A4*/B

A type of cross. The donor and recurrent parents are crossed, and the progeny crossed to the recurrent parent for multiple generations.

Advantages: Requres few plants, known and desirable recurrent parent phenotype is recovered, rapid, predictable, repeatable, breeding program can be independent of the environment.

Disadvantages: does not permit selection of new combinations of genes, linkage drag may be a problem.

A method of selection for self-pollinated crops following a cross, with no early generation selection. Developed by Nillson-Ehle. The simplest line development method. Progeny testing is performed only after acceptable homozygosity is achieved.

Advantages: No record keeping until F4, low labour, allows natural selection (biotic, abiotic, competition)

Disadvantages: Natural selection is not always an advantage: progeny are lost due to early sampling.

1. Cross parents to obtain F1.

2. Allow F1 to self-pollinate to produce F2.

3. Grow 1000 F2 plants, select the best plants or allow natural selection. Obtain a bulk of F3 seeds.

4. Grow 1000 F3 plants, select the best plants or allow natural selection. Obtain a bulk of F4 seeds.

5. Grow 1000 F4 plants, select best plants or allow natural selection to occur. Make single plant selections for F5 seeds.

6. First year trials of 100 F5 lines at 1 - 3 locations. Select the best 20 plants, save selfed seed.

7. Second year trials of 20 F6 lines at many locations. Select the best 5 plants, save selfed seed.

8. Third year trials of 5 F7 lines at many locations. Release a new cultivar.

Hordeum bulbosum method

A method of obtaining haploids in doubled haploid method.

A/B//C/D/3/E/F//G/H

A type of cross. A cross of two double crosses.

A/B//C/D

A type of cross. Two sets of parents are crossed, and the progeny crossed.

A method of selection for self-pollinated crops proposed by Bergner. Theoretical until the development of in vitro systems in the 1970's. Follows a cross, with no early generation selection. Haploid plantlets are produced by ovary culture, anther culture, chromosome elimination, microspore culture, or in vivo systems (spontaneous, semigamy, and polyembryony). Chromosomes are doubled by cochicine to produce homozygosity.

Advantages: Quick, small population size, doubled haploids are extremely uniform, selection is very efficient, favourable linkages are preserved.

Disadvantages: Specialized personnel and infrastructure are required, efficiency depends on genotype, and unfavourbale linkages are preserved.

1. Cross parents to obtain F1.

2. Use lab methods to double the chromosome number in F1 to produce doubled haploid F2.

3. Grow F3 plants and evaluate and select: homozygosity is achieved.

A method of selection for self-pollinated crops using existing variation. Plants are chosen from a genetically diverse population on the basis of phenotype. Seed is composited without progeny testing. The easiest method of selection in self-pollinating crops. The end product doesn't differ in performance from the original population, but it is more uniform. Develop a new culivary by improving average performance of the population.

Objectives: Purify a mixed cultivar or plant population by propagating plants with similar phenotype, and develop a new cultivar by improving average performance of the population.

Similar to SSD, but instead of one, 2 - 3 seeds per plant are used for the following generation. Progeny from individual lines is maintained separately during each generation of increase.

Advantages: Reduces selection efforts prior to F6, easy, no natural selection, well suited to winter/off-season nurseries.

Disadvantages: More plants than SSD, no elimination of undesirable alleles early on, no natural selection, genetic combinations may be lost if population sizes are too small.

A method of selection for self-pollinated crops, following a cross, with early generation selection. Follows hybridization. Progeny testing is an essential feature. Breeder maintains a family structure by growing progeny of each selected single plant in progeny rows. Single plant selections in early generation, and row selection when homozygosity is reached. Was popular in the 80's and 90's, but was replaced with bulk method.

Advantages: Traces the lines of each cultivar back to an F2 plant (allows breeders to exploit variation within prior generations), artificial selection can be imposed in each generation, breeder can use their "breeder eyes".

Disadvantages: Additional work is needed to keep track of pedigree lines, more resources are required.

1. Cross parents to obtain F1.

2. Allow F1 to self-pollinate to obtain F2.

3. Grow 1000 F2 plants. Screen for traits with high heritability. Save selfed seeds from 200 plants.

4. Grow 200 F3 lines in progeny rows. Select the best 50 lines. Save selfed seeds from the best 1 - 2 plants in each row.

5. Grow 50 - 60 F4 lines and sublines. Select the best 15 lines. Save selfed seeds from the best 1 - plants in each row.

6. Trials of 15 T5 lines at 2 - 3 locations. Select the best 8 lines. Saved self seeds.

7. Trials of 8 F6 lines at more locations. Select the best 4 lines. Select selfed seeds.

8. Trials of 4 F7 lines at more locations. Release new cultivars.

A method of selection for self-pollinated crops using existing variation. Isolating pure lines from a mixed population.

1. Grow 1000 plants, screen for traits with high heritabilty, save selfed seeds from 100 selected plants.

2. First year trials of 100 pure-lines at 1 - 3 locations. Select the best 20 pure lines.

3. Second year trials of 20 pure lines at many locations. Select the best 5 pure lines.

4. Third year trials of 5 pure lines at many locations. Release new cultivars.

Convergent cross

A type of cross. All possible ways of a conical cross between 8 parents is tried for 8 sets of F1.

The portion of individuals in a population which are heterozygous.

= (½)^m

m = the number of generations of self-fertilization = (generation number - 1)

A/B

A type of cross. Two parents are crossed.

A method of selection for self-pollinated crops proposed by Goulden. Follows a cross, with no early generation selection. A form of bulk method. Progeny testing is postponed until acceptable homozygosity is reached. Selections can be as good as other systems.

Advantages: Each F2 plant is represented in the progeny test. The varietion of F2 is well represented, and advese effect of natural selection is minimized. Not much space is required: possible to grow multiple generations indoors.

Disadvantages: No selection during early generations, harvest may be more difficult than conventional bulk.

1. Cross parents to obtain F1.

2. Allow F2 to self-pollinate to produce F2.

3. Grow 1000 F2 plants. Save one seed from each of 150 selected plants. Bulk the F3 seed.

4. Grow 150 F3 plants. Save one seed from each plant. Bulk the F4 seeds.

5. Grow 150 F4 plants. Save F5 seeds from 100 individual plant selections. 

6. First year trials of 100 F5 lines at 1 - 3 locations. Select the best 20 plants. Save selfed seeds.

7. Seocnd year trials of 20 F6 lines at many locations. Select the best 5 lines. Save selfed seeds.

8. Third year trials of 5 F7 lines at many locations. Release a new cultivar.

A/B//C

A type of cross. Two parents are crossed, and the progeny are crossed to a third parent.