Method of producing double low restorer lines of

1. Double low restorer line of Brassica napus for Ogura cytoplasmic male sterility (cms) presenting a Rfo insertion deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea , and having an agronomic value characterized by female fertility, a transmission rate of Rfo and a vegetative vigour, characterized in that said double low restorer line of Brassica napus for Ogura cms presents the five markers PGIol, PGIUNT, PGIint, BolJon and CP418, wherein said markers comprise the following sequences:

PGIol marker: SEQ ID NO:1;

PGIUNT marker: SEQ ID NO:2;

PGIint marker: SEQ ID NO:3;

BolJon marker: SEQ ID NO:4; and

CP418 marker: SEQ ID NO:5.

2. Double low restorer line of Brassica napus according to claim 1 , wherein the BOlJon marker exhibits a radish band, a Brassica oleracea band and a Brassica rapa band in a homozygote of said restorer line.

3. Seeds of Brassica plant developed from the Brassica line of claim 1 wherein the said seeds comprise the Rfo insertion deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea.

4. A method for characterizing recombined restorer lines of Brassica napus for Ogura cms presenting a Rfo insertion deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea , and having an agronomic value characterized by female fertility, transmission rate of Rfo and vegetative vigour; comprising a step wherein the presence of the five markers PGIol, PGIUNT, PGIint, BolJon and CP418 is detected in said recombined restorer lines and wherein said markers comprise the following sequences:

PGIol marker: SEQ ID NO:1;

PGIUNT marker: SEQ ID NO:2;

PGIint marker:SEQ ID NO:3; and

BolJon marker:SEQ ID NO:4,

wherein the marker PGIol is amplified using primers PGIol U, comprising SEQ ID NO:6 and PGIol L, comprising SEQ ID NO:7;

the marker PGIint is amplified using primers PGIint U, comprising SEQ ID NO:8 and PGIint L, comprising SEQ ID NO:9;

the marker BolJon is amplified using primers BolJon U, comprising SEQ ID NO:12 and BolJon L, comprising SEQ ID NO:13; and

the marker PGIUNT is amplified using primers PGIol U comprising SEQ ID NO:6 and PGIint L, comprising SEQ ID NO:9.

5. A method of producing double low restorer lines of Brassica napus for Ogura cytoplasmic male sterility (cms) presenting a radish insertion carrying the Rfo restorer gene deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea , and having an agronomic value characterized by female fertility, transmission rate of Rfo and vegetative vigour, comprising:

a) crossing double low cms lines of spring Brassica napus comprising the deleted radish insertion comprising the Rfo restorer gene, with the double low line of spring Drakkar for forming heterozygous restored plants of Brassica napus;

b) irradiating before meiosis the heterozygous restored plants obtained in step a) with gamma ray irradiation;

c) crossing pollen from flowers obtained in step b) with the cms double low spring Wesroona line;

d) testing the progeny with the five markers PGIol, PGIUNT, PGIint, BolJon and CP418; and

e) selecting the progeny lines presenting the combination of said five markers, and wherein said markers comprise the following sequences:

PGIol marker: SEQ ID NO:1;

PGIUNT marker: SEQ ID NO:2;

PGIint marker:SEQ ID NO:3;

BolJon marker:SEQ ID NO:4; and

CP418 marker: SEQ ID NO:5.

6. The method of claim 5 , wherein said irradiation dose in step b) is 65 Gray during 6 mn.

7. Seeds of a Brassica plant developed from the Brassica line obtained by the method of claim 5 wherein the said seeds comprise the Rfo insertion deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea.

8. Seeds of a Brassica napus obtained by the method of claim 5 deposited in NCIMB Limited, 23 St Machar Drive, Aberdeen, Scotland, AB24 3RY, UK on Jul. 4, 2003, under reference number NCIMB41183.

9. A method of producing Brassica napus hybrid plants, comprising:

a) providing a restorer line produced by the method of claim 5 and bred to be homozygous;

b) using said restorer line in a hybrid production field as the pollinator;

c) using cms sterile plants in a hybrid production field as the hybrid seed producing plant; and

d) harvesting the hybrid seed from the male sterile plant.

10. Seeds of a Brassica napus obtained by the method of claim 9 wherein the said seeds comprise the Rfo insertion deleted of the radish Pgi-2 allele and recombined with the Pgi-2 gene from Brassica oleracea.