Classifications

• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
  • A01H1/00—Processes for modifying genotypes ; Plants characterised by associated natural traits
  • A01H1/04—Processes of selection involving genotypic or phenotypic markers; Methods of using phenotypic markers for selection
• • A—HUMAN NECESSITIES
  • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
  • A01H—NEW PLANTS OR NON-TRANSGENIC PROCESSES FOR OBTAINING THEM; PLANT REPRODUCTION BY TISSUE CULTURE TECHNIQUES
  • A01H1/00—Processes for modifying genotypes ; Plants characterised by associated natural traits
  • A01H1/02—Methods or apparatus for hybridisation; Artificial pollination ; Fertility
  • A01H1/022—Genic fertility modification, e.g. apomixis
  • A01H1/023—Male sterility

Definitions

• This invention relates to the production of hybrids of cereal crops, particularly, but not exclusively, small grained cereals such as wheat and barley.
• the invention concerns new genetically transformed plants, for use with this method.
• the traditional manner of producing hybrid plants involves manual emasculation of the female parent, so that self-pollination is not posible, which is planted proximate the fertile male parent. This procedure is only practical when it is possible to remove the pollen bearing structures from the female parent. In many species, however, the flowers are so insignificant in size that manual emasculation of the female parent of an intended cross is simply impracticable. This is particularly so with small-grained cereals such as wheat, barley, rice and grass species.
• sterility may be induced by treatment of the plant with a chemical hybridising agent (CHA) which inhibits synthesis of viable pollen.
• CHA treatment is somehwat inefficient and a certain amount of self-pollination occurs which results in the harvested hybrid seed containing some seed of the female parent.
• the male parent is normally grown in clearly indentifiable rows or blocks and are simply not harvested; the male parents thus present no problem to hybrid purity.
• the seed hybrids which are produced using CHAs tend to be contaminated with seed of the female parent and separation of this rogue contaminant is virtually impossible.
• CMS cytoplasmic male sterility
• the Z and X lines are crossed to produce the Y line, Then the Y line is crossed with the Z line giving progeny of which 80% are of the Z line genotype and 20% of the Y-type genotype. This mixed population is then used in a cross with any desirable male fertile line to produce the commercial FI hybrids.
• the principal advantage of the XYZ system is that the alien restorer chromosome is eliminated by physical separation and does not apper in the commercial hybrid.
• chromosome 5R of a gene restorer chromosome was the presence on 5R of a gene producing a hairy peduncle (Hp) which allows identification of any plants carrying the alien restorer chromosome to be identified visually.
• Hp hairy peduncle
• Driscoll subsequently proposed a modified XYZ system for wheat ["Modified XYZ System of Producing Hybrid Wheat” Crop Science 25, 1115-1116 (1985)].
• the alien chromosome was to be an isochromosome.
• this modification is not of any particular relevance.
• An object of the present invention is to obviate or mitigate the aforesaid disadvantages.
• Figure 1 shows the scheme of the Driscoll XYZ system, as discussed previously.
• Figure 2 shows an aspect of the system of the present invention using an addition plant line.
• Figure 3 shows another aspect of the system of the present invention using a substitution line and a 3-way cross system.
• Figure 4 shows another aspect of the system of the present invention using a substitution line and a single cross.
• a ccording to the present invention there is provided a method for the maintenance of a male sterile parental plant line for use in the production of hybrids, comprising crossing a homozygous male sterile plant, representing the female parent, with a male parent which is isogenic to the female but having a chromosome bearing a dominant male fertility gene and a marker gene which confers a characteristic colouration on the progeny seed, harvesting from that cross a population of progeny seed consisting of a mixture of the two parental lines, and physically separating the pro.geny seed on the basis of the colour marker.
• the chromosome bearing the dominant male fertility gene may be an additional gene, so that for example, in wheat the female has 43 chromosomes, or else may be a substitution, whereby the female has the usual number of chromosomes; for example, 42 for wheat.
• Separation of the mixed population of progeny seed may therefore be effected using commercially available seed-sorting machinery which is capable of colour discrimination.
• the present invention is particularly applicable to the production of hybrid wheat and barley.
• the method of the invention may be applied to any plant species for which the appropriate starting materials exist or may be created.
• Other such species include rice, maize and grass species.
• the colour marker be the blue aleurone marker gene available on chromosome 4 of A ⁇ ropyron elonoatum (4Ag) .
• the male parent used in this invention is suitably a translocation of 4Ag to the restorer arm of chromosome 4 of Triticum thaoudar (4th) and chromosome 4 of Tricicum monococcum (4m), both of which are diploid wheats or to the restorer arm of chromosome 4 of Triticum urartu.
• the present invention may be viewed as a modification of the XYZ system of Driscoll. Driscoll's proposal to use rye chromosome 5R effectively limited the size of the Z populations. This is because of the need for intense roguing to remove plants carrying the hairy peduncle: similar roguing would be necessary in the commercial production phase.
• the present invention utilises a distinctive colour marker such as the blue aleurone gene from A ⁇ ropyron elon ⁇ atum L. (4Ag) .
• a distinctive colour marker such as the blue aleurone gene from A ⁇ ropyron elon ⁇ atum L. (4Ag) .
• 4Ag chromosome 4Ag substitutions were vigorous but male sterile. This indicates that 4Ag lacks the gene for male fertility restoration, necessary to restore the Z line in Driscoll*s XYZ system, which has been confirmed in recent tests.
• Triticum monococcum (4m) , Triticum thaoudar (4th) or Triticum urartu (4u) have been located and have been found to carry both the blue aleurone marker (BL) and a male fertility restorer (+MS) .
• Crossing of the translocation into a male sterile line provides a suitable material for use in the present invention.
• substitution line propagation of the addition plant lines can give rise to a substitution line, particularly after self-pollination for several generations.
• the substitution possibly occurs by centric fusion or Robertsonian translocation, for example, by the substitution of one arm from a A ⁇ ropyron elon ⁇ atum L. chromosome with one arm from T. monococcum or T. thaoudar.
• the substitution plant line has some further advantages in comparison to the addition line.
• the nuc -r male sterile (NMS) system is based on an addition line (43 chromosomes, while bread wheat normally carries 42 chromosomes) .
• an addition line may have some disadvantages particularly with seed production.
• an addition line in which the 43rd chromosome carries the blue aleurone marker(s) and the male fertility restorer
• self-pollinates the progeny will be approximately 72% non-blue and male sterile.
• a substitution line consists of the normal 42 chromosome complement of bread wheat, for example, in which a wheat chromosome is replaced by a non-bread wheat chromosome. This means that the segregation ratio will approximate the Mendelian ration of 3:1, and so approximately 75% will be blue, and 25% non-blue.
• a nuclear male sterile line of variety PROBUS was backcrossed into a variety of cultivars to introduce the male sterile recessive genotype thereto. This provided a series of lines constituting the Z line for use in the breeding scheme of this invention.
• the cultivars were: HARRIER, SUNECA, VASCO, TORRES, SUNSTAR, BANKS, SKUA, AROONA, VULCAN AND TORDO.
• the Y line required for this example was created as follows: Chinese Spring Wheat was crossed with A ⁇ ropyron elon ⁇ atum or another alien species such as Triticum thaoudar. Triticum monococcum or Triticum urartu and haploid plants selected from amongst the progeny. The haploids were treated with colchicine to induce chromosome doubling. By this method there were obtained the following addition lines: Chromosome 4 - Triticum urartu in male sterile Chinese Spring Wheat;
• Doubled haploid plants were then self-pollinated or, alternatively, backcrossed to one of the Z line wheats described above and plants bearing single alien additions were selected.
• the nuclear male sterile recessive Z-line of wheat, having the genotype ms.ms was crossed with a fertile maintainer line (designated the Y line), isogenic with the sterile line (ms.ms) but containing one alien chromosome capable of restoring fertility and carrying a blue aleurone colour marker derived from A ⁇ ropyron elon ⁇ atum genotype Ms.c) .
• the harvested seed was delivered to a commercial seed sorting machine which was tuned to discriminate between the differently coloured seed and to separate them physically. Using a Sortex 5000 (Trade Mark) seed sorting apparatus, the seed was separated into 35% white and 65% blue seed.
• Sortex 5000 Trade Mark
• Vulcan is an Australian wheat cultivar, and was converted to male sterility by backcrossing the recessive male sterile gene PROBUS into it.
• the progeny of blue seed was bulked and sent to be colour sorted.
• the result of this mechanical sorting was 65% blue seed and 35% white or non-blue seed. The purity of the non-blue seed was quite satisfactory.
• the translocation, CF24 was produced by crossing a wheat line carrying chromosome 4 of A ⁇ ropyron elon ⁇ atum (blue seed) to a wheat line carrying chromosome 4 of Triticum monococcum (blue seed) . Progeny were selected for male fertility and intensity of the blue aleurone. Fertile plants were crossed to male sterile Vulcan and male sterile Skua (Skua is an Australian wheat cultivar, male sterility was produced as described above.)
• the translocation CF22 was produced using the same process as described in Example 3. However, while chromosome 4 of A ⁇ ropyron elon ⁇ atum is included, male fertility restoration is provided by the short arm of chromosome 4 of Triticum monococcum (in the initial cross only the short arm of chromosome 4 of T. monococcum was present, ie, it was a telocentric addition) .
• a line designated 89-130(1) is a cross between male sterile Skua and CF22. This line has constantly produced very good blue seed and white seed in a 3:1 ratio in small populations.
• the translocation CF30 was produced in the same manner as CF22 and carries the same components; i.e. blue aleurone is provided by chromosome 4 of A ⁇ ropyron elon ⁇ atum and male fertility is provided by the short arm of chromosome 4 of T. monococcum. So the translocation is expected to be 4Ag/4mt, as in CF22.
• COMPARISON OF ADDITION AND SUBSTITUTION PLANT LINES A calculation can be made that compares the seed production in accordance with this invention, using the addition and substitution schemes. The calculation assumes that 1 plant produces 100 seeds, that 4000 seeds weigh 1 kg, and that 35kg/ha of seed produces 1 tonne of wheat grain. 1. Using an addition plant line, and the system shown in Figure 2, if it is assumed that the male transmission rate is 10%, and the female transmission rate is 20%, then after 6 generations of an addition line of hybrid wheat, the result will be about 77 tonne of heterozygous blue seed, and 213 tonne of white seed.
• a substitution line was created by the following procedure.
• a dark blue 43 chromosome line was created following the procedure described in part (a) of Example 1. These plants were self pollinated for 2 generations. Then they were crossed with male-sterile plants. The fertility of the resulting progeny and the segregation ratios for the blue allerone were checked. Those that had a classic Mendelian ratio were selected, as indicating a substitution line. Most likely, a centric fusion or Robertsonian translocation was responsible.

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Cited By (17)

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• 1990
  • 1990-07-17 GB GB909015671A patent/GB9015671D0/en active Pending
• 1991
  • 1991-07-17 WO PCT/AU1991/000319 patent/WO1992001366A1/en not_active Application Discontinuation
  • 1991-07-17 CA CA002087427A patent/CA2087427A1/en not_active Abandoned
  • 1991-07-17 AU AU82848/91A patent/AU651363B2/en not_active Ceased
  • 1991-07-17 EP EP19910913242 patent/EP0543837A4/en not_active Withdrawn

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