Lecturer: Vu Thi Thu Hien, Ph.DDepartment of Genetics and Plant Breeding

RECURRENT SELECTIONCHỌN LỌC CHU KỲ

Group 10: Le Thu Hoai Pham Thi Lua Do Thi Nam Trang Bui Minh Thai Nguyen Thi Mai

OUTLINE Overview of recurrent selection (RS)

Concept ObjectiveResult Applications

Circle of selection process: 3 components Methods of improvement

Intra-populationInter-population

OUTLINE Intra-population

Recurrent phenotypic selectionRecurrent genotypic selection

○ Half-sib progenies○ Full-sib progenies○ Selfed Families○ RS for general combining ability○ RS for specific combining ability

Inter-population ( Reciprocal recurrent selection)Reciprocal half-sib selectionReciprocal full-sib selection

Concept Cyclic and systematic selection of desirable

individuals From a population: base, source or cycle 0

population By recombination of selected individuals Form a new population: cycle 1, cycle 2, and

so forth

The process routinely occurs in cultivar development program

Objective and result

Objective: Improving the performance of populations for one or more traits of interest

Result: Superior to original one in Mean performancePerformance of best individualsIncreasing frequency of desirable genes Without reducing genetic variability present

in population

Applications

Used to establish a broad genetic base in breeding program because of multiple opportunities for intermating.

Applied to legumes (e.g., peanut, soybean), grasses (e.g., maize, barley, oats)

Selection process

Development of a base population

Best performance possible for characters of interest

Array of different ancestries Number of parents should be used Number of intermating generations to form

Recurrent phenotypic selection The earliest method improving cross-

pollinated species, simple recurrent selection

Individual plant per se or clonal progeny By visual inspection or measuring the

character of interest Test crosses are not made, no tester is

used Identified individuals form a new population

and next cycle begin

Recurrent phenotypic selection Limitations :

Restricted to characters with sufficiently high heritability

Variability among plants caused by microenvironmental variation

Examples Spraque and Brimhall (1950): oil content of

corn kernelGardner (1961): Gridding on maize

Recurrent Half-Sib Selection Evaluation of individuals through the use of

their half-sib progeny. The general procedure for a cycle of

selection:To cross the plants being evaluated to a common

tester Evaluate the half-sib progeny from each plant Intercross the selected individuals to form a

population.

Alternative procedures for recurrent half-sib selection

Tester Parents selected Seed for intercrossing

Population Female Half-sib seed

Population Male and Female Half-sib seed

Population Male and Female Selfed seed or clones

Outside Male and Female Selfed seed or clones

Recurrent Full-Sib Selection The testing of paired-plant crosses.

The seeds from two individuals, rather than one, are used for testing and to form the new population.

Recurrent Full-Sib Selection

Season 1 Crossing between pairs of selected plants in a population (cycle 0)

Season 2 The full-sib families are evaluated in replicated tests and the superior families are selected.

Season 3 Remnant full-sib seed is used to intercross the selected families. The intercrossed seed that is harvested (cycle 1)

Season 4-6 Next cycle in the same manner

Testing of paired-plant crosses

Recurrent Selection Among Selfed Families

Used in both self- and cross-pollinated crops

Testing of lines after one or more generations of selfing

Followed by intercrossing of individuals to form the new population.

Procedure of RS among selfed families

Season 1 S0 plants from the population are selfed to produce S0:1 lines.

Season 2 S0:1 lines evaluated, best lines selected

Season 3 Remnant S1 seed used to intercross selected lines, producing the Cycle 1 population with new S0 plants

Season 4 Next cycle begins

RS for General Combining Ability Proposed by Jenkins(1940) for

improving open-pollinated maize cultivars

Use of population as tester, selection of superior half-sib families based on replicated tests, selfed seed for intercrossing selected individuals.

Broad genetic base tester, performance in a group of test crosses (hybrids) refers differences in GCA

RS for GCASeason 1 Select best individuals (base population) , selfing

Season 2 Selfed seeds are intercrossed tester, best individuals are selected by evaluation of yield and traits of interest.

Remnant selfed seed put in storage for next cycle

Season 3 Next cycle begins

RS for Specific Combining Ability Proposed by Hull(1945) Use of an inbred tester: narrow genetic

base Variation in test-crosses performance

ascribed to differences in SCA Develop an improved population or

inbred lines from it that could be crossed with the tester to produce commercial seed

RS for SCASeason 1 Best individuals are selfed, and simultaneously crossed

with inbred tester

Season 2 Selection and evaluation superior half-sib families in replicated experiments at at least 2 isolated areas

Season 3 Selected plants are intercrossed to form a cycle 1 population for each using the remnant selfed seed

Season 4-6 Next cycle in the same manner

Methods of Interpopulation Improvement Reciprocal recurrent selection (RRS) is a

cyclical breeding procedure designed to improve the cross of two populations(A&B) from different heterotic groups by using both general and specific combining ability.

A,B: heterozygous and genetically unrelated

A used as the tester to evaluate individuals in B, and vice versa

Reciprocal Half-Sib Selection Proposed in 1949 by Comstock and

colleagues

Procedure of reciprocal half-sib selection

Season 1 Individual plants (e.g., 100) from each cycle 0 population are selfed and outcrossed to several (e.g., 6) randomly chosen plants from the opposite population (tester) Generate ½ sib families and selfed seed put in storage

Season 2 100 ½ sib families from each population are evaluated in replicated testsTop 10 are identified for each A and B

Season 3 10 selected plants are intercrossed to form a cycle 1 population for each using the selfed seed produced in season 1.

Season 4 Begin next cycle using Cycle 1 seed of each population

Reciprocal Full-Sib Selection It was described independently by maize

breeders in Iowa and Nebraska (1967)

Desired outcome is commercial hybrid seed

Procedure of reciprocal full-sib selection

Season 1 200 phenotypically desirable S0 plants in Pop A paired with 200 from Pop B. Each plant is both selfed and crossed to produce S1 and full-sib seed. Selfed seed can be stored for intercrossing of desirable parents and also advanced to develop inbred lines

Season 2 200 full-sib families from each population are evaluated in replicated tests;

Superior 10% of pairs are selected

Season 3 Intercross selfed seed of top 20 individuals from each population

Intercrossed seed of A and B represent Cycle 1 populations

Season 4 Begin again.

References

Fehr, W.R. 1991. Principles of cultivar development: The theory and technique, vol 1. 15:172- 197.

R.W. Allard. 1960. Principles of plant breeding. 23: 282- 302.

V.D.Hoa. 2005. Giáo trình chọn giống cây trồng. 6: 77- 90