K-96: Field at the experimental farm of the Institute for Sustainable Agriculture at Córdoba (Spain) in spring 2001, and (iv) BC1F1 NMS373 x ANN1811: Field at Corvallis, OR, in summer 2002. Plants with full anther extrusion and pollen production were classified as MF, and plants lacking anther extrusion and pollen grains were classified as MS. The NMS373 x ANN1811 BC1F1 population was also phenotyped for hypocotyl and leaf petiole color. Plants were classified as anthocyanin-pigmented (red) or unpigmented (green).


View this table:
[in this window]
[in a new window]
  		Table 1. The number of individuals, genetic map characteristics, and nuclear male sterility (NMS) phenotypic segregation in each of the F2 mapping populations.{dagger}

 
Molecular Marker Assays
Three fully expanded leaves were cut from each of the F2 or BC1F1 plants from the mapping populations and frozen at –80°C. The leaf tissue was lyophilized and ground to a fine powder in a laboratory mill. DNA was isolated as described in Yu et al. (2003) and Pérez-Vich et al. (2004). Different types of molecular markers were assayed in each population (Table 1). The RFLPs and SSRs were assayed in the NMS801 x 30059 and the P21 x P-96 populations, SSRs and INDELs in the P21 x K-96 population, and SSRs, INDELs, single nucleotide polymorphisms (SNPs), and SSCPs (single-strand conformational polymorphisms) in the NMS373 x ANN1811 population. The RFLP marker analysis was performed as described by Berry et al. (1995), using the RFLP probes developed and mapped by Berry et al. (1994)(1995, 1996). The RFLP marker loci were identified by ZVG prefixes. The SSR genotyping assays in the NMS373 x ANN1811 population were performed as described by Tang et al. (2002) on an ABI Prism 377 DNA Sequencer (Applied Biosystems, Foster City, CA) by means of polyacrylamide gels and fluorescent labeled amplicons. The SSR assays in the P21 x P-96 and the P21 x K-96 populations were performed as described by Pérez-Vich et al. (2004). The SSR primers from several sources were used, and they are identified by the prefixes MS (Paniego et al., 2002), ORS (Tang et al., 2002), and CRT (Yu et al., 2003). The INDEL markers for previously mapped RFLP markers (Berry et al., 1997), identified also by ZVG prefixes, were genotyped as described by Yu et al. (2003). The SSCP genotyping was performed as described by Gandhi et al. (2005).

Linkage Map Construction, Map Merging, and Gene Mapping of the Ms10, Ms11, and T Genes
Chi-square analyses were performed on each locus to detect deviations from the expected Mendelian ratios for codominant (1:2:1) or dominant (3:1) markers. Linkage maps were constructed using the software MAPMAKER/EXP version 3.0b (Whitehead Institute, Cambridge, MA) (Lander et al., 1987). Two-point analysis was used to identify LGs at a minimum LOD score of 2.5 and a maximum recombination frequency of 0.40. Three-point and multipoint analyses were used to determine the order and interval distances between the markers in each LG. The Kosambi mapping function was used to compute the map distances in centimorgans (cM) from the recombination fractions. The LG nomenclature follows Berry et al. (1997) and Tang et al. (2002). A consensus map was made for the P21 x P-96 and the P21 x K-96 crosses using the common markers as anchor loci (i.e., a common data file for both populations was constructed in which markers segregating in only one population were coded as missing data in the other one). Linkage group maps were drawn using the MapChart software (Voorrips, 2002). The genotypes for the Ms10 and Ms11 genes were inferred from male fertility phenotypes in the F2 and BC1F1 plants, and mapped accordingly with a LOD threshold of 3.0. Male-fertile F2 plants were scored as Ms10_ or Ms11_, whereas MS F2 plants were scored as ms10ms10 or ms11ms11. In the BC1F1, MF plants were scored as Ms10ms10, and MS plants as ms10ms10, while anthocyanin-pigmented (red) plants were scored as Tt, and green plants as tt.


   RESULTS
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
DISCUSSION
 REFERENCES
 
NMS801 x 30059 Population
The NMS801 x 30059 F2 population segregated in a 3:1 ratio of MF to MS plants (Table 1), indicating segregation of the single gene Ms10. For mapping Ms10, 95 RFLP probes covering the 17 LGs of sunflower were chosen and screened for polymorphisms between NMS801 and 30059 digested with either EcoRI or EcoRV. Fifty-eight (61%) of the probes detected a polymorphism between the parental lines. These polymorphic RFLP marker loci were genotyped in the F2 and a genetic map including Ms10 was constructed to identify the LG containing this gene. Ms10 mapped to LG 11. Once LG 11 was identified, all the RFLP probes previously mapped to this LG were screened for polymorphisms between the parents (DNAs were digested with EcoRI, EcoRV, HindIII, and DraI). Five additional polymorphic markers were identified, which were genotyped in the F2 and mapped to LG 11. The Ms10 locus was flanked by the marker loci ZVG1039 and ZVG52 (Fig. 1). The distance separating Ms10 and the closest marker locus (ZVG52) was 5 cM (Fig. 1). The map of LG 11 contained 10 RFLP loci (Fig. 1), five of which (ZVG49, ZVG50, ZVG51, ZVG52, and ZVG53) have been integrated in public maps (Tang et al., 2002; Yu et al., 2003).



View larger version (28K):
[in this window]
[in a new window]
  		Fig. 1. Molecular maps of the sunflower linkage group (LG) 11 containing the Ms10 gene for nuclear male sterility. Two individual maps were obtained from the NMS801 x 30059 (left) and the NMS373 x ANN1811 (right) populations. The ORS prefix denotes public simple sequence repeat or microsatellite (SSR) marker loci, the ZVG prefix denotes restriction fragment length polymorphism or insertion–deletion polymorphism marker loci, and the CRT denotes CARTISOL SSR marker loci. Common markers which segregated in both populations are underlined and related with lines. The cumulative distances in centimorgans are shown at the left of each map. Resolution of both maps is not enough to determine the distance and locus order in the Ms10–T cluster.

 
NMS373 x ANN1811 Population
The NMS373 x ANN1811 map was constructed by genotyping 132 SSR, INDEL, SNP, or SSCP marker loci on 212 BC1 progeny (Gandhi et al., 2005). Loci merged into 17 LGs, and spanned the sunflower genome, as demarcated by loci on reference maps. Groups and locus orders were identical for common DNA markers appearing on NMS373 x ANN1811 and previously published maps (Gandhi et al., 2005).

Genotypes for Ms10 and T were inferred from male-sterility and anthocyanin pigment phenotypes, respectively, among NMS373 and ANN1811 individuals and NMS373 x [NMS373 x ANN1811] BC1 progeny. ANN1811 individuals were MF and presumably homozygous for wild-type alleles (Ms10Ms10). NMS373 sibs (which are obtained through the cross ms10ms10 x Ms10ms10 and therefore show a segregation for Ms10 similar to that in a BC1F1) segregated 96:1:0:103 MF, pigmented (Ms10ms10Tt)/MF, unpigmented (Ms10ms10tt)/MS, pigmented (ms10ms10Tt)/MS, unpigmented (ms10ms10tt). The observed segregation ratios for Ms10 (97:103 MF/MS) and T (96:104 pigmented/unpigmented) were not significantly different from 1:1 ({chi}2 = 0.18, P = 0.67 for Ms10; {chi}2 = 0.32, P = 0.57 for T). The recombination frequency between Ms10 and T was 0.005 (one recombinant was observed among 200 NMS373 individuals).

Unexpectedly, Ms10 did not segregate among NMS373 x [NMS373 x ANN1811] BC1 progeny as none of the individuals was MS. We suspect that the original hybrid (NMS373/ANN1811) was homozygous MF (Ms10Ms10), not heterozygous MF (Ms10ms10). The observed segregation ratio for T in the BC1 (110:104 pigmented/nonpigmented) was not significantly different from 1:1 ({chi}2 = 0.17, P = 0.68). T mapped to LG 11 and cosegregated with four SSR marker loci (ORS686, ORS697, ORS1214, and CRT162) (Fig. 1).

The NMS373 x ANN1811 and NMS801 x 30059 linkage maps for LG 11 shared two DNA marker loci, ZVG49 and ZVG51 (Fig. 1), and both of these mapped to one side of Ms10. Tight linkage between Ms10 and T supplied a third interconnection between the two maps; however, because Ms10 did not segregate in NMS373 x ANN1811, the orientation of T and Ms10 on LG 11 is not known. Male-fertile (Ms10ms10) and MS (ms10ms10) NMS373 individuals were screened for polymorphisms among every previously mapped SSR and INDEL markers in a 30-cM window of Ms10 on LG 11 (Tang et al., 2002; Yu et al., 2003; S.J. Knapp, 2003, unpublished data) and none were polymorphic.

P21 x P-96 Population
The P21 x P-96 F2 population segregated following a 3:1 ratio of MF to MS plants (Table 1), indicating segregation of a single, recessive gene (Ms11). The P21 x P-96 map construction has been described in Pérez-Vich et al. (2004). This original map, which comprised 103 marker loci (77 RFLPs + 26 SSRs) arranged in 17 LGs and spanning a distance of 1144.4 cM, was used to identify the LG containing the Ms11 gene. This gene was found to map to LG 8, which contained three RFLP and four proprietary SSR marker loci (Pérez-Vich et al., 2004). For the present study, the parents of the mapping population (P21 and P-96) were screened for polymorphisms with a set of 22 SSRs from LG 8 (Tang et al., 2002, 2003) for the purpose of positioning Ms11 in relation to public SSR markers. Four additional SSR markers (ORS243, ORS780, ORS898, and ORS1161) that revealed codominant marker loci were mapped to LG 8, which now comprised three RFLP + four proprietary SSR + four public SSR-marker loci. Linkage Group 8 was 60.9 cM long, with an average marker interval of 5.5 cM (Fig. 2). The locus order for the public SSR markers and the reference linkage maps (Tang et al., 2002, 2003) was identical. The Ms11 gene mapped 34.2 cM downstream from the upper end of LG 8, between the SSR proprietary marker MS677 and the public SSR marker ORS243 (Fig. 2). The MS677 and the ORS243 markers were 4.5 cM distal and 5.1 cM proximal, respectively, of the Ms11 locus (Fig. 2).



View larger version (37K):
[in this window]
[in a new window]
  		Fig. 2. Molecular maps of the sunflower Linkage Group 8 containing the Ms11 gene for nuclear male sterility. Two individual maps were first obtained from the P21 x P-96 (left) and the P21 x K-96 (right) populations. A consensus map was constructed with MAPMAKER/EXP using segregation data from the two populations. Common markers which segregated in both populations are underlined and related with lines. The ORS prefix denotes public simple sequence repeat or microsatellite (SSR) marker loci, the MS prefix denotes proprietary SSR marker loci, and the ZVG prefix denotes restriction fragment length polymorphism or insertion–deletion polymorphism marker loci. The cumulative distances in centimorgans are shown at the left of each map.

 
P21 x K-96 Population
Segregation of MF to MS plants in the F2 progeny of the P21 x K-96 cross fit a 3:1 MF/MS ratio, indicating a single recessive gene (Ms11) determining NMS (Table 1). The P21 x K-96 map comprised 67 marker loci (62 SSRs + 5 INDELs) arranged in 14 LGs and spanning a distance of 731 cM (Pérez-Vich and Leon, 2003, unpublished data). The Ms11 gene was again found to map to LG 8. Following the same approach as described above for the P21 x P-96 population, additional public SSR markers on LG 8 (Tang et al., 2002, 2003) were screened for polymorphisms between the parental lines P21 and K-96. Four polymorphic SSR markers (ORS243, ORS536, ORS780, and ORS894) were identified and mapped to LG 8. Therefore, in the P21 x K-96 population, LG 8 was assembled using four proprietary and four public SSR-marker loci, spanning a distance of 72.5 cM (Fig. 2). The locus orders for public SSR markers were identical between P21 x K-96 and reference maps (Tang et al., 2002, 2003). Ms11 mapped between the proprietary SSR marker MS925 and the public SSR marker ORS536, at distances of 4.2 and 4.4 cM, respectively (Fig. 2).

The P21 x P-96 and P21 x K-96 maps shared four SSR markers on LG 8 (MS571, MS677, ORS243, and ORS780), which allowed the construction of a composite map. The integrated map contained 16 marker loci and spanned 68.5 cM (Fig. 2). Ms11 mapped to a similar position in consensus and individual maps (Fig. 2). The nearest public SSR marker (ORS536) mapped 4.1 cM proximal to Ms11 (Fig. 2).


   DISCUSSION
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
REFERENCES
 
With four genetic maps, the Ms10 and the T genes were mapped to LG 11, while the Ms11 gene was mapped to LG 8. The genes mapped to intermediate regions of these LGs and were flanked by molecular markers. Male-sterile genes have been mapped in other crops, such as soybean [Glycine max (L.) Merr.] (Jin et al., 1998), rice (Oryza sativa L.) (Wang et al., 1995, 2003; Yamagushi et al., 1997; Subudhi et al., 1997; Koh et al., 1999; Dong et al., 2000), or wheat (Triticum aestivum L.) (Xing et al., 2003); however, this is the first report on the molecular mapping of NMS genes in sunflower. Burke et al. (2002) mapped a dominant morphological marker for hypocotyl and disk pigmentation to LG 11 and named the locus "pigment." The pigment locus mapped between the SSR markers ORS5 and ORS210, in the segment spanned by ORS733 and ORS607. However, we have not data enough to determine if the pigment locus of Burke et al. (2002) is the T gene mapped in this study.

The genetic relationships between all the published sunflower NMS genes have not yet been elucidated. Vranceanu (1970) described the existence of five different NMS genes (Ms1 to Ms5) on 10 NMS sources isolated from Romanian sunflower, and Jan (1992) reported six independent recessive genes (Ms6 to Ms11) on nine NMS sources (seven NMS mutants and the NMS lines P21 and B11A3). Segregation studies of crosses between the P21 and the B11A3 lines indicated that Ms10 and Ms11 were not genetically linked (Jan, 1992), which has been demonstrated in the present study using a molecular approach. Allelic relationships between the five NMS genes reported by Vranceanu (1970) and the six NMS genes reported by Jan (1992) have not been determined. The number of allelism tests required to differentiate these genes grows rapidly as additional NMS sources are described. Using the results of this study as a starting point, mapping other NMS genes on the sunflower linkage map is probably the quickest method of differentiating the various NMS genes. Allelism tests can then be performed on genes that map to similar locations.

The major use of NMS in sunflower breeding is in the development of testers for inbred line evaluation. This requires the introgression of the NMS genes into several testers for each breeding program. Since sunflower NMS is controlled by single recessive genes, the presence of the MS allele in backcrossed lines (heterozygotes) can only be detected by progeny testing. Currently, breeders use self pollination alternating with backcrossing to identify lines carrying the MS allele. In addition, recessive NMS must be propagated via the heterozygotes (Msms). Therefore, the yield of MS progeny is limited to 50% in a backcross to msms, and 25% in an F2 generation. DNA markers linked to NMS loci provide a useful approach for early and accurate identification of lines carrying the MS allele, without the need of progeny testing.

Several molecular markers have been identified for MAS of Ms10 and Ms11. The two SSR markers MS925 and ORS536 flank Ms11 at genetic distances of 3.8 and 4.1 cM, respectively. These markers are codominant and can therefore be used to identify and select ms11ms11 homozygotes or Ms11ms11 heterozygotes for genetic male-sterility loci. The fact that the markers flank the gene makes them more reliable than a single marker. Additionally, several other SSR markers reside in the LG 8 segment spanned by MS925 and ORS243 (Tang et al., 2002; Yu et al., 2003). These markers were monomorphic in the populations used in this study, but could be polymorphic in other populations and more tightly linked to Ms11 than MS925 and ORS243.

The Ms10–T gene cluster cosegregated with several SSR marker loci. No recombination was observed between ORS697, ORS1214, CRT162, ORS686, and T among 212 progeny tested. If the next individual tested were a recombinant, then the recombination value would be 1/213 or 0.0047. Therefore, these markers must be less than 0.475 cM from T. Tight linkage between T and Ms10 (<1 cM) was also previously reported by Leclercq (1966) and Stoenescu and Vranceanu (1977). In this study, however, none of the phenotypic or DNA markers were mapped to the resolution needed to ascertain the order and orientation of loci in the Ms10–T cluster. The SSR codominant markers closely linked to Ms10–T may be useful for MAS and can be used alone or in concert with T, which is a highly reliable phenotypic marker.

Pollen development in higher plants is a complex process (McCormick, 1993). In sunflower, besides gross descriptions, detailed cytological descriptions of the NMS lines have been very limited (Jan, 1997). The fact that at least six independent genes controlling NMS have been reported (Jan, 1992), including the two mapped in this study and located on different LGs, substantiates the complexity involved in the manifestation of this phenotype. For a better understanding of the molecular biology of NMS in sunflower, the ultimate goal would be to clone and characterize the function of a number of different NMS genes. Map-based cloning requires that the target gene has a clear phenotype and that its position on the genetic map is known. The placement of Ms10 and Ms11 on the sunflower genetic map, and the identification of molecular markers closely linked to these genes are the first steps in this process.


   ACKNOWLEDGMENTS
 
This work was supported by a postdoctoral contract to B. Pérez-Vich from the Spanish Ramón y Cajal program (MEC-FEDER), and funded by Advanta Seeds, by grants to J.M. Fernández-Martínez from the Spanish National Institute for Agricultural Research (INIA) (#RTA01-131), and by grants to S.J. Knapp from the United States Department of Agriculture (USDA) National Research Initiative Competitive Grants Program Plant Genome Program (#98-35300-6166) and the USDA Cooperative State Research Education and Extension Service Initiative for Future Agricultural and Food Systems Plant Genome Program (#2000-04292).

Received for publication November 29, 2004.


   REFERENCES
TOP
 ABSTRACT
 INTRODUCTION
 MATERIALS AND METHODS
 RESULTS
 DISCUSSION
 REFERENCES
 


Related articles in Crop Science:

THIS ISSUE IN CROP SCIENCE

Crop Science 2005 45: x. [Full Text]  




This Article
Right arrow Abstract Freely available
Right arrow Figures Only
Right arrow Full Text (PDF) Free
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Related articles in Crop Science
Right arrow Similar articles in this journal
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via ISI Web of Science (3)
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Right arrow Search for Related Content
PubMed
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Agricola
Right arrow Articles by Pérez-Vich, B.
Right arrow Articles by Leon, A. J.
Related Collections
Right arrow Crop Genetics
Right arrow Sunflower

HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS
The SCI Journals Agronomy Journal Vadose Zone Journal
Journal of Natural Resources
and Life Sciences Education		 Soil Science Society of America Journal
Journal of Plant Registrations Journal of
Environmental Quality		 The Plant Genome