Hybridization using cytoplasmic male sterility and herbicide tolerance from nuclear genes

• US 4,658,084 A
• Filed: 11/14/1985
• Issued: 04/14/1987
• Est. Priority Date: 11/14/1985
• Status: Expired due to Term

• Current Assignee: University of Guelph
• Original Assignee: University of Guelph
• Inventors: Grant, Ian, Beversdorf, Wallace D., Erickson, Lawrence R.
• Primary Examiner(s): Feyrer, James R.
• Application Number:
  US06/797,917
• Time in Patent Office: 516 Days
• Field of Search: 47/58, 47/DIG. 1, 47/1
• US Class Current: 800/266
• CPC Class Codes: A01H 1/023 Male sterility

Abstract

The process of the present invention provides a convenient route for producing a predetermined hybrid variety of a crop which is capable of undergoing both self-pollination and cross-pollination. Cytoplasmic male sterile plants which also exhibit herbicide tolerance attributable solely to nuclear genes are the key plants for use in the present process. Economical bulk planting of the key plants with either maintainer or restorer plants is made possible. Following cross-pollination from a pollen source which lacks the herbicide tolerance unneeded plants effectively are eliminated by use of a herbicide. For instance, unwanted plants may be effectively eliminated immediately after pollination or prior to pollination in the succeeding generation (provided the requisite genes for herbicide tolerance are present therein) to make possible the existence in an unharmed state of a substantially homogeneous stand of the desired plants. In a preferred embodiment cytoplasmic male sterile plants, plants resulting from the self-pollination of a maintainer, and restorer plants are planted in a substantially random population prior to the application of two different herbicides (as defined) at the appropriate times. The process of the present invention is applicable to grain crops, forage crops, seed-propagated fruits, seed-propagated ornamentals, and industrial species. In a particularly preferred embodiment a predetermined variety of Brassica napus (i.e., rape or improved forms thereof known as canola) is formed which is the product of cross-pollination.

Claims

1. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop which is capable of undergoing both self-pollination and cross-pollination comprising:

(a) growing in a first planting area a substantially random population of (1) cytoplasmic male sterile plants which exhibit tolerance to at least one herbicide attributable solely to homozygous dominant nuclear genes, and (2) male fertile plants which are capable of pollinating said cytoplasmic male sterile plants and which lack said herbicide tolerance because the presence of homozygous recessive nuclear genes for such trait, whereby said cytoplasmic male sterile plants (1) and said male fertile plants (2) are pollinated with pollen derived from said male fertile plants and seed is formed on said cytoplasmic male sterile plants and on said male fertile plants,

(b) harvesting in bulk said seed which is formed on said plants of said first planting area,

(c) growing at least a portion of the seed from step (b) in a second planting area in the absence of segregation between the seed derived from said cytoplasmic male sterile plants which exhibit said herbicide tolerance attributable solely to homozygous dominant nuclear genes and said male fertile plants which lack said herbicide tolerance because of the presence of homozygous recessive nuclear genes for such trait, and

(d) contacting prior to pollination substantially all of the plants present in said second planting area with a herbicide which is effective to destroy said plants resulting from seed formed on said male fertile plants of said first planting area, whereby a substantially homogeneous population of a predetermined hybrid variety is formed which resulted from seed formed on said male sterile plants of said first planting area.

2. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said crop is selected from the group consisting of grain crops, forage crops, seed-propagated fruits, seed-propagated ornamentals, and industrial species.

3. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said crop is of the family Brassicaceae.

4. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said crop is of the genus Brassica.

5. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said crop is Brassica napus.

6. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said crop is Brassica campestris.

7. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said male fertile plants (2) are homozygous recessive maintainer plants for said cytoplasmic male sterile plants (1).

8. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said male fertile plants (2) are homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants (1).

9. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said male fertile plants (2) are homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants (1) and said resulting plants of step (d) are male fertile F₁ hybrid plants, and which includes the additional step of:

(e) harvesting seed which forms on said male fertile F₁ hybrid plants as a result of self-pollination.

10. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said male fertile plants (2) are homozygous recessive maintainer plants for said cytoplasmic male sterile plants (1) and said resulting plants of step (d) are cytoplasmic male sterile plants, and which includes the additional steps of:

(e) growing in pollinating proximity to the substantially homogeneous population plants of step (d) a substantially homogeneous population of homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants whereby said cytoplasmic male sterile plants of step (d) are pollinated with pollen from said restorer plants and seed is formed thereon, and

(f) harvesting seed from said cytoplasmic male sterile plants at the conclusion of step (e) which is capable of forming a predetermined male fertile F₁ hybrid variety in the substantial absence of seed from said population of restorer plants.

11. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said pollination takes place with the aid of pollen-carrying insects.

12. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said herbicide is selected from the group consisting of sulfonylureas, glycine derivatives, and imidazolinones.

13. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said herbicide is chlorsulfuron.

14. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 1 wherein said herbicide is glyphosate.

15. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said herbicide is amitrole.

16. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 1 wherein said herbicide is bentazon.

17. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop which is capable of undergoing both self-pollination and cross-pollination comprising:

(a) growing in a planting area a substantially random population of (1) cytoplasmic male sterile plants which exhibit tolerance to at least one herbicide attributable solely to nuclear genes, and (2) male fertile plants which are capable of pollinating said cytoplasmic male sterile plants and which lack said herbicide tolerance because of the absence of the required nuclear genes for such trait, whereby said cytoplasmic male sterile plants (1) are pollinated with pollen derived from said male fertile plants (2),

(b) contacting following said pollination substantially all of the plants present in said planting area with a herbicide which is effective to destroy said male fertile plants and which is ineffective to destroy said cytoplasmic male sterile plants because of said herbicide tolerance attributable solely to said nuclear genes, and

(c) harvesting seed from said cytoplasmic male sterile plants which is capable of forming said hybrid plants in the substantial absence of seed from said male fertile plants which initially grew in said planting area.

18. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said crop is selected from the group consisting of grain crops, forage crops, seed-propagated fruits, seed-propagated ornamentals, and industrial species.

19. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said crop is of the family Brassicaceae.

20. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said crop is of the genus Brassica.

21. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said crop is Brassica napus.

22. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said crop is Brassica campestris.

23. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said male fertile plants (2) are homozygous recessive maintainer plants for said cytoplasmic male sterile plants (1).

24. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said male fertile plants (2) are homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants (1).

25. An improved process for producing seed capable of forming a predetermined variety of hybrid crop according to claim 17 wherein said cytoplasmic male sterile plants (1) possess homozygous dominant nuclear genes for said herbicide tolerance, and said male fertile plants (2) possess homozygous recessive nuclear genes for said herbicide tolerance, and the seed harvested in step (c) additionally is capable of forming hybrid plants which exhibit said herbicide tolerance.

26. An improved process for producing seed capable of forming a predetermined variety of hybrid crop according to claim 17 wherein said cytoplasmic male sterile plants (1) possess homozygous recessive nuclear genes for said herbicide tolerance, and said male fertile plants (2) possess homozygous dominant nuclear genes for said herbicide tolerance, and the seed harvested in step (c) is capable of forming hybrid plants which lack said herbicide tolerance.

27. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said male fertile plants (2) are homozygous recessive maintainer plants for said cytoplasmic male sterile plants (1) and wherein said process includes the additional steps of:

(d) growing as a substantially uniform population at least a portion of said seed from step (c) which is capable of forming plants which are cytoplasmic male sterile plants in pollinating proximity to a substantially uniform population of plants which are a homozygous dominant fertility restorer for said cytoplasmic male sterile plants whereby said cytoplasmic male sterile plants are pollinated with pollen derived from said restorer plants and seed is formed thereon, and

(e) harvesting seed from said cytoplasmic male plants at the conclusion of step (d) which is capable of forming a predetermined male fertile F₁ hybrid variety in the substantial absence of seed from said population of restorer plants.

28. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 17 wherein said cytoplasmic male sterile plants (1) of step (a) possess homozygous dominant nuclear genes for said herbicide tolerance, and said male fertile plants (2) of step (a) are homozygous recessive maintainer plants for said cytoplasmic male sterile plants (1) and possess homozygous recessive nuclear genes for said herbicide tolerance, and wherein said process includes the additional steps of:

(d) growing in a second planting area as a substantially random population at least a portion of the seed from step (c) which is capable of forming plants which are cytoplasmic male sterile and exhibit herbicide tolerance attributable solely to nuclear genes, and plants which are a homozygous dominant fertility restorer for said cytoplasmic male sterile plants and which lack herbicide tolerance because of the presence of homozygous recessive genes for such trait whereby said cytoplasmic male sterile plants are pollinated with pollen derived from said restorer plants,

(e) contacting following said pollination substantially all of the plants present in said second planting area with a herbicide which is effective to destroy said restorer plants because of the lack of said herbicide tolerance and which is ineffective to destroy said cytoplasmic male sterile plants because of the presence of said herbicide tolerance, and

(f) harvesting seed from said cytoplasmic male sterile plants of said second planting area which is capable of forming said hybrid plants in the substantial absence of seed from said restorer plants which initially grew in said second planting area.

29. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said pollination takes place with the aid of pollen-carrying insects.

30. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said herbicide is selected from the group consisting of sulfonylureas, glycine derivatives, and imidazolinones.

31. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said herbicide is chlorsulfuron.

32. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said herbicide is glyphosate.

33. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 17 wherein said herbicide is amitrole.

34. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop to claim 17 wherein said herbicide is bentazon.

35. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop which is capable of undergoing both self-pollination and cross-pollination comprising:

(a) growing in a first planting area a substantially random population of (1) cytoplasmic male sterile plants which exhibit tolerance to a first at least one herbicide which is attributable solely to homozygous nuclear genes and exhibit tolerance to a second at least one herbicide which is attributable solely to different homozygous nuclear genes, and (2) male fertile plants which are homozygous recessive maintainer plants for said cytoplasmic male sterile plants and which lack said herbicide tolerance to said first at least one herbicide because of the absence of the required nuclear genes for such trait and exhibit tolerance to said second at least one herbicide attributable solely to said homozygous nuclear genes, whereby said cytoplasmic male sterile plants (1) and said maintainer plants are pollinated with pollen derived from said maintainer plants and seed is formed on said cytoplasmic male sterile plants and on said maintainer plants,

(b) harvesting in bulk said seed which is formed on said plants of said first planting area,

(c) growing in a second planting area a substantially random population of plants derived from seed harvested in step (b) together with homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants which exhibit herbicide tolerance to said first at least one herbicide attributable solely to said homozygous nuclear genes and lack tolerance to said second at least one herbicide because of the absence of the required nuclear genes for such trait,

(d) contacting prior to pollination substantially all of the plants present in said second planting area with said first herbicide which is effective to destroy said plants resulting from seed formed on said maintainer plants in step (a) whereby cytoplasmic male sterile plants and restorer plants remain,

(e) pollinating said cytoplasmic male sterile plants and said restorer plants of step (d) with pollen derived from said restorer plants and seed is formed on said cytoplasmic male sterile plants and on said restorer plants,

(f) harvesting in bulk the seed which is formed on said plants remaining in said second planting area,

(g) growing in a third planting area a substantially random population of plants derived from seed harvested in step (f), and

(h) contacting substantially all of the plants present in said third planting area with said second herbicide which is effective to destroy said plants resulting from the seed formed on said restorer plants of step (e), whereby a substantially homogeneous population of male fertile F₁ hybrid plants of a predetermined variety is formed.

36. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 35 wherein said crop is selected from the group consisting of grain crops, forage crops, seed-propagated fruits, seed-propagated ornamentals, and industrial species.

37. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein said crop is of the family Brassicaceae.

38. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein said crop is of the genus Brassica.

39. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein said crop is Brassica napus.

40. An improved process for producing a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein said crop is Brassica campestris.

41. An improved process for forming a substantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 35 whrein prior to step (a) the following process steps additionally are practiced:

(i) growing in a preliminary planting area a substantially uniform population of said cytoplasmic male sterile plants in pollinating proximity to a substantially uniform population of different maintainer plants which exhibit tolerance to said first at least one herbicide which is attributable solely to said homozygous nuclear genes and exhibit tolerance to said second at least one herbicide which is attributable solely to said different homozygous nuclear genes whereby said cytoplasmic male sterile plants are pollinated with pollen derived from said different maintainer plants and seed is formed thereon, and

(ii) harvesting seed from said cytoplasmic male sterile plants which subsequently is grown in said first planting area of step (a).

42. An improved process for forming a subtantially homogeneous population of plants of a predetermined hybrid variety of a crop according to claim 35 whrein all of said homozygous nuclear genes for herbicide tolerance are homozygous dominant nuclear genes and said F₁ hybrid plants remaining in step (h) possess herbicide tolerance to said first and said second herbicides.

43. An improved process for forming a substantially homogeneous populaton of plants of a predetermined hybrid variety of crop according to claim 35 which includes the additional step of

(i) harvesting seed which forms on said male fertile F₁ hybrid plants as a result of self-pollination.

44. An improved process for forming a substantially homogeneous populaton of plants of a predetermined hybrid variety of crop according to claim 35 wherein said pollination takes place with the aid of pollen-carrying insects.

45. An improved process for forming a substantially homogeneous population of plants of a predetermined variety of a crop according to claim 35 wherein at least one of said first and said second herbicides is selected from the group consisting of sulfonylureas, glycine derivatives, and imidazolinones.

46. An improved process for forming a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein either said first or said second herbicide is chlorosulforon.

47. An improved process for forming a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein either said first or said second herbicide is glyphosate.

48. An improved process for forming a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein either said first or said second herbicide is amitrole.

49. An improved process for forming a substantially homogeneous population of plants of a predetermined hybrid variety of crop according to claim 35 wherein either said first or said second herbicide is bentazon.

50. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop which is capable of undergoing both self-pollination and cross-pollination comprising:

(a) growing in a planting area a substantially random population of (1) cytoplasmic male sterile plants which exhibit tolerance to a first at least one herbicide which is attributable solely to homozygous nuclear genes, and exhibit tolerance to a second at least one herbicide which is attributable solely to different homozygous nuclear genes, and (2) male fertile plants which are homozygous recessive maintainer plants for said cytoplasmic male sterile plants and which lack said herbicide tolerance to said first at least one herbicide because of the absence of the required nuclear genes for such trait and exhibit tolerance to said second at least one herbicide attributable solely to said homozygous nuclear genes, whereby said cytoplasmic male sterile plants (1) and said maintainer plants are pollinated with pollen derived from said maintainer plants and seed is formed on said cytoplasmic male sterile plants and on said maintainer plants,

(b) harvesting in bulk the seed which is formed on said plants of said first planting area,

(c) growing in a second planting area a substantially random population of plants derived from seed harvested in step (b) together with homozygous dominant fertility restorer plants for said cytoplasmic male sterile plants which exhibit herbicide tolerance to said first at least one herbicide attributable solely to said homozygous nuclear genes and lack tolerance to said second at least one herbicide because of the absence of the required nuclear genes for such trait,

(d) contacting prior to pollination substantially all of the plants present in said second planting area with said first herbicide which is effective to destroy the plants resulting from seed formed on said maintainer plants in step (a) whereby cytoplasmic male sterile plants and restorer plants remain,

(e) pollinating said cytoplasmic male sterile plants and said restorer plants of step (d) with pollen derived from said restorer plants,

(f) subsequently contacting substantially all of the remaining plants present in said second planting area with said second herbicide which is effective to destroy said restorer plants and which is ineffective to destroy cytoplasmic male sterile plants because of said herbicide tolerance attributable solely to said homozygous nuclear genes, and

(g) harvesting seed from said cytoplasmic male sterile plants which is capable of forming F₁ hybrid plants in the substantial absence of seed form said maintainer and restorer plants which initially grew in said seconod planting area.

51. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 50 wherein said crop is selected from the group consisting of grain crops, forage crops, seed-propagated fruits, seed-propagated ornamentals, and industrial species.

52. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein said crop is of the family Brassicaceae.

53. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein said crop is of the genus Brassica.

54. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein said crop is of the genus Brassica napus.

55. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein said crop is of the genus Brassica campestris.

56. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 50 wherein prior to step (a) the following process steps additionally are practiced:

(i) growing in a preliminary planting area a subtantially uniform population of said cytoplasmic male sterile plants in pollinating proximity to a substantially uniform population of different maintainer plants which exhibit tolerance to said first at least one herbicide which is attributable solely to said homozygous nuclear genes and exhibit tolerance to said second at least one herbicide which is attributable solely to said different homozygous nuclear genes whereby said cytoplasmic male sterile plants are pollinated with pollen derived from said different maintainer plants and seed is formed thereon, and

(ii) harvesting seed from said cytoplasmic male sterile plants which subsequently is grown in said first planting area of step (a).

57. An improved process for producing seed capable of forming a predetermined hybrid variety of a crop according to claim 50 wherein all of said homozygous nuclear genes for herbicide tolerance are homozygous dominant nuclear genes and the seed which is harvested in step (g) is capable of forming F₁ hybrid plants which possess herbicide tolerance to said first and said second herbicides.

58. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein said pollination takes place with the aid of pollen-carrying insects.

59. An improved process for producing seed capable of forming a predetermined variety of crop according to claim 50 wherein at least one of said first and said second herbicides is selected from the group consisting of sulfonylureas, glycine derivatives, and imidazolinones.

60. An improved process for prcducing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein either said first or said secord herbicide is chlorosulfuron.

61. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein either said first or said second herbicide is glyphosate.

62. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein either said first or said second herbicide is amitrole.

63. An improved process for producing seed capable of forming a predetermined hybrid variety of crop according to claim 50 wherein either said first or said second herbicide is bentazon.

64. A Brassica napus seed product consisting of a substantially homogeneous assemblage of seeds which upon growth yield rape plants which exhibit a combination of cytoplasmic male sterility and tolerance to at least one herbicide attributable solely to homozygous dominant nuclear genes.

65. A Brassica napus seed product consisting of a substantially homogeneous assemblage of seeds which upon growth yield rape plants which exhibit a combination of cytoplasmic male sterility and tolerance to at least one herbicide attributable solely to homozygous recessive nuclear genes.

66. A Brassica napus seed product consisting of a substantially homogeneous binary admixture of seeds which upon growth yields:

(1) a first rape plant component which exhibits cytoplasmic male sterility and tolerance to at least one herbicide which is attributable solely to homozygous dominant nuclear genes, and

(2) a second rape plant component which is capable of pollinating said first rape plant component, is a homozygous recessive maintainer for said cytoplasmic male sterility of said first rape plant component, and which lacks said herbicide tolerance because of the presence of homozygous recessive nuclear genes for such trait.

67. A Brassica napus seed product consisting of a substantially homogeneous binary admixture of seeds which upon growth yields:

(1) a first rape plant component which exhibits cytoplasmic male sterility and tolerance to at least one herbicide which is attributable solely to homozygous recessive nuclear genes, and

(2) a second rape plant component which is capable of pollinating said first rape plant component, is a homozygous recessive maintainer for said cytoplasmic male sterility of the first rape plant component, and which lacks said herbicide tolerance because of the presence of homozygous dominant nuclear genes for such trait.

68. A Brassica napus seed product consisting of a substantially homogeneous binary admixture of seeds which upon growth yields:

(1) a first rape plant component which exhibits cytoplasmic male sterility and tolerance to at least one herbicide which is attributable solely to homozygous dominant nuclear genes, and

(2) a second rape plant component which is capable of pollinating said first rape plant component, is a homozygous dominant fertility restorer for said first rape plant component, and which lacks said herbicide tolerance because of the presence of homozygous recessive nuclear genes for such trait.

69. A Brassica napus seed product consisting of a substantially homogeneous binary admixture of seeds which upon growth yields:

(1) a first rape plant component which exhibits cytoplasmic male sterility and tolerance to at least one herbicide which is attributable solely to homozygous recessive nuclear genes, and

(2) a second rape plant component which is capable of pollinating said first rape plant component, is a homozygous dominant fertility restorer for said first rape plant component, and which lacks said herbicide tolerance because of the presence of homozygous dominant nuclear genes for such trait.

70. A Brassica napus seed product consisting of a substantially homogeneous assemblage of seeds which upon growth yields male fertile F₁ hybrid rape plants which possess tolerance to at least one herbicide attributable solely to nuclear genes.