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Archive for the 'Plant breeding' Category

Breeding crops for organic agriculture

Organic farming is characterized by closed production cycles with minimum external input including the prohibition of the usage of synthetic pesticides. Weed control is optimized by crop rotation, mechanical treatments and competitive varieties. Pest and insects are controlled with predators, parasitoids, symbionts and resistant varieties. The nutrition of plants is provided with animal or green [...]

May 14th, 2011
Topic: Crop Science, Plant breeding Tags: None

Parental control and its implication on selection gain

The value of the parental control (c) depends on the recombination and the recurrent selection method. C is 0.5 if selected candidates are pollinated by selected and unselected genotypes. I.e. genotypes are selected at harvest. However, unselected genotypes contributed to the pollen cloud and thus also contributed to the following generation. Thus, desirable alleles are [...]

May 1st, 2011
Topic: Crop Science, Plant breeding Tags: None

Polyploidy

Polyploid genotypes have somatic cells which possess multiples of the basic chromosome sets (genome). 70 % of grass species and 23 % of the legume species are polyploid. The main causes of polyploidie are mutation and recombination. Further, environmental conditions favor the occurrence of natural polyploidie. The colder the environment and the less light the [...]

April 30th, 2011
Topic: Crop Science, Plant breeding Tags: None

Breeding scheme for potato

Vegetatively propagated crops: rape, strawberry, potato Breeding of clone cultivars, with example on potato. Potato is a vegetatively propagating plant. Each tuber is identical with the mother plant. Due to vegetative propagation genetic variation is usually caused only by mutations. Further, clones are highly heterozygous and exploit heterosis. However, progenies produced by selfing of clones [...]

April 26th, 2011
Topic: Crop Science, Plant breeding Tags: None

Index selection

Selection is carried out for a selection index calculated from the performance in several traits. For calculating an index the economic importance of the traits and the covariance of the traits need to be assessed. The advantage of index selection is that several traits are improved simultaneously. If the traits have the same economical weight, [...]

January 2nd, 2011
Topic: Crop Science, Plant breeding Tags: None

Heritability / Repeatability of a trait

Good performing plants are selected and are expected to generate good performing progenies. The problem is that this selection is based on the phenotype which is influenced by the genotype, the environment and the measurement error. The ratio between phenotypic to genotypic effects is very important to have as information about the trait. the larger [...]

December 23rd, 2010
Topic: Crop Science, Plant breeding Tags: None

Response to selection and selection efficiency

The genetic advance achieved through selection depends on the total variation, the repeatability of the trait (h²) and the selection pressure imposed. The selection pressure implies the proportion of the population selected. Even if the repeatability is high the genetic advance (genetic gain) would be small without a large genetic variation. With selection the genetic variation [...]

December 12th, 2010
Topic: Crop Science, Plant breeding Tags: None

Variance components and Estimation of genetic covariance between relatives

Variance components The variance of a random variable is the expectation of the squared deviation between a random variable (X) and its expectation (E). The expectation of a discrete random variable is obtained by weighting the possible outcomes X with their probabilities (in the case of a dice the probability is 1/6 for each outcome). [...]

November 26th, 2010
Topic: Crop Science, Plant breeding Tags: None

Mating designs in plant breeding

The application areas for mating designs are the selection of genotypes as variety parents in breeding of hybrid varieties and synthetic varieties and the estimation of genetic variance components for optimizing the design of breeding programs. The requirements for factoral and diallel designs are – each female must be able to be mated with several [...]

November 14th, 2010
Topic: Crop Science, Plant breeding Tags: None

Field designs for replicated trials

Replicated trials are applied for a reduced genotype set (n=300). To make sure that genotypes are selected properly one has to assure that the environmental effect on selecting decision is reduced. I.e. a variety can have a high yield in the leftern corner of the field, which might be genotypic effect, but can also be [...]

October 31st, 2010
Topic: Crop Science, Plant breeding Tags: None